NitroPack Documentation

NitroPack is a powerful optimization tool that will help speed up a WordPress^® site on WP Engine.¹ With just a few clicks, it enhances the website’s performance by compressing, caching, and optimizing resources.

NitroPack can be purchased for most Shared and Premium plans from the Products page. At this time it cannot be added to WP Engine Headless Platform plans. NitroPack product pricing is based on number of licenses.

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Enable

To enable NitroPack on an environment: 

1. From the User Portal, choose Products in the main sidebar menu
2. Click NitroPack under Your products
   • Access this page directly at: https://my.wpengine.com/products/nitropack
3. Click Add environments
   
4. (Optional) It’s recommended to test NitroPack on a Staging or Development environment before applying it to Production. Click No license required to view Staging and Development environments. Note that the performance benefits on Stg/Dev will not be as great, and testing here should simply be done for overall compatibility with the Production environment. NitroPack must be purchased for the account before the No license required option will be available.
   
5. Check the box(es) of the environment(s) to enable NitroPack on, read and agree to the Terms and Conditions, and click Install
   • You will see a popup progress bar while the NitroPack plugin is being installed on the selected environments. Wait for this to finish to see the next steps.
6. Click Preview Site next to an environment name to preview how the site will display when NitroPack is enabled.

• This will open the environment’s url for previewing with the ?testnitro=1 query string appended to it.
  • example: https://mynewsite.wpenginepowered.com?testnitro=1

6. If there are no issues on the preview, continue to the next step. If there are issues on the site preview you can choose a different Optimization Mode with the directions below or enable NitroPack and then try Custom Settings.
   • Expand the dropdown to and select one of the other optimization modes. This will make some changes that might work better for the site.
     • Optimization Modes (view table under Optimization Mode Settings below for more details):
       • Standard: Standard optimization features. Ideal choice for maximum stability.
       • Medium: Adds image lazing loading and uses built-in browser techniques for loading resources.
       • Strong: Includes smart resource loading on top of Medium optimizations.
       • Ludicrous: Applies deferred JS and advanced resource loading for optimal performance.
         
     • Click Preview Site again. (If the site preview is still open, refresh the page to see the changes.)
     • This process can be repeated through the available configurations until the site displays properly. Once satisfied, proceed to the next step.
7. Choose your enablement option. You have the option to choose whether you want to enable Google Lighthouse score monitoring during this step. You can change this later for each environment from the NitroPack product page later if you change your mind. If you don’t want Google Lighthouse score monitoring, then click the Enable without monitoring button. If you do want Google Lighthouse score monitoring then click the Enable selected button.
   

The plugin will be automatically installed on the selected environment(s) and no further configuration is required. Performance improvements may take some time before becoming visible.

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Features

NitroPack is a performance WordPress plugin that automatically handles cloud-based optimization of the frontend of your website. Below is a list of current features.

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Lazy Load Images

The lazy load feature will only download images that currently fall within the browser viewport, on initial page load and downloads other images later when necessary. This speeds up the initial page load and saves on bandwidth.

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Size Images Preemptively

Preemptive Image Sizing is a smart optimization technique that ensures all images on your website have explicit height and width attributes before they load. This prevents layout shifts and helps maintain a smooth, stable user experience.

By setting proper dimensions, browsers can allocate space for images before they fully load, reducing Cumulative Layout Shift (CLS)—a crucial Core Web Vitals metric.

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Lazy Load Iframes

Delays loading of iframes until they come into the viewport.

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Lazy Load Self-Hosted Videos

Delays loading of YouTube and Vimeo videos until they come into the viewport.

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Image Optimization

Images are the largest contributor to page weight. Furthermore, unoptimized images can account for 2-4x more data usage, slower loading times, and bad page experience.

The solution to having an image-rich website and achieving web performance that Google and your users love is two-fold:

• Apply compression
• Serve images in next-gen format

Enabling NitroPack’s Image Optimization setting will take care of your images, keeping their high quality while massively boosting your page load times.

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Animated Image Optimization

Optimizes animated GIFs and PNGs, reducing size while maintaining quality.

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Adaptive Image Sizing

Adaptive Image Sizing is a preemptive optimization of images, making them match the dimensions of the containers they’re displayed in for desktop, mobile, and tablet devices. Faster-loading images significantly improve user experience and can positively impact metrics like bounce rate and page loading time.

Adaptive Image Sizing automatically resizes your website images to suit the visitor’s device and screen resolution without compromising on quality. This results in enhanced website performance and reduced loading times, making AIS particularly beneficial for image-heavy content.

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Video Facades

Video Facades is a feature within NitroPack designed to improve page load times by replacing embedded videos (like those from YouTube or Vimeo) with a static image (thumbnail). This means that instead of loading the entire video player and its resources when the page loads, only the thumbnail is loaded initially. The video content is loaded and activated only when the user interacts with the placeholder image, ensuring a smoother and faster browsing experience.

