Privacy: your files never leave your device

Where processing happens

All file processing happens locally, in your browser. When you add a file, the browser reads it with the standard File API, validates its type (extension, MIME type and magic bytes), and hands the bytes to a Web Worker running on your device. The processing engines are JavaScript and WebAssembly, loaded on demand from this site.

The bytes cross from the main browser thread to the worker by transfer, not by network copy. There is no upload API in the processing pipeline — not an unused one, none at all.

What the server sees

CompressKit has a backend, but it exists only for accounts, usage limits and payments: your email address (from Google, when you sign in), payment identifiers and purchase state, and usage counters — which format and operation ran and the declared file size in bytes, used to enforce the free tier. That is the complete list of what it ever receives.

File bytes, file contents, extracted text and filenames are never transmitted to the backend, and they never appear in analytics or logs — the usage counter knows that a PDF was compressed, never what was inside it or what it was called. Any request containing them outside the documented account endpoints would be a defect by our own written standards.

What is stored on your device

Results are held in memory as temporary download links and released when you're done — there is no cloud copy because there is no upload. Your theme preference is stored in your browser's localStorage; that is the only persistent data the site writes. Files are not persisted to IndexedDB by default.

Analytics and tracking

No advertising trackers are embedded. No document contents, filenames or account details appear in any measurement — the entire file workflow (drop zone, file list, job queue, results and downloads) is excluded from capture, and your files are processed in your browser, never transmitted.

If you prefer no measurement at all, any tracker blocker stops it completely, and every tool keeps working — the site does not depend on it.

You can verify this

You don't need to take our word for it. Open your browser's developer tools, watch the Network tab, and compress a file: you will see no request carrying your file's data. The site's automated tests include network-interception checks that assert exactly this behavior.

Questions about this page or your account data: support@compresskit.site.