Compress PDF online for free. Shrink your pdf's file size in seconds — fast, secure, and with no software to install.
This free tool will compress PDF files in the browser — upload a PDF and PDF4 rewrites it with smaller images and tighter internal structure, so the result is easier to email, attach, or upload to a portal with a hard size cap. No signup, no watermark, no installer.
The biggest savings almost always come from images. A typical PDF that looks bloated is one where photos or scans were embedded at print resolution (300+ DPI) but only ever viewed on a screen. PDF4 downsamples those images to a sensible web/email DPI and re-encodes them, which is where most of the size reduction comes from. It also strips redundant metadata and unused objects. Text-only PDFs and files that are already small won't shrink much — they're not the bottleneck.
If compression alone isn't enough, combine it with a few structural tricks. Flatten PDF removes interactive form fields and annotations that bloat the file. Extract PDF Pages lets you keep only the pages you actually need to send. And if you're stitching several files together first, Merge PDF followed by a single compress pass usually beats compressing each part separately.
For batch optimization — think a folder of invoices or a queue of uploaded documents — the same compression is exposed in the PDF4 API and available to AI agents over MCP, so a script or an agent can shrink files on your behalf.
Yes. You can shrink your PDF's file size right here online for free — no account, email, or credit card required. Sign up only if you want higher limits, larger files, or API access.
Yes. Uploads travel over an encrypted HTTPS connection, are processed on our servers, and are automatically deleted within a few hours. We never share or sell your documents.
No. PDF4 works entirely in your web browser, so there is nothing to download or install. It runs on Windows, macOS, Linux, Android, and iOS.
It depends almost entirely on what's inside. Image-heavy PDFs — scans, photo-rich reports, decks — typically shrink dramatically because images are downsampled to a screen-friendly DPI. Text-only PDFs are already lean and won't change much. There's no fixed percentage to promise honestly.
PDF4 aims for visibly clean results at screen sizes by re-encoding images at a sensible DPI. For email, web, and most everyday sharing the difference is hard to notice. For print masters or archival copies, keep the original uncompressed file.