How much can compress-pdf reduce a PDF?

Typical reductions are 30-70% for image-heavy PDFs in Medium or Low mode and 5-20% for text-heavy PDFs in Lossless mode. The tool tries lossless object-stream optimisation first, then re-renders embedded images if you choose Medium or Low. All processing runs in your browser using pdf-lib.

What does Lossless mode do?

Lossless mode removes structural overhead and optimises the PDF's internal object streams, it never degrades image quality or removes content.

Why is the compressed file sometimes the same size?

If the PDF is already well-optimised, lossless compression may produce little or no reduction. Try a lower quality mode for scanned-image PDFs.

Will compression make text unselectable?

Only image re-rendering modes (Medium and Low) affect text, as pages are converted to JPEG images. Lossless mode preserves all text as fully selectable.

Compress PDF

PDF compressor is a browser-based tool that reduces PDF file size. It offers a lossless mode that strips structural overhead, a re-render mode that rasterises pages at controllable quality, and a side-by-side size comparison before download. The tool runs in your browser.

Drop a PDF here or click to browse

Dedicated pages

Direct links for specific compression tasks.

Compress PDF Online

Compress a PDF file directly in your browser. Choose lossless optimisation or image re-rendering for maximum size reduction. No account required.

Reduce PDF File Size

Make a PDF smaller without uploading it. Lossless or image-based compression modes. Free tool that runs entirely in your browser.

Shrink PDF

Shrink a PDF file in your browser. Choose lossless optimisation or aggressive image-based compression. Free and private.

Compress PDF to 1 MB

Reduce a PDF file to under 1 MB directly in your browser. Try the Medium or Low quality setting for the smallest output. No account required.

Compress PDF for Email

Make a PDF small enough to send as an email attachment. Most email providers cap attachments at 10–25 MB. Free, private, runs entirely in your browser. No account required.

Compress PDF Without Uploading

Compress a PDF file without uploading anywhere. All processing runs locally in your browser using pdf-lib. No account required.

Compress PDF: No Account Required

Compress a PDF file for free with no account, no sign-up, and no watermark. All processing runs in your browser. No registration required.

How to compress a PDF

Drop your PDF onto the upload area or click to browse.
Choose a compression level. Lossless for maximum quality, or Medium or Low for smaller files.
Click "Compress PDF" and wait while your browser processes the file.
Download the compressed PDF and check the before and after size comparison.

Common uses

Reducing PDF size before emailing it as an attachment to avoid size limits, use merge PDF to combine files first, then compress the result
Compressing scanned PDFs to save storage space
Shrinking large PDF reports before uploading them to a web portal. Split out the relevant pages first for even smaller file sizes

Technical specification

Algorithm or formula: Lossless mode uses object-stream rewriting (no quality loss). Medium and Low modes render each page with pdfjs-dist, then re-embed the rasterised JPEG at scale 1.5x or 1.2x or 0.9x with JPEG quality 0.85, 0.7, or 0.55.
Browser API or library: pdf-lib 1.17 for object writing, pdfjs-dist 5.7 for rendering. Both lazy-loaded from npm.
Input limits: PDFs capped at 100 MB to keep parsing inside browser memory budgets.
Output: PDF blob with a download link, accompanied by a before-and-after size badge.
Known limitations: Re-render modes flatten text to images, so the result is no longer text-selectable. Encrypted PDFs cannot be re-saved without the password.

Frequently asked questions

Is my PDF uploaded to a server?: No. Compression happens entirely in your browser using pdf-lib.
What does Lossless mode do?: Lossless mode removes structural overhead and optimises the PDF's internal object streams, it never degrades image quality or removes content.
Why is the compressed file sometimes the same size?: If the PDF is already well-optimised, lossless compression may produce little or no reduction. Try a lower quality mode for scanned-image PDFs.
Will compression make text unselectable?: Only image re-rendering modes (Medium and Low) affect text, as pages are converted to JPEG images. Lossless mode preserves all text as fully selectable.

Reviewed and tested May 26, 2026.