7-Zip Online Free — Compress and Extract 7z in Your Browser

What Makes 7z the Best Compression Format?

7-Zip uses the LZMA2 algorithm, which builds a large shared dictionary across all files in the archive simultaneously. This "solid archive" approach means closely related files — like source code files in the same project — compress together far more effectively than they would individually in a ZIP.

The result is typically 30–70% better compression than ZIP on text-based content, and up to 10x better on repositories full of similar files. The trade-off is speed: LZMA2 is slower to compress and decompress than DEFLATE, and the format requires 7-Zip to be installed on the recipient's machine.

7z vs ZIP vs TAR.GZ — Format Comparison

How to Use 7-Zip Online — Step by Step

Compressing files into a .7z archive

1. Open the 7-Zip Online tool and select the Compress tab.
2. Drop your files onto the dropzone or click Browse.
3. Click Create 7z Archive. The 7-Zip WASM engine loads on first use (~1.6 MB, cached after that), then compresses your files.
4. Download archive.7z.

Extracting a .7z archive

1. Switch to the Extract tab.
2. Drop your .7z file onto the dropzone.
3. Click Extract Files.
4. Download each extracted file individually from the results list.

How the WebAssembly Engine Works

The tool uses 7z-wasm, which is the official 7-Zip source code compiled to WebAssembly via Emscripten. This means you get the identical compression algorithm as the desktop application — not a reimplementation or approximation.

The WASM binary (~1.6 MB) is served as a static file and loads on first use. Your browser caches it, so subsequent visits start instantly. All computation happens in your browser tab — your files never touch a server.

Advanced Use Cases

Compressing a software release for distribution

7z is common for distributing Windows software because its compression ratio significantly reduces download size. Create the archive here, test it, then distribute the.7z alongside a note that recipients need 7-Zip to extract it.

Maximum compression for source code archives

A repository full of .js, .ts, or .py files is ideal for LZMA2. The solid archive approach means similar code patterns across files compress together. A typical 50 MB Node.js project (with node_modules excluded) often compresses to under 5 MB.

Opening 7z archives on Windows without installing software

On a locked-down work machine where you cannot install 7-Zip, this tool extracts .7z files directly in the browser. Switch to the Extract tab, drop the archive, and download the files you need.

When to use ZIP instead

If the recipient may not have 7-Zip installed, use the ZIP Compressor instead. ZIP is natively supported on every operating system with no extra software. Both tools are free and run in the same browser.

Common Questions

Is this the real 7-Zip engine?

Yes. It uses the official 7-Zip source compiled to WebAssembly. The compression algorithm and output format are identical to the desktop application.

Why does it take a moment to start on first use?

The WebAssembly binary (~1.6 MB) loads once per browser session. After the first use, your browser caches it and subsequent operations start instantly.

Are my files uploaded to a server?

No. The WASM binary is a static file served from this site's CDN. Your actual data files are never sent anywhere — all processing happens inside your browser tab.

What 7z features are not supported?

Password-protected archives and multi-volume archives are not currently supported in the browser version. For those features, the desktop 7-Zip application is recommended.