Compress a PDF in your browser

That depends on the images in it. A PDF of high-resolution photos or scans can shrink a lot. The tool only changes images that are sharper than the level you chose, or that get smaller when saved as JPEG. If the result is not smaller, the tool says so and offers nothing to download.

Text, fonts and vector drawings are already compact, and this tool leaves them alone. It only compresses page data that was stored uncompressed and removes objects that nothing uses. A PDF without large images usually shrinks by 10% or less, often much less.

Yes, at the Light, Medium and Strong levels, because only the images change. The fourth option, Rasterize pages, turns every page into one JPEG image. That copy has no selectable or searchable text, and its links and form fields stop working. Use it only for scans, or for files where only the look matters.

It handles JPEG images, and uncompressed or Flate-compressed images in RGB or grayscale with 8 bits per channel. That covers most photos and scans. It leaves CMYK images, JPEG 2000, JBIG2 and fax-style black-and-white images, image masks and images over 60 megapixels as they are, and it reports how many it skipped. Images with transparency keep their transparency mask at the original size.

It reads the page content to find how large each image is drawn, then lowers the image to the chosen dpi at that size. It never enlarges an image. When it can't find where an image is drawn, for example inside an annotation, it assumes the image fills a whole page.

The tool saves images as JPEG, which loses some detail. Light keeps the most. Screenshots and diagrams with sharp edges show JPEG artifacts sooner than photos do. Check the result before you delete the original.

Yes, at the three image levels. Apart from the images, the PDF keeps its structure. Digital signatures become invalid, because the file changes.

Files can be up to 100 MB. Your device has to hold the file and the result in memory, so a phone with little memory may fail on large files before that limit.

No. The tool does not support encrypted or password-protected PDFs. Remove the password in the app that created the file, then try again.

No. The page and its code load from quireapps.com. After that, your browser reads the file and does all the work in this tab. Nothing is sent to a server, and the page has no analytics or tracking. To check, open your browser's developer tools and watch the Network tab while you use the tool.

It is free, and you don't need an account. The tool adds no watermark and has no daily limit.

Testing covers Chrome. The tool uses features that current versions of Edge, Firefox (105 or later) and Safari (16.4 or later) also have, but those browsers have had less testing here.