Reduce PDF File Size — Free PDF Compressor
Shrink PDF file size for email and upload limits: compress images and streams locally in your browser. Free, no watermark, no signup, no page limits.
Portal upload limits and email attachment caps meet scanned PDFs — and the scan always wins. This compressor reduces PDF size by re-encoding embedded images and streams at sensible quality levels, typically cutting scanned documents by half or more while keeping text crisp.
Compression runs locally in your browser. Contracts, medical records, and ID scans never leave your device, and the output carries no watermark or page-count restrictions.
100% in-browser · no upload · no signup · nothing you paste or drop here leaves your device
PDF Compress
Smart compression: auto-detects PDF type and picks the best strategy — 100% browser-based
Smart compression auto-detects PDF type: image-heavy PDFs use JPEG re-encoding for maximum reduction, while text-heavy PDFs use lossless structure optimization. All processing happens in your browser.
Why one PDF compresses a lot and another barely — illustrated
A PDF is a bag of numbered objects: page dictionaries, font programs, image XObjects and content streams. Text-based PDFs are already lean, so this tool uses a lossless rebuild: it strips document metadata, removes duplicated objects, re-packs the streams with FlateDecode (zlib) and groups objects into object streams with a compressed cross-reference stream. Image-heavy PDFs (scans, photos) are different: their bulk is raster data, so a lossy path re-renders every page to a fresh JPEG at the chosen quality and DPI, discarding the original image and text streams. The tool auto-detects which family your file belongs to by measuring bytes-per-page and counting image operators in the page content.
Top: text PDFs gain only a few percent from a lossless restructure. Bottom: image PDFs can lose 50–75% because their bulk is re-encoded JPEG raster.
A 12.4 MB, 40-page scanned agreement with photos, compressed at the Medium level (70% quality, 120 DPI, 0.85 scale).
- Auto-detect:At ~310 KB per page the file is flagged image-heavy and routed to the lossy pipeline
- Re-render:Each page is drawn at 0.85 × 120/72 ≈ 1.42× scale, then JPEG-encoded at 70% quality
- Re-embed:The fresh JPEG XObjects are placed on same-size pages — original streams are dropped
- Result:Output lands at ≈ 3.9 MB (~68% smaller); a 450 KB text PDF by contrast only loses ~8% losslessly
About this reduce PDF file size
This page covers compress pdf online free, make pdf smaller, shrink pdf file size for email, pdf compressor no loss — all the same underlying task as reduce PDF file size. The tool above is FreeToolHub's pdf compress embedded in full: every feature works right here, and nothing you process is uploaded to any server.
Frequently asked questions
How do I make a PDF smaller without losing quality?
Most PDF bulk is high-resolution scanned images, not text. Re-encoding those images at screen-appropriate resolution and JPEG quality typically halves the size with no visible difference on screen. Text-heavy PDFs compress less — their size is mostly structure, and they are already efficient.
Is it safe to compress confidential PDFs here?
Yes — the compression pipeline runs entirely in your browser using JavaScript and WebAssembly. Unlike online PDF services that upload documents to their servers, this tool never transmits your file, which matters for contracts, medical records, and identity documents.