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Jetpack Boost

Jetpack Boost is a WordPress plugin that provides one-click optimizations that supercharge your WordPress site’s performance and improve web vital scores for better SEO. Jetpack Boost’s Automated Critical CSS feature requires a paid subscription. You can learn more on our plans page.

What do I need to run Jetpack Boost on my site?

  • A web host that meets the WordPress host requirements.
  • The latest version of WordPress. If your version of WordPress is out of date, you’ll see a prompt to automatically upgrade with a single click, or you can upgrade manually.
  • A account is required for the upgraded Jetpack Boost plan (which includes our Automated Critical CSS feature). You do not need to have a account for free Jetpack Boost. Read more about Jetpack and the connection here.
  • A publicly accessible WordPress site: no password protection or Coming Soon / Maintenance Mode plugin in use.
  • A publicly accessible XML-RPC file.

Installing Jetpack Boost

Installing Jetpack Boost can be done from your site’s WP Admin. To install Jetpack Boost via WP Admin:

  1. Go to Plugins → Add New.
  2. Search for Jetpack Boost. The latest version will be in the search results and will be named Jetpack Boost – Website Speed, Performance and Critical CSS
  3. When you find the plugin, click Install Now.
  1. Once installed, click Activate
  2. After activating, you will be taken to a page where you can choose between the paid and free tiers.
  3. After selecting the plan, you will be redirected to the Jetpack Boost dashboard and your current scores for Mobile and Desktop will be calculated.
Jetpack Boost’s performance scores will show as a meter at the top of the page.
  1. You can turn on and off the different Jetpack Boost optimization options. Each time you turn an option on or off, click Refresh located in the top right corner of the screen.

Jetpack Boost Optimization Options

Jetpack Boost has a few different optimization options:

Optimize CSS Loading

This option moves important CSS styles to the start of the page’s code, which can help display your content faster. This is commonly referred to as Critical CSS. If you turn on this setting, Jetpack Boost will begin optimizing your site’s CSS. Important: You need to stay on this page until the CSS optimization is complete. If you don’t, the process will pause, and you will need to come back and complete it. Learn more about how to make the most of the optimize CSS feature.

Upgrade: If you opt to use the Optimize CSS Loading feature, you also have the option to upgrade Jetpack Boost’s Automated Critical CSS feature. This feature automatically regenerates your critical CSS after site changes, recalculates performance scores after each change, and you will receive dedicated email support.

Defer Non‑Essential JavaScript

This setting makes JavaScript that isn’t essential to the page working load once everything else has loaded.

Lazy Image Loading

This improves page loading speed by only loading images when the user reaches them on the page. Note: If you use Jetpack Boost with the Jetpack plugin, toggling Lazy Image Loading will toggle the Lazy Images feature in the Jetpack plugin as well.

Concatenate JS

Consolidates multiple JavaScript files into one comprehensive script and shrinks it for optimal use, subsequently reducing the number of server calls and enhancing the rate of webpage loading.

When enabled, an option to exclude specific JavaScript strings becomes accessible. Click on this option, enter the JavaScript scripts you wish to exclude in the provided field, and then click Save.

Enable Concatenate JS and exclude JS strings if necessarily 

Concatenate CSS

Combine multiple CSS files into a single, minified file. This optimizes website performance by reducing page load time and the number of server requests. When enabled, an option to exclude specific CSS strings becomes available. Click on this option, enter the CSS strings you wish to exclude in the provided field, and then click Save.

Enable Concatenate CSS and exclude CSS strings if necessarily 

Image CDN

Use Jetpack’s extensive Content Delivery Network to ensure rapid and reliable delivery of your images. This feature not only optimizes the size of your images, but also transforms them into the highly efficient WebP format, and leverages a global server network for their distribution.

Upgrade: Get control over your image quality, allowing you to choose the level of detail you prefer for your images, which will contribute to improving your site speed:

Upgrade to gain control over your images quality

Image Guide BETA

This feature provides details about image size on your site, so you can see which one can be adjusted to increase the site speed. This feature is explained in more detail here.