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LCP Preload

Improves your Core Web Vitals by automatically identifying and preloading the LCP (Largest Contentful Paint) element.

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Optimization Mode

NitroPack lets you choose between predefined optimization modes to balance stability and performance. The modes range from Standard and Medium (the most stable) up to Strong and Ludicrous (the default, most aggressive mode). You can also use Custom Mode to freely tweak individual settings. View the settings enabled for each mode below.

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Test Mode

The Test Mode lets you test NitroPack’s features in an isolated environment. That way, you can experiment without affecting your visitor’s experience.

When you turn the Test Mode on, it disables NitroPack for your website. While this mode is active, you can access the test (optimized) version of any page by adding ?testnitro=1 to its URL, like the screenshot below. Your website remains up and running for your site visitors as if NitroPack is disabled.

Any changes you make while in Test Mode affect only the test pages. This lets you experiment with settings without affecting the user experience.

Just remember that after disabling the mode, all changes will be transferred to your live website. If you don’t want that, make sure to reverse any changes you made while in Test Mode before turning it off.

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Cache Warmup

The cache warmup feature preemptively optimizes and caches your pages without having to wait for traffic to a page for the cache to be updated. It will also keep pages optimized and cached after automated cache purge events. This assures that the first visitors after automated cache clearing events receive a fast page load experience.

To enable cache warmup:

1. From the Products page in the User Portal select NitroPack or visit the following url:
   https://my.wpengine.com/products/nitropack
2. Click the three dot button to the right of an environment and select Settings
3. Scroll down to the Cache warmup section and click Enable
   
4. Choose either Standard or Sitemap
   • Standard will scan your home page to identify URLs of important pages to cache.
   • Sitemap gives you the option to input your sitemap url to identity all pages in your sitemap index for caching.
     
5. If you chose Sitemap then input your full sitemap URL in the box. If you don’t know your URL, check with your development team or your SEO plugin author. 2 example sitemap URLs that are used by SEO plugins are:
   • https://yoursite.com/sitemap_index.xml
   • https://yoursite.com/sitemap.xml
6. Click Save to finish enabling the cache warmup feature.

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Remove Render-Blocking Resources

Render-blocking resources are resources that prevent a web page from being rendered and displayed to the user until they are fully downloaded and processed by the browser. These resources include CSS, JavaScript, and fonts that are necessary for the layout, styling, and functionality of the page.

Below are some examples of the multiple strategies NitroPack uses for delaying, optimizing, or removing render-blocking resources.

1. Generate Critical CSS
2. Remove unused CSS
3. Combine CSS
4. Combine JavaScript
5. Font Subsetting

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Delayed Scripts

Execute specific scripts with a delay (about 6500ms after page load) to prioritize other important user experience elements.

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Combine JavaScript

Combines your JavaScript files into just one file to reduce network requests.

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Optimize Google Tag Manager

Improves page performance by optimizing how GTM loads and runs.

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Keep HTML Comments

Preserves your HTML comments and prevents them from being automatically removed during optimization.

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Minify JSON for Linking Data

Automatically removes unnecessary characters from JSON files, resulting in compact and efficient files.

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HTML Normalization

Normalizes your HTML prior to optimizing it, automatically resolving issues with misplaced elements in the DOM tree.

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Generate Critical CSS

Optimizes the delivery of critical above-the-fold CSS for faster rendering.

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Custom CSS

Add your own CSS styles and override default themes to fine-tune the styles of site elements during page loading.

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Remove Unused CSS

Finds CSS rules that aren’t used on the page and reduces them to lower total downloaded bytes.

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Combine CSS

Merges multiple CSS files into a single file to reduce HTTP requests.

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Extract Large Inline CSS

Inline CSS over 3KB is moved to an external file to prevent render-blocking.

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Override Font Rendering Behavior

Lets you override the default browser behavior by selecting specific font-display values.

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Font Loading Strategy

Provides two techniques (“Native” and “Onload”) for fetching fonts to prevent unwanted layout shifts and improve page load times.

Native (enabled by Default)

Also known as “Font Preloading technique”, it ensures fonts start loading early in the page lifecycle, reducing the chances of the “flash of invisible text” (FOIT) or “flash of unstyled text” (FOUT). By adding a preload link in the head section, you instruct the browser to fetch the font resources as soon as possible.

Onload

Similar to the previous method, however, the fonts are reconfigured to load after the onload event. That means that the fonts will be applied to the page after it’s loading.

With this option, we improve the LCP and FCP metrics.
Please note that font flickering may be seen during the page load. That is valid for websites that don’t use Web Safe Fonts.

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Font Subsetting

NitroPack’s font subsetting feature automatically creates a subset version of the original font file by removing all unused glyphs (in many cases, it is hundreds or even thousands of them).

