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.


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 6 performance modules available:

  1. CSS 載入最佳化會為網站首頁、文章及頁面產生關鍵 CSS。這能讓網站文章在裝置螢幕上顯示更加快速,尤其對使行動裝置的使用者來說,效果更加顯著。

    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

  4. Image Guide is a must-have feature for anyone who wants to optimize the images on their website. With this guide, you can ensure that the images on your site are the right size and dimensions, which is critical for improving user experience, page speed, and site ranking. Following the tips and best practices outlined in the guide, you can reduce image file sizes and speed up your site. Check out our support page to learn more about this feature and how it can help you achieve a faster and smoother website experience for your users.

  5. Image CDN allows your site to serve automatically-resized images in modern web formats directly from Jetpack’s worldwide Content Delivery Network.

    Read more about Image CDNs at

  6. Concatenate and Minify CSS and JS combines and shrinks your JavaScript and CSS resources to reduce the number and size of requests to your server, ensuring your content loads faster.

    Read more about minifying files at

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.

Jetpack 團隊全心 💚 開發


開發團隊目前致力於將更多功能及改進加入 Jetpack Boost 中,請讓我們了解你的想法及意見。

我們也特別感謝 XWP 團隊,他們協助了外掛初期開發研究及外掛的範圍界定,並持續在專案中與我們保持合作。


  • Jetpack Boost Critical CSS Generation
  • Jetpack Boost Speed Improvement


  1. 透過外掛目錄安裝 Jetpack Boost,安裝完畢後請啟用外掛。
  2. 啟用 Jetpack 連線。
  3. 逐一開啟各個效能模組,並觀察他們對效能分數的影響。


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 growing number of 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.
  • Image CDN: This feature automatically resizes images to a more appropriate size for your visitors’ screens, converts them to modern image formats, and serves them from Jetpack’s worldwide network of servers.
  • Concatenate JS: This feature reduces the size of your JavaScript resources, and automatically combines them into fewer files, allowing your site to load faster with fewer requests.
  • Concatenate CSS: As with concatenating JavaScript, this feature shrinks your CSS files and allows them to load with fewer requests.

使用 Jetpack Boost 可以改進哪些網站項目的速度?

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.

Jetpack Boost 是否也能延遲載入非必要 CSS?

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.


「網站使用體驗」是 Google 讓使用者更容易了解網站使用者體驗的測量方式。要改善「網站使用體驗」,網站管理員也要改善網站的使用者體驗。

You can read more about Web Vitals on

Jetpack Boost 如何改善「網站使用體驗」?

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.

使用這個外掛需要搭配 Jetpack 使用嗎?

Jetpack Boost 是 Jetpack 品牌旗下的一項服務,但它不需要 Jetpack 外掛便可獨立執行。這是一個 Jetpack 品牌的獨立外掛,並且會以這種方式持續提供服務。


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.



Jetpack Boost 控制台已內建 Google PageSpeed 測量方式。

Jetpack Boost 的速度最佳化功能是否安全?

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.

As a result, all of Jetpack Boost’s features can safely be turned off in the event of an incompatibility with your other plugins.

Jetpack Boost 與其他速度最佳化外掛比較起來如何?

Speed Optimization plugins for WordPress can be complicated and opaque for users. They often offer columns of checkboxes with little explanation, and don’t include tools to measure the impact of each change or choice users make.

Jetpack Boost aims to be as easy to use as possible, and includes a Speed Score indicator to help users immediately measure the impact of their choices.


當然可以!如果網站已安裝如 WP Super Cache 或 W3 Total Cache 等外掛,Jetpack Boost 僅會協助增加網站效能。請注意,必須在清除快取後,才會看到 Jetpack Boost 的效能改善。

如果網站資料庫龐大,Jetpack Boost 能讓網站較快載入嗎?

Jetpack Boost does not include any optimizations that target large databases at this time. However, watch this space – we are always looking for new ways to help our users perform better.

Jetpack Boost 是否能處理圖片最佳化?

Jetpack Boost can help sites with large images perform better through lazy-loading, preventing images from loading until they are scrolled into view.

Additionally, its Image CDN feature automatically converts your images to more modern web formats, resulting in smaller image file sizes without a loss in quality.

Jetpack Boost 是否相容於其他快取及速度最佳化外掛?

With few exceptions, Jetpack Boost has no problems running alongside most caching and speed optimization plugins. As a guideline, we don’t recommend enabling the same feature in multiple optimization plugins.

For example, if two plugins attempt to defer your non-essential JavaScripts, then they may end up conflicting with each other and cause display problems on your site.

If you run into compatibility issues, please do let us know. You can drop us a line on the Jetpack Boost Support Forums at any time.


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〈Jetpack Boost – Website Speed, Performance and Critical CSS〉外掛目前已有 16 個本地化語言版本。 感謝全部譯者為這個外掛做出的貢獻。

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1.9.1 – 2023-05-31


  • New Feature: Added JS and CSS file minification


  • General: Improved the way modules are toggled internally
  • General: Updated package dependencies
  • Image CDN: Improved Image CDN description
  • User Experience: Removed back button from purchase success page


  • Cloud CSS: Don’t run local regenerate automagically when using cloud css
  • Cloud CSS: Fixed a mismatch in cloud-css key
  • Critical CSS: Fixed Critical CSS from making redundant requests on page load
  • Deferred JS: Fixed some extremely short pages (such as WooCommerce Box Office tickets being printed) from resulting in a blank page
  • General: Fixed some PHP 8.2 Warnings
  • User Experience: Fixed some language choices around Boost popups

See the previous changelogs here