Paste code or drop files to see how big they really are over the wire with gzip and Brotli, how much compression saves, and how long each takes to download.
1 Text or a file 2 processed on your device 3 gzip + Brotli sizes
Gzip & Brotli Size Checker
Text or files
Up to 50 files. They stay on your device.
Compressed sizes
Item
Raw
gzip
Brotli
Download time (all items)
Network
Uncompressed
Compressed
01
What it does
Compresses text or files with the browser's gzip, deflate and, where supported, Brotli to show real transfer sizes and times.
Real compression with the browser's CompressionStream
gzip, deflate and Brotli where available
Several files at once
Download times on common networks
02
Private by design
Everything happens in your browser. Nothing you type, paste or upload is sent anywhere, and it keeps working offline once the page has loaded.
03
What you get
Compressed sizes and timings, with a Copy and a Download button on every result.
Gzip
Brotli
Performance
Why it matters
File sizes on disk aren't what users download: servers compress text with gzip or Brotli, often by 70 to 80 percent. To know whether a library or stylesheet is really heavy, you need the compressed size.
This checker compresses your text or files on your device with the browser's own compression engine, so the numbers are real, not estimated, and shows the download time on typical networks. It also tells you when a file won't compress because it's already compressed.
How it works
InputHTML, CSS, JS, JSON or SVG
In your browserCompressed by the browser's own codecs
OutputSizes, savings and download times
Where it fits in a designer's workflow
Plan
Design
Build
Test
Launch
Checking what a file really costs.
By the numbers
Measured at build time with Python's gzip and Brotli at their highest levels. Text shrinks to about a fifth; the JPEG barely changes because it's already compressed, so there's no point compressing images on the server. Source: RFC 7932: Brotli.Show the numbers as a table
File
Raw
gzip -9
Brotli 11
Home page (index.html)
53,692
10,784
8,742
Main stylesheet (styles.css)
37,352
9,383
8,246
Tool kit script (kit.js)
9,941
3,726
3,234
Tool icon (SVG)
401
266
241
Sample photo (JPEG)
38,778
38,663
38,586
How to use it
Paste text, or drop one or more files.
Read the raw and compressed sizes.
Choose a network to see download times.
Compare minified and unminified versions.
FAQ
Is Brotli supported?
Where the browser's CompressionStream offers it. Otherwise gzip and deflate are shown, and Brotli is typically 15 to 20 percent smaller than gzip for text.
Why don't images shrink?
JPEG, PNG, WebP and AVIF are already compressed. Servers usually skip gzip for them.
Is this the same level as my server?
Browsers use a standard level. Servers can use higher levels for static files, so your server might do slightly better.
I build fast, accessible websites and web apps that pass these checks from day one. Tell me about your project and I'll reply personally with honest next steps.
