Jetpack Boost – Website Speed, Performance and Critical CSS


Speed up your WordPress site by optimizing page performance with Jetpack Boost. Easily activate one-click optimizations to boost your Core Web Vitals.

Did you know that a faster website:-

  • Ranks higher on Google.
  • Improves bounce rate (people stay on your site for longer).
  • Increases your conversion rate.

Increase your website performance and speed up your website with one-click optimizations that supercharge your WordPress site’s performance and improve core web vitals scores for better search engine listings.

Improving Core Web Vitals helps you rank higher on Google. A faster website also improves your SEO, helps you reduce your bounce rate and increase your ecommerce conversion rate.

  • Largest Contentful Paint (LCP): Measures loading performance. Improve your LCP and improve your website loading speed.
  • First Input Delay (FID): Measures interactivity. To improve user experience pages should have a low FID.
  • Cumulative Layout Shift (CLS): Measures visual stability. Lowering your CLS helps improve your user experience.

Performance Modules

Optimize your website with the same techniques used on the world’s most successful websites.

Each technique that is used to increase website performance is packaged up as a module that you can activate and try out.

Currently, the plugin has 3 performance modules available:

  1. Optimize CSS Loading generates Critical CSS for your homepage, posts and pages. This can allow your content to show up on the screen much faster, particularly for viewers using mobile devices.

    Read more about critical CSS generation at

  2. Defer Non-Essential Javascript moves some tasks to after the page loads, so that important visual information can be seen sooner and your website loads quicker.

    Read more about deferring javascript at

  3. Lazy Image Loading only loads the images the user can see. As the user scrolls, images are loaded just before they show up on the page. This simple optimization makes websites faster and saves bandwidth for your host and your customers.

    Read more about lazy image loading at

    Google PageSpeed API is used to measure the performance score of a site. It’s important to look at the Page Speed score because Core Web Vitals are going to be used as a ranking factor in search engines which means improving your SERP listing and increase your website visitors.

Don’t want to have to manually generate your critical CSS each time you update your site? Let us do the heavy lifting for you with automated critical CSS – each time you update your site we will automatically regenerate your critical CSS and update your performance scores. Upgrading also gives you dedicated email support access.

With 💚 by Jetpack

This is just the start!

We are working hard to bring more features and improvements to Jetpack Boost. Let us know your thoughts and ideas!

We’d also like to give a special THANK YOU to the XWP team who provided help with initial research and scoping of the plugin and were engaged with our team throughout the project.


  • Jetpack Boost Critical CSS Generation
  • Jetpack Boost Speed Improvement


  1. Install Jetpack Boost via the plugin directory, and activate it.
  2. Activate Jetpack Connection
  3. Turn on performance modules one by one and observe how the performance score changes


What does Jetpack Boost do to help speed up my WordPress site?

Jetpack Boost makes small changes to the way that data is sent from your WordPress site to your users’ browser, to enable the browser to display your site faster.

Jetpack Boost includes a few separate features which can be turned on individually to improve your site’s performance. These include:

  • Optimize CSS Loading: This feature determines the most important CSS that your site needs to display your site’s initial content as quickly as possible, and embeds it directly into your site header.
  • Defer Non-Essential JavaScript: This feature forces all of the JavaScript which is not deemed essential to displaying your site to load after your site’s main content has been loaded.
  • Lazy Image Loading: This feature delays loading images on your site until they are scrolled into view, allowing the browser to load the first content that the user will see first.

What speed improvements can I expect when using Jetpack Boost?

Website Performance is complicated and can be affected by a number of factors. As a result, it is difficult to accurately predict how much impact it will have on each site.

Generally, the lower your speed score is to begin with, the more Jetpack Boost may impact your performance. We have seen user reports of up to 25 Speed Score points improvement simply by installing and using Jetpack Boost.

However, as performance can be impacted by so many factors, it is also possible for Jetpack Boost to have a small negative performance impact in some rare cases.

We recommend that you install Jetpack Boost, and try it for yourself. It includes a tool for measuring your Speed Score, to check what impact it has on your site.

Can I also defer non-essential CSS with Jetpack Boost?

Jetpack Boost automatically defers non-essential CSS if its “Optimize CSS Loading” feature is enabled.

The “Optimize CSS Loading” feature identifies the most important CSS rules your site needs to display your pages as quickly as possible (commonly called “Critical CSS”), and defers all other CSS rules from loading until your main content has loaded.

What are Web Vitals?

