How to Compress a PDF Online (Free, No Upload)

Hitting email attachment limits or a slow upload form? A quick lossless pass over your PDF's internal structure can cut real size with zero quality loss — and it never leaves your browser.

Use the free tool: Compress PDF — no uploads, files stay in your browser.

Before you start

You only need the PDF and a modern browser. Compression here is lossless: it rewrites the PDF's structure and enables object streams. Text, images, and layout come out pixel-identical.

Steps

1. Open the PDF Compressor.

2. Add your PDF — drag and drop, or click to choose. You'll see your file's input size ("Selected: X").

3. The mode is Optimize structure (lossless) — the safe default that never degrades quality.

4. Click Compress PDF and wait while it processes on your device.

5. Check the result: it shows output size and your savings percentage ("Output: Y • Savings: Z%").

6. Download compressed.pdf.

When it works best (and when it doesn't)

• Big wins: PDFs exported from Word, InDesign, or report generators often carry redundant internal objects — these shrink well.
• Small wins: already-optimized PDFs and scanned documents (mostly images) won't shrink much structurally.
• Image-heavy PDF barely shrinking? The images are the bulk. Compress the images first (image compression tips), then rebuild or compress the PDF.

Troubleshooting

• Savings near 0%? Your PDF is probably already optimized — that's good news, not a failure. If images dominate the file, see above.
• Need a specific target size? Lossless compression can't promise an exact size. For email limits, combine this with deleting unneeded pages (Remove PDF Pages).
• Download didn't start? Check that your browser isn't blocking downloads for this site.

Next steps:

• Lossless vs lossy compression, explained
• Delete unneeded pages first
• Image compression tips