Depending on the number of glyphs removed, it can reduce their size drastically, making them much faster to load by the browser.

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Font Compression

Upgrades your font compression to the WOFF2 format, which can reduce font sizes by up to 50%.

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Optimize Google Hosted Fonts

Once enabled, the “Optimize Google Hosted Fonts” feature overrides font rendering behavior, focusing specifically on Google-hosted fonts.

NitroPack’s innovative font optimization technology enables a smoother, visually appealing, and efficient browsing experience by streamlining how Google Fonts are rendered.

With a ‘swap’ rendering strategy in place, a fallback font is promptly displayed. This is then subsequently swapped with the desired Google Font once fully loaded, eliminating delays associated with blank text or invisible fonts during loading and maintaining an engaging user interface.

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Cache Expiration Time

With this setting, you can control for how long our service holds your cached pages. When a cached page expires, a new Page Optimization is required to re-create the cache. By default, the cache expiration time is set to 2592000 seconds (86400 seconds = 1 day).

You can change this using our “Cache expiration time” feature:

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Optimize-Only URLs

When you first start using NitroPack, you might like to test it only on a few pages. With the “Optimize only” URL feature, you can specify a list of included URLs you’d like to be optimized.

Important Note: If you use this feature, only the Included URLs and no others will be optimized.

1. Go to Cache Settings >> Cache
2. Find the Optimize-only URLs feature and enable it (click the toggle on the right).
3. Enter the URL of the page you wish to include.
4. For multiple pages, enter each one on a new line.
5. Finally, click the Save button on the top right to save your changes.

Using Wildcards

With wildcards, you can include a group of pages with one entry. For example, here’s how you can include all pages of your blog post, assuming they’re set up as child pages with the/blog/article-name URL structure.

You can use the following pattern with your domain in place of yoursite.com:

https://yoursite.com/blog/*

This will include the page /blog/ itself, and all the pages with /blog/ in the URL, for example: /blog/first-article/ and blog/another-article.

You can also use wildcards to include all URLs containing a specific word. For example, to include all category URLs (assuming they all have “category” in the URL path):

*category*

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Minify Resources

Minification removes whitespace, comments and other unnecessary symbols from code files, reducing file size and ensuring a faster download time.

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Optimize Ads

You can manually turn on the “Optimize Ads” feature if ads are affecting your performance metrics.

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Dynamic Queue

Optimizes your most-visited pages first to deliver faster performance where it counts.

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Instant Cache Reoptimize

Automatically refreshes cache when it expires to keep your site optimized at all times.

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Cache AJAX URLs

Captures the output of AJAX requests and saves them in an HTML file for quick reuse to make them load faster.

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Ignored Parameters

Specify URL tracking parameters that NitroPack should ignore when optimizing your website to prevent redundant cache files.

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Include The Default Ignored Parameters

Automatically ignore a long list of standard tracking parameters.

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Must-Include Headers

Forces NitroPack to check for custom or non-standard headers (like security headers) during optimization and preserve them.

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Excluded URLs

Specify a list of URLs you would not like to be optimized, either individually or using wildcards.

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Excluded Resources

Prevent NitroPack from optimizing specific CSS, JavaScript, Font, or Image files so they load directly from their original sources.

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Dynamic Content Cookies

Allows NitroPack to create and serve separate, customized cache files for each HTML variation based on specific dynamic PHP cookie names and values.

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Excluded From Optimized Cookie Names

Allows you to serve non-cached content to specific users based on their cookies (e.g., logged in users or active shopping carts).

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Additional Domains

Specify additional domain names pointing to the same website.

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Cart Cache

Cart Cache is a caching feature inside the NitroPack plugin that enables fast browsing in a WooCommerce store with items in the cart.

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Background Purge

Replaces old cache only after new cache is ready so users always get optimized content and a fast experience.

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Optimize Interactive Elements

Improves INP by reducing the time it takes for the page to react to clicks and taps.

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Smart Cache Invalidation

Smart cache invalidation automatically clears and updates cached content that is related to a page that you have just purged.

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After purchasing and enabling on the environment of choice via the User Portal, the WP Engine NitroPack WordPress plugin will be installed automatically.

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NitroPack Statuses

Being enabled – NitroPack is currently being provisioned for this site. This environment counts toward the account license limit.

Failed to enable – NitroPack failed to be installed on the environment. This environment is not counted towards the account license limit.

Being disabled – NitroPack is currently being removed from this environment. This is typically faster than enabling. This environment counts toward the account license limit.

Failed to disable – NitroPack is not currently installed on the environment. This environment does not count toward the account license limit.

Missing or inactive – NitroPack is active but Smart Plugin Manager has not yet detected the plugin. Click Refresh to update plugin information.

