Compress PDF
This tool reduces PDF file size by re-rendering every page as a compressed JPEG image and assembling a new PDF from the results. You pick one of three levels that trade resolution and image quality against size. Everything happens in the browser: the file is opened, processed and rebuilt on your own device and never leaves it.
100% in your browser. Your file never leaves your device.
Features
- Three levels trade image resolution and JPEG quality against the resulting file size.
- Processing runs entirely in your browser; the PDF is never uploaded to a server.
- Shows the achieved size reduction as a percentage once compression has finished.
- Most effective on scans, photo pages and other image-heavy documents such as brochures.
- The result is a standard PDF that opens in any common viewer.
- Works in current desktop and mobile browsers without any installation or account.
About this tool
Under the hood, two open-source libraries share the work. pdf.js — the same renderer Firefox uses — opens your document and draws each page onto an invisible canvas at the resolution of your chosen level. The canvas content is then encoded as a JPEG image. Finally, pdf-lib creates a brand-new PDF and embeds exactly one of these images per page.
The three levels control two parameters: render resolution and JPEG quality. Low keeps the highest resolution and applies the mildest compression, Medium is the balanced default, and High renders at reduced resolution with strong compression for the smallest files. Because pages are turned into pictures, text and vector graphics get rasterised — a deliberate trade-off that makes the big savings possible.
Your file is read into memory inside the browser tab and processed there; no part of it is transmitted anywhere. That also means speed depends on your own device rather than on a server. The finished PDF is offered for download with a "-compressed" suffix, and your original stays unchanged. If you need to keep searchable text, the Optimize tool is the better fit.
How to compress a PDF
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Select your PDF
Drag your PDF onto the drop zone or click the button below it to open the file picker. The tool handles one file per run; once the file is loaded, its name and size are displayed above the options.
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Choose a compression level
Pick Low, Medium or High in the segmented control. Low favours quality, High favours the smallest file, and Medium — preselected by default — is a sensible compromise for most documents.
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Start the compression
Click the Compress button to begin. If you picked the wrong file, Cancel takes you back to the drop zone at any time so you can choose another document.
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Wait for local processing
A loading spinner is shown while each page is rendered and re-encoded as a JPEG on your device. How long this takes depends on the page count and your hardware — large scans need a bit longer.
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Save the compressed file
When processing finishes, a notice reports how many percent smaller the result is. Depending on your browser, the new PDF — with "-compressed" added to its filename — is saved via a dialog or direct download; your original stays untouched.
Typical use cases
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Getting attachments under email limits
A scanned contract or a slide deck full of photos quickly exceeds the 20–25 MB cap most mail providers enforce. After a run at Medium or High, the attachment usually fits with room to spare — and the recipient still gets a perfectly normal PDF they can open and print without extra software.
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Uploading to portals with size caps
Application portals, university platforms and government forms often reject files above a few megabytes. Because the compression runs locally, sensitive paperwork such as payslips, certificates or ID scans never touches a third-party server along the way — you shrink the document on your own machine and upload only the finished file to the portal itself.
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Archiving scanned paperwork compactly
Scanners at high DPI settings produce huge PDFs — a ten-page scan can easily reach 50 MB. If the copies are only for your own records, the Medium level cuts their size drastically while keeping them perfectly readable, so far more documents fit into the same cloud storage or onto the same backup drive.
Tips & limitations
- Text and vector graphics are rasterised: the compressed PDF is no longer searchable, and its text cannot be selected or copied. If you still need that, use the Optimize tool instead.
- Everything runs in a single browser tab, so very large documents — hundreds of pages or high-resolution scans — take time and plenty of memory. Splitting the file first with the Split tool helps.
- Start with Medium and check the result. If the file is still too big or the quality disappoints, go back to your original and try a different level.
- Compression is lossy and cannot be undone, so keep the original file. The tool never modifies it — the output is always a separate, newly created PDF.
Frequently asked questions
How much smaller will my PDF get?
That depends on the content. Image-heavy documents such as scans often shrink by 50–80 %, while text-only PDFs may barely change or even grow, because their pages are converted into images. The tool shows you the exact saving after each run.
Will the text stay selectable and searchable?
No. Every page is converted into a JPEG image, so the text becomes part of the picture: it stays readable, but you can no longer select, copy or search it. If you need that again later, only a subsequent text recognition (OCR) pass can bring it back.
Is my file uploaded to a server?
No. pdf.js and pdf-lib run as JavaScript directly in your browser; the document is opened, rendered and rebuilt entirely on your device. No file content is transmitted — you can verify this yourself in your browser's network tools.
Which level should I choose?
Medium is a good default for email and everyday sharing. Choose Low when appearance matters — for instance with fine print or detailed images — and High when the file simply has to be as small as possible, such as for strict upload limits.
Can I compress password-protected PDFs?
No. The browser version cannot open encrypted files; the process stops with an error message. Remove the password protection first with a tool that can decrypt the file, then compress the unprotected copy.
Why did my PDF barely shrink?
PDFs that already contain strongly compressed images, or that consist purely of text, leave little room for savings. The rebuilt file can even come out larger than the original; in that case the tool reports a saving of 0 % and you are better off keeping the original.
Are bookmarks, links and form fields preserved?
No. Because the output is a freshly built PDF containing one image per page, all interactive elements — bookmarks, hyperlinks, form fields, annotations — as well as the document metadata are lost. If you need to keep the document structure, use the Optimize tool instead of compressing.
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