HTTP Response Size Analyzer
Paste HTTP response headers and body to see uncompressed, GZIP, DEFLATE, and Brotli sizes side by side. Validates Content-Encoding, checks for missing Vary headers, and gives actionable compression recommendations. Runs entirely in your browser with no signup required.
Paste HTTP response headers and body to see uncompressed, GZIP, DEFLATE, and Brotli sizes side by side. Checks Content-Encoding, validates Content-Length, and gives actionable compression recommendations. Runs entirely in your browser.
Load an example:
Paste the raw HTTP response headers (including status line)
Paste the raw response body (JSON, HTML, CSS, etc.)
Why Use Our HTTP Response Size Analyzer?
Instant HTTP Response Analysis
Paste any HTTP response and instantly see uncompressed, GZIP, DEFLATE, and Brotli sizes side by side — with exact byte counts and reduction percentages.
Secure HTTP Response Analyzer Online
All compression and analysis run entirely in your browser. Your response data never leaves your device — safe for analyzing responses containing sensitive API data.
Header Validation & Recommendations
Checks Content-Encoding, validates Content-Length, detects missing Vary headers, and gives actionable recommendations for each response.
100% Free Forever
Analyze as many HTTP responses as you need, completely free. No account, no subscription, no file size limits, and no ads.
Common Use Cases for HTTP Response Size Analyzer
API Response Optimization
Paste a JSON API response to see exactly how much bandwidth GZIP and Brotli compression would save — quantify the impact before enabling compression on your server.
Core Web Vitals & PageSpeed
Analyze HTML, CSS, and JS responses to identify uncompressed assets that are hurting your PageSpeed score — get specific byte savings for each resource.
Debugging Compression Issues
Verify that Content-Encoding headers are correct, check that Content-Length matches actual body size, and confirm Vary: Accept-Encoding is present.
Server Configuration Validation
After enabling GZIP or Brotli on nginx or Apache, paste the response to confirm compression is working and measure the actual savings achieved.
Bandwidth Cost Planning
Calculate the bandwidth savings from enabling compression across your API — multiply the per-response savings by your request volume to estimate monthly cost reduction.
Security & Privacy Auditing
Analyze response headers for missing Cache-Control directives, incorrect Content-Length values, and other header issues that could affect security or caching behavior.
Understanding HTTP Response Compression
What is HTTP Response Size Analysis?
HTTP response size analysis is the process of measuring how large an HTTP response is in its raw form and how much smaller it would be with GZIP, DEFLATE, or Brotli compression applied. Web servers can compress text-based responses (HTML, JSON, CSS, JavaScript) before sending them to the browser, reducing transfer size by 60–90%. Our free HTTP response size analyzer performs this analysis entirely in your browser using the native CompressionStream API — no server upload required.
How Our HTTP Response Size Analyzer Works
- Paste Headers and Body: Copy the raw HTTP response headers and body from your browser DevTools, curl output, or API client and paste them into the two panels.
- Instant Browser-Based Analysis:Click "Analyze Response" — the tool compresses the body with GZIP, DEFLATE, and Brotli in parallel using the browser's native CompressionStream API. Your data never leaves your device.
- Review Results and Recommendations: See the size comparison chart, parsed headers table, and actionable recommendations for improving compression.
What Gets Analyzed
- Body Compression: The response body is compressed with GZIP, DEFLATE, and Brotli — showing exact sizes and reduction percentages for each.
- Content-Encoding: Checks whether the response is already compressed and validates the encoding value against known compression formats.
- Content-Length: Validates that the declared Content-Length matches the actual body size — mismatches can cause connection issues.
- Vary Header: Checks for the required
Vary: Accept-Encodingheader that ensures CDNs and proxies cache compressed and uncompressed versions separately.
GZIP vs Brotli for HTTP Responses
GZIP is the most widely supported HTTP compression format — all browsers and servers support it. It typically achieves 60–80% size reduction for JSON and HTML. Brotli achieves 15–25% better compression than GZIP at the same quality level and is supported by all modern browsers (Chrome, Firefox, Safari, Edge). For maximum bandwidth savings, enable Brotli as the primary compression with GZIP as a fallback for older clients.
Related Tools
JSON Key Shortener
Shorten verbose JSON keys to single letters or abbreviated forms — shows size reduction and provides a downloadable key mapping file for restoration. Free online JSON key shortener.
JSON vs MessagePack Size Comparison
Compare JSON byte size vs MessagePack encoding for any payload — shows exact savings, type-by-type breakdown, and MessagePack hex preview. Free online JSON vs MessagePack comparison.
String Decompressor (GZIP/LZ)
Decompress GZIP+Base64, DEFLATE+Base64, and LZ-String compressed payloads back to readable text — supports all three LZ-String variants. Free online string decompressor.
ZIP File Extractor
Extract files from any ZIP archive client-side — browse contents, preview text files, download individual files or all at once. Free online ZIP extractor, no signup required.
Frequently Asked Questions About HTTP Response Size Analyzer
An HTTP response size analyzer measures how large an HTTP response is uncompressed and how much smaller it would be with GZIP, DEFLATE, or Brotli compression. Our free online HTTP response size analyzer runs entirely in your browser — no signup or server upload required.
Open your browser DevTools (F12), go to the Network tab, click on any request, and copy the Response Headers and Response body. Alternatively, use curl with the -i flag to include headers in the output, or copy from your API client (Postman, Insomnia, etc.).
Yes, complete privacy is guaranteed. All compression and analysis run entirely client-side in your browser using the native CompressionStream API. Your response data — including any sensitive API payloads — never leaves your device and is never uploaded to any server.
Yes. The HTTP response size analyzer is 100% free with no signup, no subscription, no data size limits, and no ads. You can analyze as many responses as you need.
Content-Encoding: gzip means the server has already compressed the response body with GZIP before sending it. The body you paste should be the decompressed version for accurate analysis. If you paste the compressed body, the tool will show it as already small and compression savings will appear minimal.
Brotli compression via the CompressionStream API requires Chrome 80+, Edge 80+, or Safari 17.4+. If your browser does not support it, the tool estimates Brotli size as approximately 85% of the GZIP size, which is a reasonable approximation. For exact Brotli measurements, use Chrome or Edge.
The Vary: Accept-Encoding header tells CDNs and caching proxies to store separate cached versions for compressed and uncompressed responses. Without it, a CDN might serve a GZIP-compressed response to a client that does not support GZIP, causing garbled output. Always include this header when serving compressed responses.
Text-based formats compress extremely well: JSON (60–80% reduction), HTML (65–85%), CSS (70–85%), JavaScript (60–80%), XML (70–85%), and plain text (50–75%). Binary formats like images (JPEG, PNG, WebP), videos, and already-compressed archives gain little or nothing from HTTP compression and should not have it enabled.