Syncing plugin data – NitroPack shows this message during the enabling process and is related to the missing or inactive section above. After the NitroPack installation, we schedule the SPM sync to update information about the plugins status. This will take some time before the sync finishes.

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NitroPack Cache

NitroPack compresses and optimizes files, then stores those in an independent cache. Purging this cache can help with visual discrepancies and displaying recent updates.

To purge NitroPack cache when logged into your website:

1. Locate NitroPack in the top menu bar of the wp-admin
2. Select the option you would like to use:
   
   • Purge Entire Cache: Select this option to purge the cache for the entire website. This option is visible from both the front end and the wp-admin area of your website.
   • Purge Current Page: Select this option to delete the page you are currently viewing from the cache. This means your website visitors will immediately see the updated content, however, it will not be optimized until NitroPack prepares the newly optimized content. Usually, this takes between a few seconds to a few minutes. This option is only visible from the front end of your website.
   • Invalidate Current Page: Select this option to mark the cached content on the page you are currently viewing as “stale,” but keep serving it until newly optimized content is available. As a result, visitors will always see optimized content, even though it may be outdated for a short while. This option is only visible from the front end of your website.

NitroPack cache can also be cleared from the User Portal:

1. From the User Portal, choose Products in the main menu
2. Click NitroPack under Your products
   • Access this page directly at: https://my.wpengine.com/products/nitropack
3. Next to the environment, click the 3 dot menu icon
4. Select Clear caches

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Lighthouse Events

We’re now showing Events on the Lighthouse Performance graph. The graph shows on the Performance page for an environment. The Events will show for an environment if you have our NitroPack product, and Lighthouse Monitoring both enabled for the environment.

The Events are updates to the site which you can take into consideration when investigating score changes on a specific day. Also consider reviewing Events on days prior to a score change to account for the timing of the daily score measurement and different types of cache, etc.

You’ll see a dotted vertical line with a small circle at the bottom, when there is a day with Events on the graph. If you hover on the circle you’ll see the hover card with the list of events as shown below.

If there is a long list of Events, you can click Show all events to get a pop-out sidebar with the full list.

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Monitoring Settings

You can now get notifications when your Google Lighthouse scores change. You can customize the notifications by environment or in bulk for multiple environments, and receive notifications through the WP Engine User Portal, email, or the Slack app.

The two thresholds you can choose from are the score dropping by a number of points, or the score dropping below a number. You can customize each threshold for all of the Lighthouse score categories (Performance, Accessibility, Best practices, SEO). You can also choose which of the 4 categories you want to track.

Default Settings

Score drops by a specified number of points

• Performance – 6
• Accessibility – 3
• Best practices – 4
• SEO – 5

Score falls below a specified score

• Performance – 50
• Accessibility – 50
• Best practices – 50
• SEO – 50

Customize Settings

1. In the User Portal go to the Products page in the left sidebar
2. Click on NitroPack under Your products
3. Check the box next to one or more environments that you want to share the same monitoring thresholds
4. Click the Monitoring settings button in the top right of the table
   
5. Review the Drop in score and Score falls below threshold sections
6. Check the box next to each score category that you want to monitor in each section
7. Adjust the numbers from 1-99 for each score category 
8. Click the Save button in the bottom right
   

Lighthouse Score Monitoring Column

We’ve added a new Google Lighthouse Score monitoring column to the main table view of the NitroPack products page. This lets you see an overview of which environments have monitoring enabled and statuses of score changes. You can also get more details in a tooltip when you hover on the status for each environment.

1. In the User Portal go to the Products page in the left sidebar
2. Click on NitroPack under Your products
   

Set Notifications

To choose your notification method you can navigate to the Notification Settings page. In addition to using the link you can also navigate there by using the Go to notification settings button on the Monitoring settings page, or click the Bell icon in the top right of the Portal, and then click the Gear icon.

Then choose any of the 3 types of notifications outlined below, Portal, Slack, and Email.

Add Portal Notifications

1. Click the dropdown arrow to the right of the Portal option
   
2. Scroll down to the NitroPack section
3. Click the Warning notification type to get notifications about score changes
   • Notification choices will be grayed out when they are not turned on. Clicking the box will enable it.

Add Slack Notifications

1. Click the dropdown arrow to the right of the Slack option
   
2. If you have not yet connected Slack, click the Add to Slack button and you’ll be taken from the Settings tab to the Integrations tab. If you have connected Slack already then you can skip to step 7 to Create Policy.
   
