Compress PDF
TL;DR: drop a PDF, pick a compression level and download a smaller file. Images inside the PDF are scaled down and re-encoded right in your browser; if the file is already optimal, we say so instead of giving you the same file back.
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Most heavy PDFs are heavy because of images: a scanned contract at 300 dpi, photos in a report or a presentation exported with full-size pictures. Email and online forms often limit attachments to a few megabytes. This tool lowers the resolution of those images to what is actually needed and re-encodes them, while the text stays sharp and selectable.
How to use it
- Add a PDF. Drag the file onto the box or choose it with the button.
- Pick a level. Recommended (110 dpi) suits email and sharing; Light (150 dpi) is for documents that will be printed; Strong (72 dpi) gives the smallest file for reading on screen.
- Compress. Press “Compress PDF”. You will see the size before and after and how many images were recompressed.
- Download the smaller file. If the saving is below 5%, the tool says the file is already optimal and does not offer a copy.
Which compression level to choose
| Level | Image resolution | Best for |
|---|---|---|
| Light | up to 150 dpi | Documents that will be printed, drawings with small details |
| Recommended | up to 110 dpi | Email, messengers, uploading to online forms |
| Strong | up to 72 dpi | Reading on screen, the smallest possible file |
The biggest savings come from scans and photo-heavy files: a page scanned at 300 dpi holds about 17 times more pixels than the same page at 72 dpi. A PDF made of text, tables and charts is already compact, so compression barely changes it; in that case the tool tells you the file is already optimal.
What is not changed: text, fonts, vector drawings, links and page layout. Black-and-white scans stored in CCITT or JBIG2 and images in CMYK are left as they are, so their colours do not shift.
At YuSMP Group we build websites and keep them fast, and heavy images and PDFs are the most common reason pages load slowly. If documents and images need optimising across a whole site, see our web development service or start with the page speed test.
FAQ
How do I reduce the size of a PDF?
Add the file, choose a compression level and press “Compress PDF”. The tool shows the new size and how much you saved, then you download the smaller file.
Is my PDF uploaded to a server?
No. Compression runs in your browser: the images are decoded and re-encoded on your device by the open-source pdf-lib library and the browser’s own image engine. The file is never sent anywhere.
How much smaller will my PDF get?
It depends on what is inside. Scans and photo-heavy PDFs often shrink by half or more on the Strong level. Files that are mostly text and vector graphics change little, and if the saving is under 5% we tell you the file is already optimal.
Will the text stay sharp and selectable?
Yes. Only images are changed. Text, fonts and vector graphics are kept as they are, so you can still select, copy and search the text.
Why does it say “the file is already optimised”?
Because the compressed copy would be less than 5% smaller than the original. Rather than give you the same file under a new name, we say it honestly. You can try the Strong level or keep the original.
Can I compress a password-protected PDF?
No: the content of a protected PDF is encrypted, so the images cannot be read. Remove the password in a PDF reader first, then add the file again.
Which level should I use for email?
Recommended (110 dpi) is a good default: the pages stay readable when printed at home and the file is usually small enough for email attachments.
Does compression remove pages or metadata?
No. All pages, links and the document title stay in place. Only the images inside the PDF are scaled down and re-encoded.