Brotli encoding
Sends an Accept-Encoding: br request and confirms the response is Brotli compressed - the format that ships ~15% smaller than gzip on text.
Content Compression Checker
Sends two requests - one accepting br/gzip, one accepting identity - to detect Gzip, Brotli, or zstd compression and compute the size savings. Also verifies the Vary: Accept-Encoding header.
Instant audit. No account required.
What the Content Compression audit checks
Three checks, one verdict. Each tile is a primitive your AI agent can read alongside the full JSON payload.
Gzip fallback
Falls back to gzip detection so older clients and proxies still get the bandwidth savings rather than identity bytes on the wire.
Vary header
Verifies the server emits Vary: Accept-Encoding so a shared cache cannot accidentally hand the compressed body to a client that asked for identity.
UpMonitor's Compression Checker verifies if your server is correctly using Gzip or Brotli compression to deliver assets. By compressing text-based files (HTML, CSS, JS), you can reduce bandwidth usage by up to 80% and significantly improve page load speeds. Free to use - no signup required.
Audit your server's compression settings instantly to ensure your site is as fast as possible.
ℹ️
HTTP Compression is a capability that can be built into web servers and web browsers to better utilize available bandwidth, and provide greater transmission speed between both. The most common methods are Gzip and the more modern Brotli.
What Our Compression Checker Validates
Our free performance tool audits your server's response headers:
✅ Brotli Support Check
Checks for the br content-encoding. Brotli is the modern standard for compression, offering better ratios than Gzip for most web assets.
✅ Gzip Support Check
Verifies that Gzip (gzip) is enabled as a fallback for older browsers. Gzip is the industry workhorse and should be enabled on every server.
✅ Compression Ratio Analysis
We compare the compressed size of your page to its original uncompressed size, showing you exactly how much bandwidth you're saving.
✅ Header Verification
Audits the Vary: Accept-Encoding header, which is critical for ensuring that proxies and CDNs serve the correct version of your compressed content.
Why Server Compression Matters
| Status | Impact |
|---|---|
| No Compression | High bandwidth costs, slow load times on mobile, lower Google PageSpeed scores. |
| Gzip Only | Good, but missing out on 15-20% additional savings offered by Brotli. |
| Brotli Enabled | Optimal performance. Fast loading and minimum data transfer. |
| Missing Vary Header | Risk of users receiving uncompressed content from intermediate caches. |
Compression Best Practices
Prefer Brotli for HTTPS
Brotli is only supported over HTTPS by most browsers. It provides significantly better compression for static assets like CSS and JavaScript.
Don't Compress Images
Always exclude binary files like JPEG, PNG, or PDF from server compression. These files are already compressed; trying to compress them again wastes CPU cycles and can sometimes increase the file size.
Frequently Asked Questions
Which is better: Gzip or Brotli?
Brotli is generally superior for web content. It results in smaller file sizes than Gzip at the same CPU settings. However, you should enable both to support all browsers.
How do I enable compression?
On Nginx, you use the gzip on; and brotli on; directives. On Apache, you use mod_deflate for Gzip and mod_brotli for Brotli.
Can compression break my site?
No. Browsers that don't support compression simply won't request it, and the server will serve the uncompressed version.
Set Up Continuous Performance Monitoring
The free checker above is great for a manual test, but a server update or CDN change can accidentally disable compression.
With a UpMonitor account, you can:
- ✅ Monitor compression status 24/7
- ✅ Get instant alerts if Brotli or Gzip is disabled
- ✅ Track compression ratios over time
- ✅ Receive warnings for uncompressed large assets
Also useful for this stack
Pair the audit you just ran with these checkers - the failure modes tend to travel together.
Performance
Measures Time to First Byte (TTFB), total response time, and body size. Grades TTFB as success (≤500ms), warning (≤1000ms), or failure (>1000ms).
Page Weight
Measures the size of the initial HTML document and counts declared <script>, <link rel=stylesheet>, <img>, and <iframe> tags. Warns above 500 KB; fails above 2 MB.
Liveness & Routing
Consolidated liveness audit: follows redirect chains, verifies secure HTTPS upgrades, measures response timing, and captures final headers.
Stop running this audit by hand.
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