Jetpack Boost helps your site load faster by optimizing how key assets are delivered—like CSS, JavaScript, and images. This guide explains how to install Boost, what each feature does, and how to use them.
You can get started for free, or upgrade to unlock premium features like automatic CSS optimization, image quality controls, and advanced image analysis.
WordPress.com hosting plans (Business or Commerce) don’t include premium Jetpack Boost features—you’ll need a Paid Boost plan to use them.
Installation Requirements
To use Jetpack Boost, make sure your site:
- Runs the latest version of WordPress.
- Is publicly accessible (not behind a password or maintenance mode).
- Meets WordPress hosting requirements.
- Has a publicly accessible xmlrpc.php file.
You don’t need the Jetpack plugin to use Boost. Jetpack Boost is a separate plugin.
Install Jetpack Boost
- From WP Admin → Plugins → Add New, search for Jetpack Boost.
- Click Install Now, then Activate.
- Choose a Free or Paid plan.
- After activation, you’ll be redirected to the Boost dashboard, where your Mobile and Desktop performance scores will be calculated.
If Jetpack Boost can’t connect to your site, follow these troubleshooting steps.
Jetpack Boost Dashboard
Once installed, the dashboard displays:
- Mobile and Desktop performance scores based on Lighthouse.
- A performance letter grade.
- Toggle switches to enable or disable features.
- A Refresh button to update scores after changes.
- A historical score graph (available on paid plans).
Feature Reference
Jetpack Boost includes several tools to help improve your site’s front-end performance. Each one can be toggled individually from the dashboard.
| Feature | Free | Paid |
|---|---|---|
| Site performance scores View site performance scores based on Google PageSpeed Insights. Learn more. | ✅ | ✅ |
| Optimize CSS Loading Regenerate CSS manually after making design changes. | ✅ | ✅ |
| Cache site pages Creates static versions of your pages to reduce load time for visitors. | ✅ | ✅ |
| Defer non‑essential JavaScript Delays the loading of scripts that aren’t required for initial rendering, helping your content appear faster | ✅ | ✅ |
| Image performance guide Calculate recommended dimensions for images on your site. Learn more. | ✅ | ✅ |
| Image CDN Delivers your images from Jetpack’s high-speed global CDN. | ✅ | ✅ |
| Concatenate JS and CSS Combines multiple JavaScript or CSS files into one to improve load performance. | ✅ | ✅ |
| Automated Critical CSS Optimizes CSS loading automatically after changes. | ❌ | ✅ |
| Performance history Track your performance history over time. | ❌ | ✅ |
| Image quality control Adds image quality controls to CDN-served images and access to lazy load resizing. | ❌ | ✅ |
| Cornerstone Pages Optimizes the Largest Contentful Paint (LCP) image on your Cornerstone Pages to improve perceived load time and Core Web Vitals scores. | One (1) page | Ten (10) pages |
Cornerstone Pages
Cornerstone Pages help Boost prioritize performance improvements on your most important content. Boost focuses on these pages when generating Critical CSS and Page Speed scores. Your homepage will always be considered a Cornerstone Page.
- On the Free plan, you can set one additional Cornerstone Page.
- On the Paid plan, you can set up to ten additional pages.
By default, Boost adds:
- Your WooCommerce shop page (if active).
- Pages marked as Cornerstone Content in the Yoast SEO plugin.
Note: If you’re on a Free plan, only one page from the above (not counting home page) will be added when you first install Jetpack Boost.
You can view or change this list from the Boost dashboard, right below your speed scores.
Boost stores Cornerstone Pages as relative URLs, so if you change domains, your list will continue working without updating anything.
Cornerstone Pages affect:
- Speed scores: Boost uses the first page in the list to measure performance.
- Critical CSS: Each Cornerstone Page gets its own optimized CSS, improving loading precision.
Prerender Cornerstone Pages
When enabled, this feature uses WordPress 6.8’s speculative loading to prerender Cornerstone Pages in supported browsers. This means linked pages may begin loading in the background when users hover over them, resulting in faster perceived performance when they click.
