Syntax-highlighting Code Block (with Server-side Rendering)


This plugin extends the Code block in WordPress core to add syntax highlighting which is rendered on the server. Pre-existing Code blocks on a site are automatically extended to include syntax highlighting. Doing server-side syntax highlighting eliminates the need to enqueue any JavaScript on the frontend (e.g. Highlight.js or Prism.js) and this ensures there is no flash of unhighlighted code (FOUC?). Reducing script on the frontend improves frontend performance and it also allows for the syntax highlighted code to appear properly in AMP pages as rendered by the official AMP plugin (see also ampproject/amp-wp#972) or when JavaScript is turned off in the browser.

In addition to not adding any JavaScript to the frontend, the stylesheets needed for styling the Code block will only be added to the page if there is a Code block present. The stylesheets are added inline when the Code block is rendered, ensuring that they do not block rendering of any content higher in the page. If stylesheets fail to load for any reason, the block simply renders without styling, with one key exception: highlighted lines are wrapped in mark elements so they’ll get highlighted regardless, including in RSS Feeds and posts syndicated in email (as long as the mark element is supported in the client).

This extended Code block uses language auto-detection to add syntax highlighting, but you can override the language in the block’s settings sidebar. (There is currently no syntax highlighting of the Code block in the editor.) The plugin supports all programming languages that highlight.php supports (being a port of highlight.js). The Code block also is extended to support specifying the aforementioned highlighted lines. There is also a checkbox for whether to show line numbers on the frontend (with the numbers being non-selectable). Lastly, given inconsistencies across themes as to whether lines in a Code block should be wrapped, this plugin adds styling to force them to no-wrap by default, with a checkbox to opt-in to wrapping when desired.

For advanced usage, please see the plugin wiki.

This plugin is developed on GitHub. See list of current issues with the plugin. Please feel free to file any additional issues or requests that you may come across. Pull requests are welcome.


This is a fork of Code Syntax Block by Marcus Kazmierczak (mkaz), which is also available on Copyright (c) 2018 Marcus Kazmierczak. Licensed under GPL 2.0 or later.

highlight.php is released under the BSD 3-Clause License. Copyright © 2006-2013, Ivan Sagalaev (, highlight.js (original author). Copyright © 2013, Geert Bergman (, highlight.php


  • Code blocks can be added as normal, optionally overriding the auto-detected language. Also specify any lines to be highlighted, whether to show line numbers, and if the lines should wrap.
  • The Code block renders with syntax highlighting on the frontend without any JavaScript enqueued. Stylesheets are added only when block is on the page.


12 de abril de 2021
Just saw this plugin in the source code of another developers blog. I use(d) another block to highlight my code but instantly bought in the idea of server render the code instead of ship JS to my users. I try to step up my game of resource efficient webdevelopment. So reduce the JS I ship to users - server rendering over client side rendering etc. So this plugin rocks. Also I am glad that changing over will be doable. The plugin I currently use let me switch to your plugin without trouble, so this will be a task for every now and then in the next days. Thanks for this plugin!
13 de marzo de 2021
Why this plugin is awesome. 1) The plugin renders on the server side which is ideally more work for your server. But with proper caching implementation, this approach increases page speed as the client doesn't have to load javascript on the client side. 2) The plugin adds on top of the existing gutenberg code block. Most of the syntax highlighters out there try to provide their own gutenberg block which makes it difficult to switch between plugins. For instance, I was using code syntax block plugin and I had to go to each post to convert them back to regular code blocks. 3) No client side scripts thus optimal for AMP enabled pages. As your AMP pages get cached on Google AMP cache anyway, your server has to generate pages rarely. 4) More theme options compared to other code block highlighters out there.
2 de enero de 2021
This plugin is the best syntax highlighting plugin that I have used, thanks for all the hard work in developing it. One recommendation though... I just stumbled upon the ability to change the color scheme in the Customizer. This is an awesome feature, but not one that is highlighted in the description of the plugin or in the screenshots. Of course it is mentioned in the Advanced Usage wiki, but I have been using the plugin for months and definitely overlooked that 😉. A brief mention in the main description and a screenshot of the different theme options would definitely help unobservant users like myself. Thanks again!
24 de octubre de 2020
I love that this is baked into the core code block without having to resort to a third-party integration that may or may not work. Well done on this one. Just a heads up though, which may require more testing. The latest Gutenberg release and this plugin do not appear to play well together. I had to disable the Gutenberg plugin, which invalidated the code blocks, and I had to recover each one. One feature request: Please add a rel attribute so I can display the language. Thanks again, Ronald Huereca
11 de octubre de 2020
This is a great plugin. 1. The code looks just like it does in Visual Studio (theme: vs2015) 2. It improves performance in two ways: -generates html on the server-side, instead of rendering on the client-side. This is the main reason i looked into getting a different syntax highlighting plugin. I use a caching plugin, so it annoyed me that it was doing pointless client-side rendering. -the generated html is 3x smaller than the other plugin i was using. So the payload is smaller, and it's simply less work for the browser to paint. 3. It's simple. You just built-in Code block and change the language after you paste. 4. It has line wrapping. My current plugin doesn't have this, so it puts scroll bars on the code (looks bad) Great job with this plugin!
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Registro de cambios

For the plugin’s changelog, please see the Releases page on GitHub.