Web Vitals are the measurements that Google uses to better understand the user experience on a website. By improving Web Vitals scores you’re also improving the user experience on your site.

You can read more about Web Vitals on

How does Jetpack Boost plugin improve Core Web Vitals?

Each Core Web Vital relates to an aspect of how quickly your site can load and appear on new visitors’ screens.

Jetpack Boost makes small changes to the way that data is sent from your WordPress site to your users’ browsers, to enable your content to load faster. As a result, it can improve your Core Web Vitals scores.

For example, our “Optimize CSS Loading” feature ensures the most important CSS rules are sent to users’ browsers as early as possible, improving both First Contentful Paint (FCP) and Cumulative Layout Shift (CLS) scores.

Does this plugin require Jetpack?

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

Will this plugin be able to improve performance on any website?

This plugin includes a range of performance improvements, which can help almost any WordPress site perform better.

However, if your site is already extremely well optimized, Jetpack Boost may not have much room to improve it.

Jetpack Boost includes a tool for measuring your site’s Speed Score – we encourage users to try it out and see what impact it can have for them.

How do I know if it’s working?

Every site is different and so performance benefits for each module may vary from site to site. That’s why we recommend that you measure the performance improvements on your site by enabling the performance modules one by one. There are many tools out there that you can use for free to measure performance improvements:

Google PageSpeed measurements are built-in the Jetpack Boost dashboard.

Is Speed Optimization with Jetpack Boost safe?

Yes, it’s safe to try Jetpack Boost on any WordPress site.

Jetpack Boost does not alter your site’s content, it only modifies the way the content is sent to the user’s browser to allow it to display faster.

その結果、他のプラグインとの互換性がない場合、Jetpack Boost のすべての機能を安全にオフにすることができます。

How does Jetpack Boost compare with other speed optimization plugins?

WordPress の速度最適化プラグインは、ユーザーにとって複雑で不透明な場合があります。 多くの場合、説明の少ないチェックボックスの列があり、ユーザーが行った各変更や選択の影響を測定するツールは含まれていません。

Jetpack Boost は使いやすさに焦点を当てています。表示速度測定機能も搭載されており、選択した内容の影響をすぐに測定できます。

Does it work with static page cache?

Absolutely! If you have plugins like WP Super Cache or W3 Total Cache installed – Jetpack Boost is only going to help increase the performance benefits! Keep in mind that you need to wait for the cache to clear for Jetpack Boost improvements to show up.

Can Jetpack Boost make my website load faster if I have a large database?

現在 Jetpack Boost は大規模なデータベースの最適化には対応していません。 ただし、皆様のパフォーマンスを向上させるための新しい方法を常に探っていますので、今後も楽しみにしていてください。

Does Jetpack Boost help with image optimization?

大きな画像のあるサイトのパフォーマンスについては、Jetpack Boost の遅延読み込み機能で向上させることができます。遅延読み込みとは、スクロールして表示されるまで画像を読み込ませない機能のことです。

ただし、現在画像フォーマットの最適化機能はありません。 私たちはプラグインを改善する方法を常に探しています。これから搭載される新しい機能を楽しみにしていてください。

Is Jetpack Boost compatible with other caching and speed optimization plugins?

一部の例外を除き、Jetpack Boost はキャッシュプラグインや速度最適化プラグインと一緒に実行しても問題はありません。 ただし、ガイドラインとして、複数の最適化プラグインで同じ機能を有効にすることはお勧めしません。

たとえば、2つのプラグインが必須ではない JavaScript を延期しようとすると、それらが互いに競合し、サイトでの表示の問題が発生する可能性があります。

互換性の問題が発生した場合は、お知らせください。 Jetpack Boost サポートフォーラムにいつでもご連絡ください。


I highly recommend the Jetpack Boost plug-in and Jetpack overall for customer service.
Improving speed of desktop is great but for mobiles improving is needed


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1.7.0 – 2023-01-17


  • New Feature: Jetpack Boost Image Guide.
  • General: Add a notification bubble next to Boost in the WP-admin sidebar.
  • General: Added new tracks events.
  • User Experience: Add redirect to Boost dashboard after activating Boost plugin.


  • Admin notices: only display regeneration notice to admins.
  • Compatibility: Improve critical CSS compatibility with older Safari browsers.
  • General: Don’t let analytics failures prevent features from functioning.
  • Critical CSS: Fixed an issue where notices to regenerate critical CSS were showing unnecessarily.
  • General: Fix woocommerce deprecation warning.

See the previous changelogs here