3. Click Create Integration
   
4. Click the Add to Slack button again in the popup window
   
5. Then in the next window, approve the permissions to connect to Slack 
6. Then return to the Settings tab and click the dropdown arrow to the right of the Slack option again
   
7. Click Create policy
   
8. Choose the Slack group that you want to send notifications to and then click Next
   
9. Choose a public Slack channel to send notifications to and click Next
10. Scroll down to the NitroPack section
11. Click the Warning notification type to get notifications about score changes
    • Notification choices will be grayed out when they are not turned on. Clicking the box will select it.
12. Scroll to the bottom of the popup window and click Create Policy in the bottom right

Add Email Notifications

1. Click the dropdown arrow to the right of the Email option
   
2. Click the Create policy button
   
3. Search for users and check the box next to each that you want to receive email notifications
   
4. Scroll down to the NitroPack section
5. Click the Warning notification type to get notifications about score changes
   • Notification choices will be grayed out when they are not turned on. Clicking the box will select it.
6. Scroll to the bottom of the popup window and click Create Policy in the bottom right

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Troubleshooting

If issues are caused by NitroPack, it is recommended to try these steps:

1. Check for conflicting features and plugins as well as service limitations.
2. Confirm if NitroPack is causing the issue by bypassing it’s cache. Append the ?nonitro parameter to a given URL to test. (example: domain.com/page?nonitro)
3. If media (images, video, etc) are having display issues, exclude the asset type or page from NitroPack’s cache.
4. Change NitroPack’s optimization mode to see if less intrusive caching settings resolve the issue.

Optimization Modes

If you see issues when enabling NitroPack, several optimization modes are available to make changes that may work better for the site. If you prefer to make custom changes, see Custom Settings.

1. Open the NitroPack page in the User Portal
2. Locate the environment and click the 3 dot menu icon
3. Click Troubleshoot environment
4. Expand the dropdown and select one of the other Optimization Modes. This will make some changes that might work better for the site.
   • Optimization Modes:
     • Standard: Standard optimization features. Ideal choice for maximum stability.
     • Medium: Adds image lazing loading and uses built-in browser techniques for loading resources.
     • Strong: Includes smart resource loading on top of Medium optimizations.
     • Ludicrous: Applies deferred JS and advanced resource loading for optimal performance.
       
5. Click Preview Site again. (If the site preview is still open, refresh the page to see the changes.)

This process can be repeated through the available optimization modes until the site displays properly. Once satisfied, be sure to save the changes.

Features Enabled for each Optimization Mode

Setting	Standard	Medium	Strong	Ludicrous
1. Add HTML preconnects	ON	ON	ON	ON
2. Minify resources	OFF	ON	ON	ON
3. Combine JavaScript	OFF	OFF	OFF	OFF
4. Combine CSS	OFF	ON	ON	ON
5. Combine CSS > Merge screen and all media styles	OFF	ON	ON	ON
6. Generate critical CSS	OFF	ON	ON	ON
7. Generate critical CSS > Remove @font-face rules from the critical CSS	OFF	ON	ON	ON
8. Remove Unused CSS	OFF	OFF	OFF	OFF
9. Remove render-blocking resources	OFF	ON	ON	ON
10. Remove render-blocking resources > Use resource loader script	OFF	OFF	ON	ON
11. Remove render-blocking resources > Delay loading of non-critical resources	OFF	OFF	OFF	ON
12. Remove render-blocking resources > Resource loading strategy	Styles First	Styles First	Styles First	Styles First
13. Automatic image lazy loading	OFF	ON	ON	ON
14. Image lazy loading > Size images preemptively	OFF	ON	ON	ON
15. Image lazy loading > Lazy load iframes	OFF	ON	ON	ON
16. Image optimization	ON	ON	ON	ON
17. Image optimization > Image quality	100%	80%	80%	80%
18. Override font rendering behavior	OFF	OFF	ON	ON
19. Override font rendering behavior > Select font-display value			swap	swap

SETTING DEFINITIONS:

