Shrink PDFs without uploading them
Compress PDF files to a much smaller size with three quality levels, processed entirely on your device.
For the best results: Balanced mode suits email attachments; Maximum is for strict upload limits. Compression rasterizes each page, so text stops being selectable, keep the original for editing and archiving.
Advanced settingsoptional, defaults work well
Processed entirely in your browser, your files are never uploaded to any server, and nothing is stored.
What is Compress PDF?
Compress PDF is a free PDF tool that re-renders each page of a PDF as an efficiently compressed image and rebuilds the document, cutting file size dramatically on your own device. The document is rendered page by page inside your browser, so its contents never leave your device. There is no upload queue, no watermark on the result, and nothing to install or sign up for.
- ✦Runs entirely in your browser. Nothing you enter is ever uploaded
- ✦No account, no sign-up, and no data leaves your device
- ✦Works offline once the page has loaded
See it in action
A 12-page property report full of photos weighs 8.2 MB, and the portal it has to go to caps uploads at 2 MB.
What you drop in
report.pdf (8.2 MB, 12 pages), advanced setting "Compress to target size" set to 2 MB
What you get
compressed PDF, 1.86 MB, all 12 pages intact, pages re-rendered as efficiently packed images. Done in about a minute and a half on a laptop, entirely offline.
Tip: The target-size mode searches for the best quality that fits under your number, so give it the real limit rather than guessing a level. And if your PDF is mostly crisp text, the tool checks a sample first and tells you within seconds that the original is already smaller, instead of wasting minutes to find that out.
Use cases
What people use it for
Shrink a scanned rental application below an email attachment limit before sending it to the agent.
Reduce a photo-heavy school newsletter so parents on mobile data can download it quickly.
Slim an exported presentation PDF before uploading it to a portal with a strict size cap.
Who uses Compress PDF?
Renters and buyers
compress scanned applications and signed contracts under the size limits that agent portals and inboxes impose
Office administrators
shrink scan-heavy paperwork so it moves through document systems and email without bouncing back
Community volunteers
make photo-filled newsletters and minutes small enough for members on slow connections to open
How it works
- 1Choose your PDF or images. They load into your browser only.
- 2Your device does the edit: merge, split, rotate, or convert, with no upload.
- 3The result downloads straight back to you; nothing is kept.
Tips for the best results
- Keep the original file, since the compressed copy loses its selectable text permanently.
- Try the strongest level first on scans, and step back only if artefacts appear.
- If the file barely shrinks, it was already efficient, so send the original instead.
- Compress big documents on a computer, because every page renders in browser memory.
- Check any fine print at your chosen level before the file goes anywhere official.
FAQ
Frequently asked questions
How does the compression actually make my PDF smaller?
Behind the button, pdf.js, the engine Firefox uses to display PDFs, draws each page onto a canvas exactly as it would appear on screen. That drawing is saved as a JPEG at your chosen level, and pdf-lib assembles the images into a fresh document. Scans and photo-heavy pages shrink dramatically, because JPEG discards visual detail human eyes rarely miss.
Why is the text no longer selectable after compressing?
Because every page has been rebuilt as a single picture. An ordinary PDF stores its words as vector instructions, tiny commands that say draw this letter at this position, which is why you can highlight and copy them. After re-rendering, those letters are just pixels inside a JPEG. Keep the original for editing and searching, and treat the compressed copy as the version you send.
What do the three compression levels change?
They trade size against fidelity by setting how hard each page's JPEG is squeezed. The gentlest level preserves fine detail for documents people will study closely, the middle suits everyday sharing, and the strongest produces the smallest files while letting subtle textures soften. Whichever you pick, glance over any small print in the result before it goes anywhere important.
Why did my PDF barely shrink at all?
Some PDFs are already about as small as they can honestly be. A document that is mostly crisp vector text costs almost nothing to store, because describing letters as drawing commands is far cheaper than photographing them. Re-rendering such pages as images can match or even exceed the original size. Compression earns its keep on scans, photos and heavy graphics.
Is my PDF uploaded anywhere while it compresses?
It never leaves your machine at any point. Every page is rendered and reassembled inside the browser tab itself, working purely in local memory, and the finished file arrives as a download from that same memory. Bank statements, contracts and medical letters gain no second copy anywhere, because no server is involved in the work at all.
Does this PDF compressor use artificial intelligence?
No, and the job would gain nothing from it. The pipeline is fixed: render each page, encode it as a JPEG at your chosen level, rebuild the document. Identical input and setting give an identical result every run, which keeps the process predictable, quick and entirely private to your device.
How do I compress a PDF that is too big to email?
Open the compressor, drop the file in, choose the strongest of the three levels, and download the smaller copy. There is no account, watermark or upload step, and the work happens on your own device. If the result still will not fit, set an exact target size in megabytes under advanced settings and let the tool work out the quality that gets you under it.
Why is my compressed PDF blurry when I zoom in?
Each page is now a picture at a fixed resolution, so zooming enlarges pixels instead of redrawing perfect letters the way vector text allows. At normal reading size the difference is minor, but deep zoom exposes it. Choose a gentler level for documents people will magnify, and keep the sharp original regardless.
Are there any usage limits?
None. Everything is generated locally in your browser, so there is no server cost, no metering, and no daily cap, use it as many times as you like, completely free.
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