Compress PDF – Reduce PDF File Size Free Online

Your PDF file is never uploaded to any server. This tool works entirely in your browser using PDF.js to parse and render PDF pages, and Canvas API to re-encode them at a lower quality. All processing happens locally on your device, making it completely safe for confidential documents, legal contracts, medical records and personal files.

Compression results depend on the content of your PDF. PDFs with many high-resolution images compress the most (60-90% reduction). PDFs that are mostly text compress less (20-40% reduction) because text data itself is already compact. The Extreme setting can reduce image-heavy PDFs by up to 90%.

Grayscale mode converts all pages to black and white before compression. Color information takes up significant space in PDF files, so removing it can dramatically reduce file size — often by an additional 30-50% compared to color compression at the same quality level. Grayscale is ideal for scanned documents, text-only PDFs and reports where color is not important.

Render Scale controls the resolution at which each PDF page is rendered before re-encoding. Standard (1.0x) preserves the original page dimensions. High (1.2x) renders at higher resolution for slightly better quality. Compact (0.8x) and Minimal (0.6x) render at lower resolution, producing much smaller files but with reduced sharpness — good for small-screen viewing or archiving.

Yes, even at High and Extreme compression levels, text in most PDFs remains readable. The quality reduction mainly affects photographic images and detailed graphics. For documents that are primarily text, Medium compression (quality 70-80%) produces virtually no visible difference while reducing file size significantly. Always preview your compressed PDF before sharing to verify quality.