Compress PDF Online — Reduce PDF File Size
Reduce PDF file size while preserving document quality. Choose Smart (automatic), Low, Medium, or High compression — your PDF is processed locally in your browser, no uploads, no sign-up.
Upload a PDF file
Click or drag & drop a PDF here
Supports PDF files
Your file is processed locally in your browser and is never uploaded to our server.
Compress PDF Online in Your Browser
This tool reduces PDF file size in two safe steps. First, a lossless pass cleans the file structure: uncompressed streams are re-encoded, unreachable objects are dropped, duplicate images are shared and stale metadata is removed. Then a lossy pass intelligently optimizes large images: JPEG photos are recompressed and images displayed at excessive resolution are downsampled to a sensible DPI — the aspect ratio and the exact page layout never change.
Everything runs locally in your browser inside a Web Worker: the file is analyzed, optimized and rewritten without ever being uploaded anywhere.
How to Compress a PDF Online
- 1
Upload your PDF file.
- 2
Choose Smart (recommended), Low, Medium or High compression — Smart automatically picks the best strategy for your PDF.
- 3
Click "Compress PDF" — the tool optimizes the document structure and its images, then verifies the result.
- 4
Download the smaller PDF — if nothing could be saved, your original file is kept.
What This Compressor Does
Two-stage optimization: a lossless pass re-encodes uncompressed and legacy-encoded streams, removes objects nothing references and stores byte-identical images only once; a lossy pass recompresses JPEG images and downsamples oversized images based on their actual display size.
Safety first: text, fonts and vector graphics stay untouched; links, annotations, bookmarks and form fields survive the rewrite; and an image is only replaced when the re-encode is genuinely smaller. Digitally signed PDFs are detected and left unchanged.
Verified output: after rewriting, the result is re-parsed and checked page by page (count, size, rotation, links, forms) before it is offered for download. If the optimized file would not be smaller, the original is preserved.
Private by Design — Your File Never Leaves the Browser
Analysis, optimization and rewriting all happen locally in your browser using Web Workers. Your PDF is never uploaded to a server, and the tool keeps working even if you go offline after the page has loaded.
Frequently Asked Questions
Will the compression reduce the quality of my PDF?
Low keeps images at high quality. Medium (recommended) recompresses large JPEG photos and downsamples images displayed at excessive resolution — text stays sharp and photos remain clear. High trades more quality for the smallest possible file. At every level, text remains real, selectable text and the page layout never changes.
Why did my file not get smaller?
Some PDFs are already tightly packed — for example files produced by modern PDF software with compressed streams and already-efficient images. When no reduction is possible without sacrificing quality, the tool keeps your original file instead of returning a larger one.
What happens with password-protected PDFs?
Encrypted PDFs cannot be processed safely in the browser. The tool detects them and shows a message instead of touching the file.
What happens with digitally signed PDFs?
Rewriting a signed PDF would invalidate its signature. The tool detects signature fields and leaves such documents untouched.
Does my file get uploaded anywhere?
No. All processing happens locally in your browser inside a Web Worker. Your file never leaves your device.
Can I still use other PDF tools after compressing?
Yes. The compressed PDF is a normal PDF — merge it, split it, rotate pages or convert pages to images with the other tools on this site.
Found an issue with this tool?
Report a problem