Compress PDF
Shrink PDF file size locally in your browser sandbox. Private, offline PDF compression with no server uploads.
PDF Vault compresses a PDF by re-encoding and downsampling its images in your browser, typically cutting scan-heavy files by 40-70% without uploading them.
Almost every PDF that is too big to email is too big for the same reason: it contains images captured at far higher resolution than anyone will ever look at. A phone-scanned contract can easily be 20 MB of pixels representing a page of black text.
Compression here re-encodes those images, downsamples them to a DPI you pick, and rewrites the document's object streams. You choose the balance between size and fidelity, and you see the result before deciding to keep it.
Nothing you do here is uploaded. The file is read into your browser's memory, processed by WebAssembly on your own machine, and written straight back to your downloads folder. You can confirm it yourself: open DevTools, switch to the Network tab, and run the tool — there is no request carrying your document, because there is no server endpoint to receive it.
How to compress a PDF to reduce file size
- Load the PDF you need to shrink.
- Pick a compression level — higher compression means more aggressive image downsampling.
- Run it, then compare the before and after size the tool reports.
- If the quality still looks right, download. If not, try a gentler level and run it again.
What you get
- Choose your tradeoff. Several levels, from light cleanup to aggressive size reduction for email limits.
- Best on scans. Image-heavy and scanned documents see the largest savings, often well over half.
- See the result first. Before and after sizes are shown so you are not guessing.
- Runs on your machine. No upload, which matters because the documents people compress are usually the ones they are about to send somewhere.
Frequently asked questions
How do I get a PDF under a specific size, like 1 MB?
Start with a medium level, check the reported output size, and step up the compression until you clear the limit. Scanned documents usually reach 1 MB comfortably; a PDF that is mostly vector text is already small and will compress less.
Will compression make my text blurry?
Text that is real text stays sharp, because it is not an image. Blurriness only affects embedded pictures and scans, and only at the more aggressive levels.
Why did my file barely shrink?
It was probably already efficient — a text-only PDF exported from Word has little to remove. The big wins come from photos and scans.
Can I compress several PDFs at once?
Compress them one at a time on the Free plan. Pro removes the daily operation limit, so batches are practical.