You can toggle this on or off from the Cornerstone Pages section in the Boost dashboard. It’s off by default.
Learn more about Cornerstone Pages.
Optimize CSS Loading
It moves essential styles—called Critical CSS—to the top of your page’s code so that content starts rendering faster.
- On the Free plan, you may need to regenerate CSS manually after making design changes.
- On the Paid plan, this happens automatically after changes.
If your Site Health tool reports “Outdated Critical CSS,” click the link to visit the Boost dashboard and click Regenerate.
Stay on the dashboard while Boost generates Critical CSS. If you navigate away, the process will pause.
Learn more about optimizing CSS.
Cache Site Pages
Creates static versions of your pages to reduce load time for visitors.
- Automatically updates the cache when content changes.
- Includes an option to exclude specific pages from caching (helpful for frequently updated content).
To enable:
- Toggle Cache Site Pages in your dashboard.
- (Optional) Click to exclude pages from caching using URL patterns.
If this setting isn’t available, your host or another plugin may already provide server-side caching.
Learn more about caching site pages with Boost.
Defer Non-Essential JavaScript
It delays the loading of scripts that aren’t required for initial rendering, helping your content appear faster.
To enable it, toggle Defer Non-Essential JavaScript in the dashboard.
If site features break (e.g., forms or sliders), they may depend on JavaScript, which needs to load earlier.
Here is what you can try:
- Turn the setting off.
- Or exclude specific scripts using the script handle.
Concatenate JavaScript
It combines multiple JavaScript files into one, minimizing the number of requests your browser needs to make.
To enable it, toggle Concatenate JS in your Boost settings.
Excluding specific scripts
Some JavaScript files may not function correctly when combined. To exclude them you can identify the script’s handle by checking your page’s source code or plugin documentation.
Example script tag:https://yourjetpack.blog/wp-content/plugins/snow-effects/snow-effects.js
- The handle is:
snow-effects. - Add
snow-effectsto the Excluded Files field.
When successful, you’ll see a comment like this in the page source:
<!-- No Concat JS snow-effects => Excluded option -->
This feature works only with scripts added via the WordPress Enqueue API. It doesn’t affect inline or embedded scripts.
Concatenate CSS
Combines multiple CSS files into one to improve load performance.
To enable it, toggle Concatenate CSS in your Boost dashboard.
Excluding specific stylesheets
Some stylesheets may break when combined. To exclude them, you can find the stylesheet’s handle from the id attribute in the HTML.
Example:<link rel="stylesheet" href="https://example.com/wp-content/themes/twentytwenty/style.css" id="twentytwenty-style-css">
- The handle is:
twentytwenty-style. - Add
twentytwenty-styleto the Excluded Files field.
Like JS concatenation, this works only with styles added using the WordPress Enqueue API.
Image CDN
Delivers your images from Jetpack’s high-speed global CDN. This also converts images to more efficient formats like WebP for faster loading.
- Free plan: Images are optimized and served via the CDN automatically.
- Paid plan: Adds image quality controls and access to lazy load resizing.
Adjusting image quality (Paid feature)
In the dashboard, you’ll see sliders for:
- JPEG
- PNG
- WebP
You can control each format’s quality level (0–100).
Auto-Resize Lazy Images (Paid feature)
Resizes lazily loaded images so they better match the size of their container. This helps reduce layout shifts and improves Cumulative Layout Shift (CLS).
- Available when Image CDN is enabled.
- Toggle Auto-Resize Lazy Images to turn this on.
LCP Image Optimization (Free for 1 page, Paid for up to 10)
Optimizes the Largest Contentful Paint (LCP) image on your Cornerstone Pages to improve perceived load time and Core Web Vitals scores.
Free plan: Optimizes one Cornerstone Page.
Paid plan: Optimizes up to ten.
Automatically identifies the largest visible image or background image and:
- Prioritizes loading with
fetchpriority="high" - Disables lazy loading for LCP images
- Uses Jetpack CDN and responsive image techniques
- Preloads background images with
image-set()
Learn more about LCP Image Optimization
Image Performance Guide
This tool walks you through identifying and resolving common image-related performance issues on your site.
