Compress PDF
Shrink a PDF by rebuilding it with compressed object streams — with honest before-and-after sizes.
Many PDFs carry bloat: unused objects and unpacked structure left by the app that made them. This tool rebuilds the file with compressed object streams and drops the dead weight, then shows you the true before-and-after sizes. It does not secretly degrade images — and it says so up front.
Your file never leaves your browser — optimization happens on your device.
How to use this calculator
- Choose the PDF to optimize — it processes immediately.
- Compare the original and optimized sizes in the result cards.
- Keep the downloaded file if it is smaller; otherwise keep your original.
The formula
Savings = (1 − optimized size ÷ original size) × 100, rounded to one decimal. A 2,400,000-byte file rebuilt to 1,800,000 bytes saves exactly 25.0%.
Worked example
If a 2.40 MB PDF rebuilds to 1.80 MB, the tool reports '25% smaller' — the same math it applies to your real file when you run it.
Frequently Asked Questions
How much smaller will my PDF get?
It depends entirely on how the file was built. PDFs exported by office apps and design tools often shrink 10-40%. A PDF that is already efficiently built may not shrink at all — the tool shows the real numbers either way instead of promising a percentage.
Why did my scanned PDF barely shrink?
A scan is usually one big image per page, and this tool deliberately does not recompress images (that is what would blur your scan). The images dominate the file size, so rebuilding the structure around them saves little. That honesty is the trade-off for keeping full quality.
Does compression reduce quality?
No. Text, vector graphics, and images are copied unchanged. Only the container structure — object streams and cross-references — is packed more efficiently, which is lossless.
Is my file uploaded to compress it?
No. The rebuild happens in your browser with pdf-lib. Your document never crosses the network, which matters for the contracts and statements people usually want to shrink for email.
What if the optimized file comes out larger?
It can happen with tiny, already-tight PDFs, because the rebuilt structure has a small fixed overhead. The result panel tells you honestly if the file grew — in that case, just keep your original.