Compress PDF
Reduce PDF file size while keeping your document readable.
Tap to choose a file
Compress PDF shrinks a file's size by re-optimizing the images and internal structure inside it, using the Stirling-PDF engine that also powers our other PDF conversions. Your file uploads once, gets processed on our server at the compression level you pick — light, balanced, or strong — and is deleted automatically about an hour later. Because compression works on the images inside the file, a scanned or photo-heavy PDF usually shrinks far more than one made mostly of typed text.
How it works
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Choose or drop the PDF you want to shrink.
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Pick a compression level.
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Click Compress PDF.
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Download the smaller file.
What you can use it for
- Shrinking a scanned assignment below a school portal's upload size limit before submitting it.
- Getting a photo-heavy lab report small enough to attach to an email without bouncing.
- Reducing a portfolio PDF full of design images so it uploads quickly to a job application form.
- Compressing lecture slides exported with large embedded images before sharing them in a group chat.
Frequently asked questions
How much smaller will my PDF get?
It depends on the content. Scanned and image-heavy PDFs often shrink by 50% or more; text-only PDFs are already small and compress less.
What happens to my file after compression?
It's processed on our server and automatically deleted within 1 hour. We never read or share your documents.
What's the maximum file size?
100 MB per PDF.
What does the grayscale option actually do?
It converts every embedded color image to grayscale before recompressing, which can shrink colorful scans further than color compression alone. That conversion is permanent, so the output file loses its color entirely. Keep a copy of the original PDF if you might need the color version again.
Which compression level should I pick?
Light keeps the most detail and suits documents with diagrams or photos you'll print. Balanced works for most everyday PDFs. Strong gives the smallest file and suits text-heavy documents you'll only read on screen.
If I want a smaller file, should I use Split PDF or Organize PDF instead?
Those tools change which pages are in the file. Compress PDF keeps every page but re-encodes the content so it takes up less space.
My PDF barely got smaller — why?
PDFs exported from Word or PowerPoint without large embedded images are often already near their practical minimum size. Higher compression levels mostly help image-heavy or scanned files.
Good to know
- Text-only PDFs are already compact, so compression may only save a few percent no matter which level you choose.
- Strong compression noticeably reduces image quality — use Light if the PDF contains photos or diagrams that need to stay sharp.
- Grayscale conversion is one-way; keep a copy of the original if you might need the color version later.
- Files are capped at 100 MB, and the tool compresses one PDF per run — process multiple files one at a time.