This is especially useful if you’re unsure where to begin with image optimization.
Multisite and Local Usage
- Multisite installations: Activate Boost separately on each site in the network.
- Local environments: Use Offline Mode to test Boost on private or local sites.
Jetpack Boost Troubleshooting Hub
If Jetpack Boost isn’t working as expected, we have helpful documentation to get things back on track. Most issues can be fixed with a few simple steps—starting with the right diagnosis.
Use the guide below to find common issues, organized by feature. Each link opens a dedicated troubleshooting article with detailed instructions.
| Caching | Fix problems with Boost’s page caching—like file access issues or conflicts with other plugins. | Troubleshooting Jetpack Boost caching issues |
| Critical CSS | Solve errors related to outdated or missing Critical CSS. | Troubleshooting Critical CSS in Jetpack Boost |
| Concatenate CSS/JS | Fix layout or script errors caused by CSS or JavaScript concatenation. | Troubleshooting Concatenated CSS or JavaScript Delivery Methods |
| JavaScript Deferral | Learn how to exclude scripts that break when loaded late. | Exclude JavaScript files from Jetpack Boost deferral |
| Speed Score Measurement | Understand how Boost calculates speed scores and what each metric means. | How the speed score is measured with Jetpack Boost |
| Console Errors | Troubleshoot JavaScript or CSS errors reported in your browser’s console. | Understand Console Errors in Jetpack Boost |
| Cache Filter Customization | For developers: customize how Boost handles caching using optional filters and config files. | Using Filters to Customize Cache Parameters in Jetpack Boost |
| Speed Score Fluctuations | Understand why your Boost performance score may change on each refresh, and how to test more reliably. | Why my Jetpack Boost speed score changes (and what to do about it) |
| LCP Image Optimization | Fix issues preventing Boost from optimizing your Largest Contentful Paint images. | Troubleshooting common issues with Optimize LCP Images within Jetpack Boost |
Need help?
If you’re having trouble setting up or using Jetpack Boost, contact Jetpack Support. We’re happy to help.
Privacy Information
We are fully committed to the privacy and security of our customers and their personal data. For a better understanding of how Jetpack Boost uses your data, please refer to the Automattic Privacy Notice (Automattic owns and operates the Jetpack Boost plugin), the Automattic Privacy Policy, and the following section.
Jetpack Boost uses Jetpack libraries to connect to WordPress.com and calculate the page speed score (making use of the tk_ai cookie). There is more information about cookies within Jetpack here.
| Data Used | |
|---|---|
| Site Owners / Users
In order to calculate Page speed scores, generate Critical CSS blocks, etc, the following information is used: WordPress.com-connected site ID, local site ID, and site URL. Additionally, for activity tracking (detailed below): IP address, WordPress.com user ID, WordPress.com username, WordPress.com-connected site ID and URL, Jetpack version, user agent, visiting URL, referring URL, timestamp of event, browser language, country code, Critical CSS generation URL, block counts, block sizes, error details, generation time, provider keys, Boost version, and active Boost features. We monitor the types of errors encountered during the Boost Cache setup process to pinpoint user challenges and direct our enhancement efforts. |
Site Visitors
None. |
| Activity Tracked | |
| Site Owners / Users
We track when, by which user, and which website is connected to WordPress.com and when the plugin is deactivated. We also track activities such as the Critical CSS generation process, when, and which, configuration settings are modified. For Jetpack Boost Premium subscribers, we also track site performance over time. We use this data to populate the Historical Performance section of the Jetpack Boost dashboard. We track activities such as toggling the Cache feature and altering its settings. We use this data to identify common usage patterns to better target our future improvements. |
Site Visitors
None. |
| Data Synced (Read More) | |
| Site Owners / Users
We sync options that identify whether or not optimization features are enabled, latest speed score measurements, and options that contain the state of last critical CSS generation. |
Site Visitors
None. |
Jetpack 