🗜️ Compress PDF ☆

Overview

Free PDF Compressor is a free online tool that reduces the file size of your PDF documents while preserving visual quality. Choose from multiple compression levels, low for minimal quality loss, medium for balanced output, or high for maximum file size reduction. The tool optimizes embedded images, removes redundant metadata, and compresses fonts without altering the document layout. You can compress a 50 MB report down to a fraction of its original size, making it easy to email, upload, or archive. There is no sign-up, no watermark, and no daily limit on how many files you compress. Everything runs securely in your browser. Your PDF is never uploaded to any server. The tool supports password-protected PDFs and maintains all text, links, annotations, and form fields after compression. It is perfect for reducing email attachment sizes, optimizing PDFs for web publishing, freeing up storage space, or preparing documents for online submission portals with strict file size limits. Works on all modern browsers across desktop and mobile devices.

How PDF compression works

The compressor rewrites the PDF structure instead of re-rendering pages. It downsamples oversized embedded images to sensible screen or print resolutions, re-encodes them with efficient compression, removes duplicate objects and unused metadata, and streamlines fonts, while the text layer, page geometry and reading order stay untouched. Because nothing is rasterized, text remains selectable and searchable after compression, and links, annotations and form fields keep working. The savings come mostly from images, which is why scanned documents shrink dramatically while text-only PDFs change very little.

Specifications and compatibility

Property	Compress PDF behavior
Input format	PDF 1.0-2.0, including scanned and password-protected files
Compression levels	Low, medium and high, trading image quality for size
Preserved	Text layer, links, annotations, form fields, page order
Typical savings	Scans and image-heavy reports: 50-90%; text-only files: small
Processing	100% client-side (JavaScript + pdf-lib), no upload
Network requests	None after the page loads
Limits	No tool limit: bounded only by device memory
Cost	Free, no account, no watermark, no daily cap

Privacy: documents never leave your device

Contracts, medical records and financial statements should not be uploaded to a stranger server just to lose a few megabytes. This tool reads the file with the File API, compresses it in browser memory and hands it back as a download. Nothing is transmitted, stored or logged, and the tab closing clears everything. You can confirm it in the developer tools Network panel: compressing a document generates no traffic.

Choosing the right compression level

• Use low compression for print-quality archives where detail matters most.
• Use medium for email attachments, usually the best size-to-quality balance.
• Use high for upload portals with strict limits, where legibility beats fidelity.
• Compare the before/after preview before sending anything important.
• Keep the original until you have verified the compressed copy.

Need other PDF operations? Browse all PDF tools to merge, split, rotate, protect or convert documents.

Compression levers: images, fonts and structure

PDF compression is mostly about deciding where to spend quality, because the format itself is already efficient. Images dominate the file size in almost every real document, so the biggest win is downsampling: reducing a 300 DPI photo to 150 DPI for screen viewing cuts its pixel count to a quarter, and re-encoding at a moderate JPEG quality removes more. Scanned documents are a special case. They are one large image per page, so they compress dramatically, and a 600 DPI colour scan can often drop to a few percent of its size with no visible loss at reading zoom. Text and vector graphics compress differently: object streams and cross-reference streams remove repetition in the file structure, and font subsetting keeps only the glyphs actually used instead of embedding a full typeface. Removing metadata such as editing history, thumbnails and private application data saves a little space and is often desirable for privacy. Two cautions are worth stating. First, compression is not free: aggressive downsampling makes small text in scanned pages blurry, which matters for contracts and invoices. Second, linearization, arranging the file for fast web viewing, does not reduce size and may slightly increase it, but it makes the first page appear before the whole download finishes. Everything is processed locally in your browser.