Compress PDF Online – Reduce PDF Size Offline

How to Compress a PDF with This Tool

PDFs can get surprisingly large—especially ones with photos, scanned pages, or embedded graphics. This tool shrinks them down so they're easier to email, upload, or store. Everything happens in your browser; no files get uploaded.

Step-by-Step

1. Add your PDF
Drag your file into the area above, or click to browse. You'll see the original file size and page count right away.

2. Adjust your settings
Two main controls determine the output:

• DPI (dots per inch): Lower DPI means smaller files. 72 DPI works fine for on-screen reading. 150 DPI is a good balance for general use. 300 DPI preserves print quality.
• JPEG quality: Controls how much image data is kept. 60% gives strong compression with acceptable quality. 85% keeps things looking sharp with moderate size reduction.

3. Compress and download
Hit compress. The tool shows you the result: original size, compressed size, and the percentage reduction. Download when you're happy with it.

When You'd Want to Compress a PDF

• Email attachments: Gmail caps attachments at 25 MB. Outlook varies from 20-150 MB. Many corporate email servers set limits around 10-15 MB.
• Upload forms: Job applications, government portals, and court filing systems often have strict file size limits.
• Slow connections: Smaller files transfer faster, especially on mobile data.
• Storage: If you're archiving lots of PDFs, compression adds up to real space savings.
• Web hosting: Smaller PDFs on your website mean faster page loads for visitors.

Picking the Right Settings

There's always a trade-off between file size and visual quality. Here's a practical guide:

• Quick email share (screen reading only): 100-110 DPI, 60% quality
• General business use: 144 DPI, 70% quality
• Need to print it later: 200-300 DPI, 80-85% quality

Text-heavy documents compress well at almost any setting since text takes up very little space. The biggest savings come from image-heavy PDFs and scanned documents.

How the Compression Actually Works

The tool renders each page at your chosen DPI using PDF.js, converts the result to a JPEG at your selected quality level, then rebuilds the PDF with PDF-lib. This approach works well for most documents, but it's worth knowing that the output pages become image-based—interactive form fields and selectable text won't be preserved.

Privacy

Your files stay on your device. The compression runs entirely in your browser's memory using JavaScript. Nothing gets uploaded. Close the tab and everything's gone.

Tips

Start with 110–144 DPI and 60% quality. That usually gives a strong size reduction while keeping text readable. Adjust from there if you need better quality or smaller files.