Compress PDF
Reduce your PDF size by re-rendering at optimized quality. Choose Low/Medium/High compression. All processing in your browser — no uploads.
Click or drag a PDF here
How to use Compress PDF
Reduce PDF file size significantly without noticeable quality loss — entirely in your browser using advanced compression algorithms. Smaller PDFs load faster, consume less storage, and stay within email attachment limits. This tool recompresses images and removes redundant metadata while preserving text crispness, vector graphics, and document structure.
- Upload your PDF by clicking or dragging it to the tool.
- Select a compression level: light (minimal quality loss), balanced, or maximum compression.
- Preview the estimated output size and quality comparison.
- Click "Compress PDF" and wait for the browser to process the file.
- Download the compressed PDF and verify the quality meets your needs.
Your data never leaves your device — 100% private processing.
What PDF compression actually does
Most PDFs contain embedded images at full resolution, even when only screen viewing is intended. Compression downsamples and re-encodes images (JPEG for photographs, PNG for graphics with transparency) at a lower quality setting. It also deduplicates identical embedded objects, strips metadata like creation timestamps and author information, removes embedded thumbnails, and applies DEFLATE or JBIG2 stream compression to content streams and font data.
Choosing the right compression level
Light compression (high quality) targets screen viewing at 150 DPI and removes only redundant metadata — file size reduction of 15–40% for typical office documents. Balanced compression resamples images to 96 DPI and applies moderate JPEG quality — typical reduction 40–70%. Maximum compression drops images to 72 DPI with aggressive JPEG encoding — 70–90% reduction, appropriate only for archiving or sharing where print quality is not required. Vector text and diagrams are never degraded by any compression mode.
Scanned vs. native PDFs
Scanned PDFs are essentially image containers — every page is a single raster image. Compression has the highest impact here, potentially shrinking a 10 MB scanned document to under 1 MB on maximum settings. Native PDFs (created by Word, LaTeX, or design tools) contain vector text which compresses differently; the file size reduction is smaller but text quality is never compromised. For scanned documents that need to remain searchable, apply OCR before compressing.
Glossary
- DPI
- Dots per inch — a measure of image resolution. Higher DPI means more detail but larger file size.
- DEFLATE
- A lossless data compression algorithm used in PDF content streams to reduce file size without quality loss.
- JBIG2
- A compression standard optimized for bitonal (black and white) images, widely used for scanned documents.
- Downsampling
- Reducing the pixel resolution of an embedded image to lower file size, typically applied to photos in PDFs.
Related reading
Frequently Asked Questions
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Why use Compress PDF?
- Process files entirely in your browser — nothing is uploaded to any server
- Works on any device: desktop, tablet, or mobile
- No watermarks, no account required, completely free
- Handles multi-page PDFs without file size penalties
Common use cases
- Merge contracts before emailing to a client
- Split a large PDF report into separate deliverables
- Compress PDFs before attaching to email
- Remove a password from a personal PDF document
- Convert scanned images into searchable PDFs
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