Reduce your PDF file size online for free. Pick a compression level, see the before/after size, and download — everything happens in your browser, so your files never leave your device.
1 = Maximum compression (smallest file) · 2 = Balanced · 3 = High quality (larger file)
Note: pages are rebuilt as optimized images, so text won't stay selectable. Best for scanned PDFs, forms, and image-heavy documents.
Part of the PDF Tools collection — browse all related free tools.
Most PDFs are large because of high-resolution images inside them. This tool renders each page and rebuilds the document with sensibly sized, JPEG-optimized images — the same trick professional tools use, done entirely on your device.
Upload your PDF above, choose a compression level with the quality slider, and click Compress. The tool rebuilds your PDF with optimized images right in your browser and shows the before/after file size.
Yes. Everything happens locally in your browser — your PDF is never uploaded to any server, so your documents stay private.
Higher compression means smaller size but slightly softer images. Use the quality slider to find the balance you need — the result shows the exact size before you download.
Yes. It is 100% free with no signup and no daily limits, unlike many tools that cap free use.
No — real PDF text is stored as vector glyphs, not pixels, so compression leaves it perfectly sharp and only targets images. The exception is scanned pages, which are images of text; those can soften at aggressive settings, so use lighter compression for scans you need to read closely.
The file was probably already optimized, or it's dominated by high-resolution scanned images. Try a stronger compression level, or split out pages you don't need — a single heavy page with full-page scans can account for most of the file size.
Yes — compression runs entirely in your browser, so the file never uploads to any server. If you want extra assurance, disconnect from the internet while using it; everything keeps working, which proves nothing leaves your device.
A PDF is a container holding text, vector graphics, embedded fonts, images, and metadata — and the images are almost always the bulk of the size. Compression attacks the heavy parts: downsampling images (fewer pixels), re-encoding them at lower quality, subsetting fonts (keeping only the glyphs actually used), merging duplicate objects, and stripping metadata and thumbnails. Everything here runs locally in your browser — the file never uploads anywhere.
The method, in order: scan every image object and re-encode it at the target resolution and quality (e.g. 300 DPI → 150 DPI, JPEG quality 70 for screen use); replace full font embeds with subsets; drop document metadata, embedded thumbnails, and unused objects; then rewrite the file with tighter object streams. Text and vector graphics are already tiny, so they're left untouched.
Worked example: an 8.4 MB scanned report. Its images weigh ~7.9 MB; downsampling to 150 DPI at quality 70 shrinks them to ~1.8 MB; font subsetting saves another ~0.3 MB; metadata cleanup takes ~0.2 MB. Final size ≈ 2.1 MB — a 75% reduction — still crisp on screen and perfectly readable when printed at normal sizes.
Practical tips: choose screen quality for email and uploads, print quality when the document will be professionally printed; OCR text layers survive compression untouched, so searchable PDFs stay searchable. Limitation: an already-optimized PDF barely shrinks further, and scanned pages can never compress as small as real text — for the tiniest file, retype or OCR rather than re-compress.
Choosing the right compression level: think in DPI targets, not percentages. 150 DPI is the sweet spot for screen viewing and email — text stays crisp, photos look fine, files shrink dramatically. 300 DPI preserves print quality for documents that will be professionally printed; going below 150 risks visibly soft images, above 300 wastes bytes almost nobody can see. Two PDF features interact with compression: linearized ("fast web view") PDFs reorganize the file so page one displays before the rest downloads — worth enabling for large documents hosted online; and PDF/A archival files embed everything (fonts, color profiles) for century-long readability, which makes them inherently larger and poor compression candidates. If a compressed file must remain legally archivable, convert to PDF/A after compressing, not before. And for scanned documents, running OCR before compression lets you downsample images more aggressively, since the searchable text layer carries the information.