Compress PDF
Compress your PDF files to reduce file size while maintaining quality. Perfect for email attachments, web uploads, and saving storage space.
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Why PDFs get large, and what compression removes
Most oversized PDFs are oversized for one reason: images. A page scanned at 600 DPI in full colour can be several megabytes on its own, and a phone-photographed document often embeds the original camera JPEG at full resolution even though it is displayed at a fraction of that size. Embedded font subsets, duplicated logos on every page, and leftover revision data add the rest.
Compressing a PDF means re-encoding those images at a sensible resolution and quality, dropping data the viewer never displays, and rewriting the file's object streams more efficiently. Text and vector graphics are unaffected — they are mathematical descriptions and already tiny. This is why a text-heavy report barely shrinks while a scanned contract can drop by 80 to 90 per cent, and why every compressor involves a trade-off you control: smaller file versus visibly softer images.
Why we built this tool
The usual trigger is a hard limit somewhere else: a 10 MB email attachment cap, a government portal that rejects anything over 5 MB, a university submission form, or a client whose inbox keeps bouncing your proposal.
The documents hitting those limits are rarely public. Uploading a signed contract to an unknown compression service to save four megabytes is a poor trade, so we built this tool to run entirely in your browser. The re-encoding happens on your own device through WebAssembly image and PDF libraries, and the compressed file is written straight back to you. No upload, no server-side copy, no account, and no watermark stamped across your output — which is how many free compressors monetise the same task.
Tips and common mistakes
- Text-only documents barely shrink; if a PDF is large and full of text, something else is inflating it, usually an embedded font set or a scanned cover page.
- Always view the compressed file at 100 per cent zoom before sending — softness that is invisible on a thumbnail is obvious in print.
- Compressing twice compounds the loss and rarely saves much the second time; go back to the original and use a stronger setting instead.
- If a portal rejects your file by a small margin, dropping the resolution slightly beats pushing the quality setting to its lowest level.
Quick start: using Compress PDF
- Add the PDF you want to shrink using the picker above.
- Pick a compression level — lighter settings preserve image detail, stronger ones cut the most size.
- Start the compression and give the browser a moment; image-heavy scans take the longest.
- Compare the reported before and after sizes to see what you gained.
- Download the result and check a page or two at full zoom before you send it on.
If the file is still too big, splitting it is often the better answer — Split PDF lets you send only the pages that matter.