Compress PDF — Free, No Upload
Shrink PDF file size — free, private, and entirely in your browser.
How to compress a PDF in your browser
Need to compress PDF files so they’re small enough to email or upload? You can shrink a PDF here in a few clicks, without uploading it anywhere. Choose a file, pick how hard to compress, and download a smaller version — all processed locally so your document never leaves your device. That privacy matters when the file is a contract, a scanned ID, or a financial statement.
Here’s how:
- Open your PDF. Drag it onto the upload area or click to choose it.
- Pick a compression level. Low keeps the best quality, Recommended is a balanced default, and High makes the smallest file.
- Click “Compress PDF.” The first run loads the compression engine (about 15 MB, one time per visit); after that it’s quick.
- Check the result. You’ll see the exact before and after sizes and the percentage saved.
- Download. Save the smaller
compressed.pdfto your device.
If a PDF is already well-optimized, compression may not make it much smaller — the tool tells you honestly rather than handing back a bigger file and calling it a win.
Why use a browser-based PDF tool?
Most popular online PDF compressors — SmallPDF, iLovePDF, Adobe’s web tools — upload your file to their servers to compress it, then send it back. For a document that may hold sensitive information, that means trusting a third party with a copy of it.
This tool is different. Compression is done by Ghostscript, the same engine many desktop tools use, compiled to WebAssembly and run in your browser. Your file is processed in memory on your own machine and never transmitted. The only thing downloaded is the compression engine itself — you can watch the Network tab and confirm your PDF is never uploaded.
The trade-offs are all in your favor: real privacy, no upload or download waiting once the engine is cached, and a tool that keeps working offline.
What compression actually does
PDF size is usually dominated by images. Compressing a PDF mainly downsamples and re-encodes those images to a lower resolution, which is why:
- Scanned documents and photo-heavy PDFs shrink the most. A 40 MB scan can often drop to a few megabytes.
- Text-only PDFs barely change. There’s little to compress when the file is already just text and vectors.
- Higher compression means lower image quality. The High setting reduces resolution the most; Low preserves near-print quality.
Choosing a level
| Level | Best for | Quality | Size |
|---|---|---|---|
| Low | Printing, archiving | Highest | Largest of the three |
| Recommended | Everyday documents, sharing | Balanced | Medium |
| High | Email, web upload, screen viewing | Lower | Smallest |
When in doubt, start with Recommended, check the before/after numbers, and step up to High if you need it smaller and the quality still looks fine.
Tips and things to know
- The first run is the slow one. Loading the ~15 MB engine happens once per visit, then compression is fast.
- Already small? It may not shrink. Optimized or text-only PDFs have little to give up — that’s normal.
- Encrypted PDFs need unlocking first. If your file is password-protected, remove the password with the Unlock PDF tool, then come back and compress.
- Combine first if needed. Merging several files? Use Merge PDF first, then compress the combined document.
Compress PDF vs. upload-based tools
| This tool | Typical upload tools | |
|---|---|---|
| Where files are processed | Your browser | Their servers |
| Files uploaded | Never | Yes |
| Signup required | No | Often |
| Works offline | Yes (after first visit) | No |
| Engine | Ghostscript (WASM) | Varies |
After compressing, you might want to split out just the pages you need or merge it with other files. For more on the format, see the PDF specification.
FAQs
- Is compressing PDFs here really private?
- Yes. Your PDF is never uploaded. Compression runs entirely in your browser using Ghostscript compiled to WebAssembly, so the file stays on your device. You can confirm it — open your browser's developer tools, switch to the Network tab, and compress a file. The only download you'll see is the one-time compression engine, never your document.
- How much smaller will my PDF get?
- It depends heavily on what's inside. PDFs full of high-resolution scans or photos can shrink dramatically, while files that are mostly text — or already optimized — may shrink little or not at all. After compressing, the tool shows you the exact before and after sizes so you can decide whether to keep the result.
- What do the three levels mean?
- They trade size against quality by changing how images are downsampled. Low compression keeps the best quality (around print resolution), Recommended is a balanced middle ground for everyday documents, and High compression makes the smallest file by reducing image resolution the most.
- Why is the first compression slower?
- The first time you compress, your browser downloads the compression engine — about 15 MB of WebAssembly — and prepares it. That's a one-time cost per visit; it's cached afterward, and your file itself is never uploaded.
- Is there a file-size limit?
- There's no hard limit, but files over 100 MB show a warning because compression runs on your own device and very large files can be slow or memory-heavy. Smaller files compress in seconds.
- Will compressing reduce quality?
- Compression mainly works by lowering the resolution of embedded images, so some quality loss is possible — more at higher compression levels. Text generally stays crisp. If a result looks too soft, try a lower compression level.
- What if my PDF is password-protected?
- An encrypted PDF must be unlocked before it can be compressed. The tool will detect this and link you to the Unlock PDF tool, which removes a password you already know.
- Does this work offline?
- Yes. After your first visit — once the engine is cached — the tool works with no internet connection.