How to compress a PDF
- Drop your PDF into the box above (or click to browse).
- Pick a compression level — Light, Balanced, or Maximum.
- Click Compress PDF and download the smaller file.
How it works
localdobe’s compression is powered by pdfcpu, compiled to WebAssembly and run inside a Web Worker in your browser. Instead of uploading your document to a server for processing, the same battle-tested Go PDF engine that powers pdfcpu’s command-line tool runs directly on your device — no upload, no queue, no server round-trip. The first run downloads the engine once (a one-time download, cached after that); every run after that starts instantly, even offline.
Compression itself works by removing redundancy rather than recompressing images: duplicate fonts, unused objects, and repeated content streams are deduplicated and stripped out. Want the full technical breakdown? Read how PDF compression actually works.
Frequently asked questions
How much smaller will my PDF get?
It depends on the file. PDFs with duplicated fonts, images, or content streams shrink the most — often 20–70%. Already-optimized PDFs may not shrink at all, and we’ll tell you honestly when that happens.
Is quality reduced?
No. localdobe removes redundancy (duplicate fonts, unused objects, repeated streams) rather than recompressing your images, so pages look identical.
Why is the first compression slow?
Your browser downloads the compression engine once (a few MB compressed), then caches it. After that it starts instantly — even offline.
Is my PDF uploaded?
No. The engine runs inside a Web Worker in your browser. Your file never touches a server.