Compress PDF

Recommended downsamples pictures so their longest side is at most 1600 pixels and re-encodes them as JPEG at 75% quality. Strongest uses 1000 pixels and 50% quality. Light leaves every picture's pixels exactly as they were and only tidies the file: it compresses streams that were stored uncompressed, removes objects that nothing refers to any more, and writes a compact file structure. In every setting a picture is only replaced when the new version is actually smaller.

As soon as a file is ready, this device works out the size each level would give. Light's is exact: the tool runs Light itself, which takes a moment, and a file with no picture to re-encode gets that exact size at every level. For Recommended and Strongest it re-encodes a sample of the pictures - the largest, and one of each kind the largest do not stand for - and reckons the others from that sample, so it shows a range. Where the pictures differ too much for a useful range, it says the size is known only after compressing. The size in the result, after compressing, is exact. All of this happens on this device.

Files that are mostly text or vector drawings have little to compress. Pictures that are already small JPEGs stay as they are. Some picture types are always left unchanged by this tool: JPEG 2000, CCITT fax and JBIG2 scans, CMYK JPEGs, stencil masks, pictures with colour-key masking, pictures drawn inline in the page content, and pictures above 30 megapixels. If nothing can be saved, the tool says so and hands back the original file rather than a larger one.

No. Only picture data is re-encoded. Page content, fonts, form fields, bookmarks, links and annotations are kept. Transparency (soft masks) on pictures is kept too. Existing metadata such as title, author and keywords is not removed: Clean PDF metadata removes it.

No. The page loads a PDF engine into your browser and every operation runs on your device. You can check this yourself in the browser's network panel: after the page has loaded there are no upload requests. Closing the tab discards the file.

No. These basic tools are free, have no page or file limits set by us, and never add a watermark. The practical limit is your device's memory.

Encrypted PDFs cannot be processed here. Remove the password first, then use this tool.

Nothing you open or type. While the tab is open, the tool pages keep a short list of the steps taken in it, in the tab's session storage: the step (page opened, started, succeeded, first success, used again or failed), the tool's name, the time, how many files were used and, for a failure, an error code; never a file name, the contents of a file or your text. It holds at most the latest 200 steps, and the browser deletes it when the tab closes. The page never sends it. Where a Report a problem button is shown, you can attach the last 20 steps to your report; nothing is attached unless you tick that box. In local storage the page keeps only choices you made: a Light or Dark theme until you choose System again, the language you picked with the EN / 中文 switch if it differs from your browser's language, and this tool in your recently used list if you switched that list on at the tools page.