Compress PDF Online
Reduce PDF file size to 1, 2, 5 or 10 MB — for tax filings, government portals or email. 4 quality levels, processed locally in your browser.
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PDF · Max size: 100.0MB
What Is PDF Compression?
PDF compression reduces file size by optimizing embedded images, removing duplicated resources, and more efficiently encoding data. A compressed PDF takes less disk space, loads faster via email and cloud storage, and meets requirements of services with attachment size limits. Convertilo performs compression locally in your browser, balancing file size and content quality.
About PDF Compression
Our tool reduces PDF file sizes by recompressing embedded JPEG images while keeping the vector text and graphics intact. For scanned documents and photo-heavy PDFs the Low preset can rasterize pages for maximum reduction. Everything runs locally — files never leave your device.
How compression works
- Walks the PDF to find embedded JPEG images and recompresses them via Canvas
- Keeps vector text and graphics lossless
- Reassembles the PDF via pdf-lib with compact object streams
- Bloat protection: if compression doesn't reduce the file we return the original
- Files never leave your browser
Technology Behind Our PDF Tools
Our PDF tools are built on two powerful JavaScript libraries that run entirely in your browser:
pdf-lib — A library for creating and modifying PDF documents. Used for merging, splitting, and page manipulation operations.
PDF.js — Mozilla's PDF rendering engine for parsing and displaying PDF content. Powers our PDF viewer and page export features.
Canvas API — Browser's built-in rendering API used for converting PDF pages to image formats (JPG, PNG, WebP) at any resolution.
All operations are performed locally — your documents are never uploaded to any server, ensuring complete confidentiality.
PDF compression advantages
Flexible quality levels
Choose between maximum compression and near-lossless output with four presets.
Page-by-page progress
See which page is being processed and the exact completion percentage.
Complete privacy
Documents stay in your browser — ideal for contracts and confidential files.
PDF compression FAQ
Does compression noticeably reduce quality?
It depends on the level. At 'High' quality, text and graphics remain sharp while the file is significantly lighter.
Is the text layer preserved?
Yes — on Medium, High and Maximum the vector text stays intact and only embedded images are recompressed. The Low preset may rasterize pages for maximum size reduction, in which case text selection becomes unavailable.
What is the maximum file size?
We recommend files up to 100 MB. Larger documents take longer to process.
Where are my documents stored?
Nowhere except your device. All compression runs locally in the browser.