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Security and networkingChecked through WebDiag API

HTTP Compression Checker

Enter a URL to check gzip/Brotli/deflate compression and cache-safe Vary behavior.

  • gzip / br
  • Vary
  • text assets
Online tool

Try the tool

Enter a URL: WebDiag will run a safe network check and show the result.

URL

Network check through backend

For HTTP/SEO tools, the URL is sent to the WebDiag API, where SSRF protection, DNS/IP policy, and redirect limits are applied.

Reviewed: 2026-07-17
01

How to use it

  1. 1

    Enter a public http/https URL.

  2. 2

    Run the compression policy check.

  3. 3

    Review Content-Encoding, content type, and Vary header.

02

What the tool can do

  • Checks Content-Encoding and compressible candidate response.
  • Checks Vary: Accept-Encoding for shared-cache correctness.
  • Runs through SafeHttpFetcher with SSRF protection.
03

Common use cases

  • Find an uncompressed HTML/CSS/JS response.
  • Check Vary before CDN/cache configuration.
  • Prepare a site for speed/Core Web Vitals optimization.
04

How it works inside

The tool does not download a large body and does not build a network waterfall.

Use Page Weight Analyzer and PageSpeed Checker for full page-weight evaluation.

05

Questions and answers

Do I always need Brotli?

Brotli is usually preferable for HTTPS text assets, but gzip fallback remains normal practice.

Why are images not compressible?

JPEG/WebP/AVIF/PNG are already format-compressed; optimize them through image tools, not HTTP gzip.