File Compressor

How it works

This file compressor uses the CompressionStream API built into modern browsers to compress files with gzip. It also supports decompressing gzip files using DecompressionStream. All processing happens locally in your browser. No files are uploaded. Works in Chrome, Edge, Firefox, and Safari.

Select a file and click Compress to create a gzip-compressed version. Switch to Decompress mode to extract the contents of a .gz file. The tool shows file sizes before and after so you can see the compression ratio.

Want proof? Open your browser's developer tools and watch the network tab while you work: your files never upload.

Frequently asked questions

What format does it produce, and what can it decompress?

Compress mode wraps your file in a single gzip stream and adds a .gz extension. Decompress mode only reads valid gzip data; it is not a general archive extractor, so ZIP, 7z, tar, and other formats will fail with an error.

Why did my file barely shrink, or come out larger?

Formats like JPEG, PNG, MP3, MP4, and ZIP are already compressed, so gzip finds little redundancy to remove and may even add a few bytes of overhead. Gzip is most effective on text-based data such as JSON, CSV, HTML, logs, and source code.

Is there a maximum file size?

There is no fixed cap, but the entire file is loaded into memory and processed in one pass. Very large files can exhaust your device's available RAM, especially on mobile, so multi-gigabyte inputs may fail.

Can it compress several files or a whole folder at once?

No. Each run handles one file and outputs one .gz, because gzip is a single-stream format with no folder structure. To bundle multiple files, archive them into a tar or ZIP with another tool first, then gzip that single archive here.

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