How to use Compress PDF
- 1
Add one or more PDFs
Drop up to 10 files of up to 50 MB each. Protected files ask for their password before they can be compressed.
- 2
Pick a compression level
Recommended (150 DPI images) suits most files; Light keeps 220 DPI for print, Strong drops to 96 DPI, Extreme flattens scans.
- 3
Fine-tune if needed
Advanced settings let you set the image resolution from 50 to 300 DPI, the JPEG quality, grayscale and metadata removal.
- 4
Compare and download
Each row shows the size before and after and the percentage saved. Save files one at a time, or grab them all in a single ZIP.
Limits and Pro
Up to 10 PDFs per batch, 50 MB per file and 200 pages per document, with no watermark.
Pro compresses files of up to 4 GB with up to 5,000 pages each, in batches of up to 500 PDFs. See Pro
About Compress PDF
Compress PDF returns a PDF with the same pages, text and layout, only lighter. The savings come mostly from the photos and scans inside the file: each image is measured at the size it is drawn on the page, scaled down if its resolution is higher than the level you chose, and re-encoded as JPEG or lossless Flate, whichever is smaller. Fonts, text and vector drawings are not touched, so words stay sharp, selectable and searchable. On top of that, every level drops page thumbnails, duplicate images and fonts, unused objects and editing data left by design apps, removes author and app metadata (the document title is kept), and a final qpdf pass repacks the file structure losslessly.
If none of that makes a file smaller, you get your original back rather than a heavier copy. The usual reasons for running it are email attachment caps of 20–25 MB, upload portals for job applications, visas or court filings that accept only a few megabytes, and archives of scanned paperwork.
Limits worth knowing: images already stored as JPEG 2000, JBIG2 or CCITT fax, CMYK photos and one-bit scans are left as they are. Text-only PDFs have little to remove, so expect 10–40% or no change. The Extreme level turns every page into a single JPEG image, which shrinks scans the most but makes text unselectable and removes links and form fields. A password on the input is not carried over to the compressed copy.
Privacy
Images are re-encoded by pdf-lib and your browser's own JPEG encoder inside a Web Worker, and the lossless pass uses qpdf compiled to WebAssembly (about 1.3 MB, fetched from this site the first time you compress). The Extreme level renders pages with PDF.js in this tab. At no point is the PDF, or anything read from it, sent over the network.
Features
Text stays selectable
Only images are recompressed. Fonts, text and vector drawings are untouched, so nothing gets blurry.
Smart image downsampling
Images are measured as they appear on the page and reduced only when their resolution is higher than needed.
Never bigger than before
If a file is already optimized, you get your original back instead of a larger copy.
Batch compression
Compress several PDFs in one go and download them together in a single ZIP archive.
Extreme mode for scans
Flattens each page to an optimized image — the smallest possible size for scanned paperwork.
PDF compression levels explained
Light keeps images at up to 220 DPI with high JPEG quality, which suits documents you plan to print. Recommended targets 150 DPI, crisp on screens and in most office prints, and gives the best balance between size and quality. Strong goes down to 96 DPI with heavier JPEG compression for the smallest file that still keeps real text.
Extreme works differently: it renders every page at 110 DPI as one JPEG image. It is meant for scanned paperwork, where the pages are pictures anyway, but text can no longer be selected or searched and links and form fields disappear. Open Advanced settings for precise control over resolution, quality and grayscale.