This guide covers Link Rel: compression-dictionary (Emerging Feature). A supporting browser may download a compression dictionary that the server can use to send related future resources more efficiently.
Not every new browser feature is ready for every site. It helps to understand the problem first, then check whether the feature is mature enough before you depend on it.
How it is intended to work
A supporting browser may download a compression dictionary that the server can use to send related future resources more efficiently.
Code example
<head>
<link rel="compression-dictionary" href="/assets/site-dictionary.dict">
<title>Dictionary transport example</title>
</head>What you should notice
The feature is experimental and requires server support for compression dictionary transport; Content Security Policy may need to allow the dictionary URL. The link does not automatically compress every download.
Read the exact attribute and value shown in the code. That is the feature being demonstrated; the surrounding document merely provides the context required for valid HTML. Where JavaScript or CSS is involved, the complete working effect may need more than the markup shown.
How to test compatibility
- Create a plain HTML page with working essential content.
- Add the experimental feature as an enhancement, not as the only way to reach important information.
- Test in the latest browsers relevant to your audience, including keyboard and mobile use.
- Turn the feature off or use an older browser to confirm the fallback remains useful.
Common Beginner Mistakes
- The feature is experimental and requires server support for compression dictionary transport; Content Security Policy may need to allow the dictionary URL. The link does not automatically compress every download.
- Assuming a feature supported in a technical preview works for every visitor.
- Removing native accessible behavior before the replacement is proven.
Key Takeaways
- A supporting browser may download a compression dictionary that the server can use to send related future resources more efficiently.
- The feature is experimental and requires server support for compression dictionary transport; Content Security Policy may need to allow the dictionary URL. The link does not automatically compress every download.
- Keep a safe baseline and make new browser capabilities optional whenever possible.