Image Size Analyzer BETA

Detects and assists in optimizing images that are not appropriately sized on your website, thereby enhancing loading times and increasing both user satisfaction and search engine rankings.

Upgrade: This feature is available with Jetpack Boost’s paid version or included in the Jetpack Complete plan. Learn more about how to analyze and optimize the images here.

Measuring the speed boost from WP Super Cache

If you use the WP Super Cache plugin on your site, you can measure the speed boost from WP Super Cache right from the Boost dashboard and see how much difference it makes for your users:

Find out how much difference WP Super Cache makes for your site visitors.

Boost Performance Issues in Site Health Status

If you check your site’s health via Tools > Site Health in your site’s WP Admin, you may see the following message:

Jetpack Boost detected the following performance issues with your site:

  • Outdated Critical CSS

This means your site’s HTML or CSS has changed since Critical CSS was last generated, and it needs to be refreshed. To fix that:

  1. Click the link below the message to visit the Boost settings page.
  2. Click the Regenerate button to regenerate your site’s critical CSS.

Alternatively you can upgrade to enable automatic CSS regeneration whenever changes are made.

Frequently Asked Questions

Do I need Jetpack for Jetpack Boost plugin to work?

Jetpack Boost is a part of the Jetpack brand, but it doesn’t require the Jetpack plugin to run. This is a separate plugin from Jetpack, and it will always remain that way.

Does it work on a multisite installation?

Yes. If you are using WordPress Multisite, Jetpack Boost must be installed and activated separately on each site in the network (on sites where Jetpack Boost connections are desired).

Any Administrator for that site can create the Jetpack Boost connection. It does not have to be a different Administrator user or a different user for each site.

I have a local WordPress install or a private site. Can I use Jetpack Boost?

Yes, “Offline Mode” now allows testing of Jetpack Boost on local environments easily.

Can I use Jetpack Boost in combination with other performance plugins?

Jetpack Boost and other optimization plugins may have similar optimization options available. Jetpack Boost options can be easily turned on and off, and other plugins will usually offer the same facility too.

We don’t recommend having the same optimization enabled in Jetpack Boost and other optimization plugins, as it is unlikely to benefit your site and may cause unexpected issues.

How do I install Jetpack Boost in my language?

Once you have installed WordPress in your own language, Jetpack Boost will automatically switch to your language, as long as a translation file is available. You can check for existing translations or help translate the plugin here.

How is Critical CSS generated?

This link explains a bit more about critical CSS generation. To add to that, hard-coded/inline CSS is not included in Critical CSS because it is already inline on the page.

Where is the Critical CSS stored?

The Critical CSS is stored in the database posts_table as a custom post type.

Is Critical CSS generated for mobile versions of my site?

We don’t generate specific CSS only for mobile, but we do take samples of the site with both wide and narrow screen sizes and then combine them so that the Critical CSS produced is valid for both mobile and desktop devices.

How do I exclude some JavaScript files from being deferred?

If you experience unwanted behavior when you defer JS with Boost, the affected functionality could rely on the JavaScript files being in a certain order or being made available to the page as soon as possible.

In such cases, you can tell Jetpack Boost not to defer those specific files by adding the attribute data-jetpack-boost="ignore" to the script tag.

E.g. <script data-jetpack-boost="ignore">.


How do I activate my Jetpack Boost license?

Please see the documentation on Activating Jetpack Boost via License Key.

I’m having trouble getting Jetpack Boost connected to How can I troubleshoot?

Please see the documentation on Jetpack connection issues as the connection flow between Jetpack and Jetpack Boost is similar.

Get Help

For free Jetpack Boost users, you can post a support request on the Jetpack Boost Plugin Support page. If you have purchased the Automated Critical CSS upgrade, you can contact support for more personalized assistance.

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  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 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: site ID, local site ID, and site URL. Additionally, for activity tracking (detailed below): IP address, user ID, username, 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.

Site Visitors


Activity Tracked
Site Owners / Users

We track when, by which user, and which website is connected to and when the plugin is deactivated. We also track activities such as the Critical CSS generation process, when, and which, configuration settings are modified.

Site Visitors


Data Synced (Read More)
Site Owners / Users


Site Visitors


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