1. Add HTML preconnects
   Preconnecting alerts the browser that you intend to establish a connection with an important domain and that process should start as soon as possible. Reducing the time it takes to establish a connection results in better performance. This setting is always enabled and we don’t have an interface for it yet.
2. Minify resources
   Minification removes whitespace, comments and other unnecessary symbols from code files. This reduces file size, ensuring a faster download time.
3. Combine JavaScript (JS)
   Combining multiple JS files into a single file reduces the number of network requests the browser has to make. As a result, the browser finds and downloads everything it needs to render the page faster.
4. Combine CSS
   Combining multiple CSS files into a single stylesheet reduces the number of network requests the browser has to make. As a result, the browser finds and downloads everything it needs to style the page faster.
5. Combine CSS > Merge screen and all media styles
   This option makes sure that NitroPack treats @media screen and @media all values the same. This prevents the creation of unnecessary CSS files.
6. Generate critical CSS
   Generate critical CSS means prioritizing the CSS responsible for styling above-the-fold content. Rendering above-the-fold content quickly improves a page’s actual and perceived performance.
7. Generate critical CSS > Remove @font-face rules from the critical CSS
   @Font-face rules specify a custom font, which can be loaded locally or from a server. Removing these rules results in slower font loading but faster First Meaning Paint (FMP).
8. Remove Unused CSS (RUCSS)
   RUCSS finds CSS rules that aren’t used on the page and reduces them. By reducing unused CSS, this feature lowers the total number of bytes that have to be downloaded and helps browsers start rendering content faster.
9. Remove render-blocking resources
   By default, JavaScript and CSS files are render-blocking because browsers must load, parse and execute them before rendering the page. This can slow down page load significantly. NitroPack prevents this by rearranging and repositioning these blocking resources.
10. Remove render-blocking resources > Use resource loader script
    Our resource loader rearranges the way resources are fed to the main thread. This is done to take advantage of modern CPU’s multi-core nature by offloading tasks away from the main thread.
11. Remove render-blocking resources > Delay loading of non-critical resources
    By default, NitroPack’s Ludicrous Mode lazy loads JS execution until user interaction is detected. Lazy loading JS helps browsers start painting content (HTML, CSS) faster. In a lot of cases, this is crucial for avoiding page abandonment.
    Important Note: This setting is not a good fit for websites that heavily rely on JavaScript for displaying content. Before applying the setting on your site, we advise you to test it with the Test Mode.
12. Remove render-blocking resources > Resource loading strategy
    This option lets you choose between prioritizing styles (CSS) or scripts (JS). Prioritizing styles is the safer option, while loading scripts first can provide better performance but isn’t suitable for all websites.
13. Image lazy loading
    Lazy loading helps browsers only load the images that visitors are currently looking at. Doing this helps prioritize critical images over non-critical ones, resulting in a much lower initial page weight.
14. Image lazy loading > Size images preemptively
    Preemptive image sizing tells the browser how much space to allocate for each image in advance (without using width and height attributes). As a result, the browser can render the page faster and avoid potential layout shifts.
15. iFrames Lazy load
    Again, lazy loading help helps browsers only load resources that visitors currently need. This option does the same thing, only for iFrames instead of images.
16. Image optimization
    Image optimization reduces image file size via compression. It also converts images to WebP while keeping the original image in place as a backup.
17. Image optimization > Image quality
    This option lets you adjust the quality of optimized images. As you increase the number, the quality becomes better, but the image file also becomes larger. Allowed values are between 1 and 100. You can learn more about image quality and compression levels here.
18. Override font rendering behavior
    The font-display CSS rule determines how the browser should display fonts based on when they’re downloaded. This option lets you override the default behavior by selecting from one of the five values below.
19. Override font rendering behavior > Select font-display value
    You can choose between five values for the font-display rule – auto, block, swap (the default), fallback, optional. Each value can be helpful in specific cases. You can read more about the font-display values here.

Custom Settings

You can now make custom changes to settings for NitroPack. When making a custom change you will automatically be switched to the Custom optimization mode.

To view and edit settings for NitroPack:

1. Go to the Products page in the User Portal
2. Click on NitroPack under Your products
3. Click the three dot button to the right of any environment you want to adjust
4. Click Settings
   

This will take you to the settings page inside of NitroPack where you can choose from the categories in the left sidebar to adjust individual settings.

The main settings are explained below the Optimization Mode Settings table above.

Exclusions

Exclude full pages that you don’t want to be optimized or exclude specific resources (CSS, Font, Image, JS) from specific optimization operations.

1. Navigate to the NitroPack settings page referenced above in the Custom Settings section.
2. Click Cache in the left sidebar
3. Scroll down to the Exclusions section
4. Click the toggle button to the right of Excluded resources or Excluded URLs to see the exclusion options
   

Excluded Resources

Specify the JavaScript, CSS, images, and font files you do not want to get optimized. Read more about excluded resources in the NitroPack article.

• Specify Asset URLs, Resource Types, Resource Relations, or Device types to exclude
• Select Excluded Operations (pictured above) to exclude from the selected resource types

Excluded URLs

Specify the pages you do not want to get optimized. Read more about excluded URLs in the NitroPack article.

• Specify full page URLs or URL patterns that you want to exclude
  • example URL: https://mynewsite.com/articles/article-1
  • example URL pattern: *articles/*

NitroPack Settings in the WordPress Admin Dashboard

Click NitroPack in the WordPress left sidebar to see available settings. For additional settings view the Custom Settings section above.

Some of the current noteworthy settings you can find here are:

Shortcodes exclusions
Load widgets, feeds, and any shortcode with AJAX to bypass the cache and always show the latest content.

Page optimization (Select what post/page types get optimized)
If you ever add a new custom post type, either through custom code or through a plugin that has custom post types, you should click the gear icon next to Page optimization to confirm that all relevant post types are selected to be optimized.

