Compress PDF
Reduce PDF file size with lossless clean-up or stronger compression.
How to use Compress PDF
- Add the PDF you want to make smaller.
- Choose a level: Low is lossless, Recommended re-renders pages, High pushes the size down hardest.
- Press Compress and wait — larger documents take longer because every page is processed.
- Compare the reported before and after sizes, then download if the saving is worth it.
How Compress PDF works
Two very different things get called “PDF compression”. The first is a lossless clean-up: the file is rewritten more efficiently and unused objects are dropped, with nothing re-encoded. Text stays selectable and images keep their quality, but the saving is modest.
The second re-renders every page as an image and rebuilds the document around those pictures. Recommended draws each page at 108 dpi, High at 79 dpi, and both store the result as JPEG. On scans and image-heavy files this can cut the size dramatically, which is why most online compressors do it. The cost is real: the text layer is gone, so the document is no longer searchable, selectable or readable by a screen reader. This tool labels that clearly rather than hiding it.
Which level to choose follows from what the document is made of, not from how large it is. A scan has no text layer to begin with — it is already pictures of pages — so the rasterising levels take almost nothing away from it and usually save the most. A file produced by a word processor or a spreadsheet is the opposite case: its text and vector graphics are already compact and already searchable, so rasterising gives up the most and gains the least. Low is the right answer there even though it saves less.
That is also why a compressed file can come out larger than the original. A page of real text occupies very little; a photograph of that same page at 108 dpi often occupies more. The tool compares the two sizes and tells you when there was nothing to gain, rather than handing back a worse file and calling it a saving.
After compressing you get the original size, the new size and the percentage saved. If the result is not actually smaller, the tool says so instead of pretending otherwise.
Frequently asked questions
Are my files uploaded to a server?
No. This tool runs entirely inside your browser — the file is read from disk by the page and never transmitted. It keeps working even if you disconnect after the page has loaded.
Which compression level should I choose?
Judge it by what the document contains. Scans and image-heavy files gain the most from Recommended and lose nothing meaningful, because there was no text layer to lose. Word-processor and spreadsheet exports are the reverse: Low is lossless and keeps text selectable, and although it saves less, rasterising such a file costs far more than it returns. Use High only when the smallest possible file matters more than fidelity.
Why did my file get bigger?
Two different reasons. At Low, some PDFs are already packed efficiently and a lossless rewrite adds a little overhead instead of removing it. At Recommended or High the cause is usually the opposite of what people expect: rasterising a text or vector document replaces compact instructions with a JPEG photograph of each page, and that photograph can easily be larger than the text it replaced. Either way both sizes are reported, so you can simply keep your original.
Will compression affect printing?
Page dimensions are preserved exactly, so the document still prints at the right physical size. Resolution is the thing to watch: Recommended renders pages at 108 dpi and High at 79 dpi, both well below what printing on paper normally wants, and at High the softness is usually visible. For anything that will be printed, prefer Low — or Recommended only when the source was already a scan.
Can I use a password-protected PDF?
A PDF that merely declares encryption with an empty owner password usually opens fine. One that genuinely requires a password to be read cannot be processed, and the tool says so instead of failing silently — remove the protection first, then come back.
Further reading
- PDF Compression: What Actually Happens to Your File?Where the bytes in a PDF really go, why scans shrink dramatically and text documents barely move, and what you trade away for a smaller file.
- How to Compress a PDF for an Email Size LimitWhy a 25 MB limit is really about 18 MB of file, the order to try things in, and the point at which compressing further stops being the right answer.
- Why Browser-Based PDF Tools Can Reduce Unnecessary File UploadsHow local processing differs from the traditional upload-and-download model, what it genuinely protects against, and what it does not.