--- title: Vercel CDN Compression product: vercel url: /docs/how-vercel-cdn-works/compression canonical_url: "https://vercel.com/docs/how-vercel-cdn-works/compression" last_updated: 2026-03-05 type: conceptual prerequisites: - /docs/how-vercel-cdn-works related: - /docs/image-optimization summary: Vercel helps reduce data transfer and improve performance by supporting both Gzip and Brotli compression install_vercel_plugin: npx plugins add vercel/vercel-plugin --- # Vercel CDN Compression Vercel helps reduce data transfer and improve performance by supporting both Gzip and Brotli compression. These algorithms are widely used to compress files, such as HTML, CSS, and JavaScript, to reduce their size and improve performance. ## Related pages > **For AI agents:** Follow these links to understand how this page connects to the rest of the Vercel ecosystem. For the full cross-link map (inbound, outbound, prerequisites, and semantic neighbors), see the .graph.md link below. - [Using Vercel as a Standalone CDN](https://vercel.com/kb/guide/using_vercel_as_a_cdn?from=related) — Use Vercel's external rewrites to proxy and cache content from external websites or APIs through Vercel's global edge ne - [What are the best practices for hosting videos on Vercel?](https://vercel.com/kb/guide/best-practices-for-hosting-videos-on-vercel-nextjs-mp4-gif?from=related) — Learn the ideal solutions for using video files like .mp4 and .gif on Vercel to prevent excess bandwidth consumption. - [Overview](https://vercel.com/docs/cdn?from=related) — Vercel's CDN is a globally distributed platform that handles routing, caching, security, and compression for every deplo - [Security](https://vercel.com/docs/cdn-security?from=related) — Learn how Vercel's CDN secures every request with HTTPS, TLS, DDoS mitigation, firewall protection, and security headers - [Encryption & TLS](https://vercel.com/docs/cdn-security/encryption?from=related) — Learn how Vercel encrypts data in transit and at rest. - [Pricing & Usage](https://vercel.com/docs/manage-cdn-usage?from=related) — Understand CDN pricing resources, monitor usage from your dashboard, and optimize Fast Data Transfer, Fast Origin Transf - [Caching](https://vercel.com/docs/caching?from=related) — Learn how Vercel caches content across multiple layers to deliver fast responses and reduce load on your backend. Full cross-link map for this page: [/docs/how-vercel-cdn-works/compression.graph.md](/docs/how-vercel-cdn-works/compression.graph.md) ## Compression algorithms While `gzip` has been around for quite some time, `brotli` is a newer compression algorithm built by Google that best serves text compression. If your client supports [brotli](https://en.wikipedia.org/wiki/Brotli), it takes precedence over [gzip](https://en.wikipedia.org/wiki/LZ77_and_LZ78#LZ77) because: - `brotli` compressed JavaScript files are 14% smaller than `gzip` - HTML files are 21% smaller than `gzip` - CSS files are 17% smaller than `gzip` `brotli` has an advantage over `gzip` since it uses a dictionary of common keywords on both the client and server-side, which gives a better compression ratio. ## Compression negotiation Many clients (e.g., browsers like Chrome, Firefox, and Safari) include the `Accept-Encoding` [request header](https://developer.mozilla.org/docs/Web/HTTP/Headers/Accept-Encoding) by default. This automatically enables compression for Vercel's CDN. You can verify if a response was compressed by checking the `Content-Encoding` [response header](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Content-Encoding) has a value of `gzip` or `brotli`. ### Clients that don't use `Accept-Encoding` The following clients may not include the `Accept-Encoding` header by default: - Custom applications, such as Python scripts, Node.js servers, or other software that can send HTTP requests to your deployment - HTTP libraries, such as [`http`](https://nodejs.org/api/http.html) in Node.js, and networking tools, like `curl` or `wget` - Older browsers. Check [MDN's browser compatibility list](https://developer.mozilla.org/docs/Web/HTTP/Headers/Accept-Encoding#browser_compatibility) to see if your client supports `Accept-Encoding` by default - Bots and crawlers sometimes don't specify `Accept-Encoding` in their headers by default when visiting your deployment When writing a client that doesn't run in a browser, for example a CLI, you will need to set the `Accept-Encoding` request header in your client code to opt into compression. ### Automatically compressed MIME types When the `Accept-Encoding` request header is present, only the following list of MIME types will be automatically compressed. #### Application types - `json` - `x-web-app-manifest+json` - `geo+json` - `manifest+json` - `ld+json` - `atom+xml` - `rss+xml` - `xhtml+xml` - `xml` - `rdf+xml` - `javascript` - `tar` - `vnd.ms-fontobject` - `wasm` #### Font types - `otf` - `ttf` #### Image types - `svg+xml` - `bmp` - `x-icon` #### Text types - `cache-manifest` - `css` - `csv` - `dns` - `javascript` - `plain` - `markdown` - `vcard` - `calendar` - `vnd.rim.location.xloc` - `vtt` - `x-component` - `x-cross-domain-policy` ### Compression allowlist The compression allowlist above is necessary to avoid accidentally increasing the size of non-compressible files, which can negatively impact performance. For example, most image formats are already compressed such as JPEG, PNG, WebP, etc. If you want to compress an image even further, consider lowering the quality using [Vercel Image Optimization](/docs/image-optimization). --- [View full sitemap](/docs/sitemap)