Copying to a different environment

In order to use NitroPack with a site utilizing multiple environments (Production, Staging, and Development) make sure to check the following requirements:

• NitroPack is enabled on all environments (no license is required for Staging and Development environments).
• NitroPack plugin is updated to the latest version on all environments.
• Ensure that the wp-content/cache folder is not purged after a push or pull to a different environment as NitroPack stores its configuration details in that folder. The folder name should be a string of numbers and letters and then “-nitropack”.
  ex: /wp-content/cache/1234abc-nitropack/.
• NitroPack plugin shows “connected” in the WordPress Admin dashboard on all environments.
  • If it’s connected You’ll see a green dot in the top bar menu like this:
    
  • If there are issues or the site is disconnected it will show either yellow or red dots.

Bypass NitroPack

If you are unsure that NitroPack is causing issues on the site, comparing the optimized page with its non-optimized version can help pinpoint optimization-related issues. 

• Bypass NitroPack’s cache by appending the ?nonitro parameter to a given URL (example: domain.com/page?nonitro)
• If the issue persists, this means it’s not related to NitroPack.

If needed, quickly release the NitroPack license in the User Portal by clicking the (…) dot icon on the right and selecting Release license.

Confirm NitroPack

If you are unsure if NitroPack is affecting an asset, this can be confirmed by the existence of the x-nitro-cache:HIT header.

Visit the page you have NitroPack enabled on and right-click, then click Inspect. You should then find the x-nitro-cache Response Header. It should have a value of HIT, indicating that NitroPack cache was present and served.

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Using GeoTarget with NitroPack

To make sure that NitroPack caches content dynamically based on GeoTarget values, you need to add dynamic content cookies within the NitroPack settings.

1. Go to the Products page in the User Portal
2. Click on NitroPack under Your products
3. Click the three dot button to the right of the environment you want to adjust
4. Click Settings
   
5. This will take you to the settings page inside of NitroPack. Click Cache in the left sidebar.
6. Scroll down to the Dynamic content cookies section
7. Add all of the NitroPack cookie names in the Cookie name field, that correspond to the GeoTarget values you use for your website. View the table below for the corresponding cookie names.
   
8. Cookie values (optional) – Cookie values can be added as a comma separated list. Specifying cookie values is not required, but it is highly recommended. Including all possible values ensures that the cache warmup feature can simulate each scenario and prepare optimizations in advance. If you decide to skip it, an organic visit must occur before our service can detect and optimize that combination. If you leave Cookie values empty, our service will create optimizations for all encountered combinations.
9. Groups (optional) – Grouping cookie names with a group number tells our service that a combination outside these groups cannot occur. This prevents unnecessary cache files from being created for different combinations to preserve server space.
   • An example might be preventing combinations of a country and a currency, by grouping a cookie for a specific language value with the cookie for a specific currency value.

Cookie Names for GeoTarget

NitroPack cookie name	GeoTarget value
nitro_geot_country_code	HTTP_GEOIP_COUNTRY_CODE
nitro_geot_country_code3	HTTP_GEOIP_COUNTRY_CODE3
nitro_geot_country_name	HTTP_GEOIP_COUNTRY_NAME
nitro_geot_latitude	HTTP_GEOIP_LATITUDE
nitro_geot_longitude	HTTP_GEOIP_LONGITUDE
nitro_geot_area_code	HTTP_GEOIP_AREA_CODE
nitro_geot_region	HTTP_GEOIP_REGION
nitro_geot_city	HTTP_GEOIP_CITY
nitro_geot_postal_code	HTTP_GEOIP_POSTAL_CODE

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Conflicts

Conflicts between NitroPack and other caching or optimization plugins may occur. As a result, visual issues or other issues may occur on the website.

In general, NitroPack can’t be used with other caching plugins that have any of the following features enabled:

• Page caching
• Image lazy loading
• CSS optimization
• JavaScript optimization

The overlapping functionalities can cause our optimization mechanism not to work at all.

Therefore, we don’t recommend using NitroPack simultaneously with another optimization plugin like (but not limited to):

• Autoptimize
• a3 Lazy Load
• Asset Cleaner Pro
• Breeze
• Comet Cache by WP Sharks
• Fast Velocity Minify
• Hummingbird
• JCH Optimize
• Jetpack Boost
• Litespeed Cache
• PageSpeed Ninja
• Perfmatters
• PhastPress
• Powerpack (WPTouchPro)
• SG Optimizer
• Smush (only their lazy load option must be disabled, not the entire plugin)
• Swift Performance
• W3 Total Cache
• WPML
• WP Fastest Cache
• WP Fastest Cache Premium
• WP Rocket
• WP Super Cache
• WP-Optimize (only their page caching must be disabled, not the entire plugin) 

Auto-detected conflicting WordPress plugins
NitroPack generally provides a warning when an incompatible plugin is detected. If you start using NitroPack you can remove conflicting plugins listed below.
Note: Sometimes disabling these plugins might not be enough and deleting them might be required to avoid conflicts.

