Compress PDF
Compress PDF files online for free by recompressing embedded images. Shrink large, image-heavy PDFs by up to 80% without touching text, 100% private.
About This Tool
Reduce the file size of your PDF documents by recompressing embedded images at a lower quality level. This is the most effective way to shrink PDFs that contain photographs, scanned pages, or other image-heavy content. Text, vector graphics, and formatting remain unchanged, only raster images within the PDF are re-encoded. Processing happens entirely in your browser, ensuring your documents remain private.
How To Use
- Upload one or more PDF files by dragging them into the drop zone.
- Adjust the image quality slider, lower means smaller but less sharp images.
- Click "Compress" to process your files.
- Download your compressed PDFs and compare file sizes.
How It Works
PDF compression in the browser works by targeting the largest contributors to file size: embedded raster images. The tool loads your PDF using pdf-lib, identifies all embedded image objects, decodes each one, re-encodes it as a JPEG at your chosen quality level using the Canvas API, and replaces the original image data in the PDF.
This approach is highly effective for PDFs created from scanned documents, photo-heavy reports, or presentations with large images. A 20MB scanned PDF can often be reduced to 3-5MB at 60% quality with no visible difference when viewed on screen.
Text, vector graphics, fonts, and other non-image content are not modified, compression only affects raster images. If your PDF contains mostly text and few images, the size reduction will be minimal. The tool processes each PDF in a Web Worker, keeping your browser responsive. Multiple files are processed sequentially to manage memory usage.
Frequently Asked Questions
Will text quality be affected?
No. Only embedded raster images are recompressed. Text, vector graphics, fonts, annotations, and all other PDF content remain completely unchanged. Your documents stay perfectly readable.
How much smaller will my PDF be?
It depends on the content. Image-heavy PDFs (scans, photos) can shrink by 50-80% at 60% quality. Text-only PDFs may barely change size since there are few images to compress.
What quality level should I choose?
For most purposes, 60% offers an excellent balance between size and quality. For archival or print use, try 80-90%. For maximum compression where visual quality is less important, go as low as 20-30%.
Can I compress password-protected PDFs?
Not directly. Remove the password first using our Remove PDF Password tool. Once unprotected, you can compress the PDF and optionally re-protect it using a third-party tool.
Is lossless PDF compression possible?
Browser-based lossless PDF compression is very limited. Our tool focuses on lossy image recompression, which gives the most significant file size reductions. The tradeoff is a slight reduction in image sharpness.
Are my PDFs uploaded anywhere?
No. All compression happens locally in your browser using pdf-lib and the Canvas API. Your documents are never uploaded to any server and remain entirely on your device throughout the process.