• Asset CleanUp Pro – their cache might cause issues in some cases
• Autoptimize
• Breeze cache plugin by Cloudways
• Comet Cache by WP Sharks
• Hummingbird
• JetPack – Enable site accelerator feature under the Performance Tab must be disabled
• LiteSpeed Cache
• PageSpeed Ninja
• Pegasaas Accelerator WP
• PhastPress
• Smush by WPMU DEV
• Swift Performance
• W3 Total Cache
• WP Fastest Cache
• WP Optimize (only their page caching must be disabled, not the entire plugin)
• WP Super Cache
• WP-Rocket

Ad Management

• Ezoic for WordPress integrated via DNS is not compatible
  • Ezoic integrated via WordPress plugin is compatible

Cache conflicts
Page caching plugins must be disabled for NitroPack to handle caching.

• Asset Cleanup Pro
• Autoptimize
• Breeze
• Comet Cache by WP Sharks
• Ezoic Speed Accelerator
• Fast Velocity Minify
• Hummingbird
• JCH Optimize
  • Not a WordPress plugin: Google’s page speed optimization module has to be turned off
• Jetpack Boost
• Litespeed Cache
• PageSpeed Ninja
• Perfmatters
• PhastPress
• Powerpack (WPTouchPro)
• SG Optimizer
• Swift Performance
• Swift Performance
• W3 Total Cache
• WP Fastest Cache
• WP Fastest Cache Premium
• WP Rocket
• WP Super Cache
• WP-Optimize (only their page caching must be disabled, not the entire plugin)

Optimization
This is the only feature that can work alongside NitroPack.

• AMP – AMP pages do not get optimized as AMP is considered an already optimized format.

Images
NitroPack takes care of image optimization so the following plugins are no longer necessary.

• a3 Lazy Load
• BJ Lazy Loader – Could work only with “Lazy load images” and “Lazy load iframes” options turned off, but deactivating it is recommended.
• EWWW Image Optimizer – disable Lazy load, Easy IO, WebP Conversion
• imagify – Create webp versions of images
• JetPack – disable Lazy loader
• MediaAce – disable Lazy loader (They also lazyload iframes, YouTube, etc). You can disable just image lazyloading but other issues may surface.
• OptiMole – disable Lazy loader
• ShortPixel Adaptive Images (separate plugin)
• ShortPixel WebP conversion
• Smush – disable Lazy loader
• WebP Express
• WP Compress

Incompatible non-optimization plugins:

• Anti-spam by CleanTalk – disable “SpamFireWall” (Disabling only “anti-crawler” will not work)
• WP-Cron Control – must be deactivated
• Buddypress – not compatible with NitroPack
• Buddypress + BuddyBoss – not compatible with NitroPack. Pages have x-nitro-disabled-reason: 404 which is expected
• PublishPress Revisions

Exceptions

The NitroPack “Incompatible plugin” warning can be ignored for the following plugin, but please do the following:

• OptiMole – disable Lazy loader

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Limitations

Currently there are some caveats when using NitroPack. As we continue to modify and improve the plugin, these may change in the future.

• Sandbox Sites
  • NitroPack is not currently available for Sandbox Sites.
• Logged in admin users
  • NitroPack will not optimize the site for users logged in to WP-Admin. This can be tested by checking the following headers: X-Nitro-Disabled and X-Nitro-Disabled-Reason as they will show X-Nitro-Disabled: MISS and X-Nitro-Disabled-Reason: request type not allowed. NitroPack was not designed to improve or change the performance of the native WP admin options. Users logged in to the WP-Admin are uncached, and the X-Nitro-Disabled-Reason: logged in header confirms NitroPack is off during these tests.
• Multisite
  • NitroPack is not currently available for multisite configurations.
• Password Protection
  • Sites utilizing password protection cannot be fully optimized by NitroPack.
  • If the website’s password protection software supports whitelisting, Nitropack IPs should be allowed to ensure full optimization can occur. Learn more here.
    
    The IP addresses for NitroPack that you can add to your allow list are:
    178.62.81.205
    46.101.77.196
    178.62.71.222
    159.65.180.53
    34.89.113.53
    34.147.235.168
    35.246.2.61
    104.154.182.50
• WP Engine Headless Platform
  • NitroPack is not currently available for WP Engine Headless Platform plans.
• Environments
  • NitroPack is intended to be used on Production environments. Staging and Development environments won’t see the full performance improvements because those environments are primarily used for testing and not live traffic. Nevertheless, NitroPack should be enabled on all environments (Production, Staging and Development) to be able to push and pull changes between environments without interrupting NitroPack.
• Reverse Proxy
  • Due to the way reverse proxy configurations obfuscate traffic, NitroPack will not function.