Compress PDF (Smart) — Private, In-Browser
This tool reduces PDF file size directly in your browser—no uploads, no servers. It combines pdf.js for rendering pages, pdf-lib for rebuilding PDFs, and MozJPEG (WASM) for high-quality JPEG compression. Scanned/image-heavy pages are aggressively shrunk, while text/vector pages can pass through crisp.
Why use this PDF compressor?
- 100% private: Processing happens locally in your browser.
- Smaller files by default: Sensible, aggressive defaults (quality/DPI) target meaningful size savings.
- Keeps text crisp: Text/vector pages can skip rasterization for sharp results.
- MozJPEG (WASM): Industry-grade JPEG optimization compiled to WebAssembly for better shrink on scans.
- Mobile-friendly UI: Simple uploader, live preview, and a clean progress bar with pass-by-pass status.
Key features
- Quality & DPI sliders: Tune image compression and render resolution.
- Target size goal: Choose ~85%, ~70%, ~50%, ~30% of original or “Smallest”. The tool escalates until the target is hit or best size is found.
- Strategies: Auto (detects image-heavy pages), Raster (force for scans), or Pass-through (metadata only).
- Formats: JPEG (smaller) or PNG (sharper, larger).
- Grayscale mode: Remove color to save more.
- Page ranges: Compress specific pages (e.g.,
1-3,7,end
). - Remove metadata: Strip hidden info to reduce bytes.
- “Never output larger”: When enabled, the tool returns the original file if compression can’t beat it.
- Keeps original filename: Downloads use your input name by default.
How it works (under the hood)
- Each page is inspected. Image-heavy pages are rasterized to a canvas at your chosen DPI; text/vector pages can pass through unchanged.
- Rasterized pages are encoded to JPEG via MozJPEG (or Canvas as a fallback) using your quality/subsampling settings.
- The tool rebuilds a new PDF with optimized images and preserves page size and layout.
- An escalation ladder tries progressively stronger settings until the target is met or the smallest result is found.
Tips for best results
- For scans, choose Auto or Raster strategy with JPEG format and lower DPI (90–110) to maximize shrink.
- Enable Grayscale for black-and-white documents (invoices, receipts) to cut size further.
- Keep Never output larger on if you want to guarantee a non-increasing output size.
- Use Pass-through only when you want to keep text/vector pages untouched and just strip metadata.
Browser compatibility
Works on modern Chromium, Firefox, and Safari. WebAssembly must be available for MozJPEG; if it isn’t, the tool falls back to Canvas-based JPEG encoding.
Privacy & security
All processing happens locally in your browser tab. Files never leave your device.
Troubleshooting
- Output is larger: Lower quality, reduce DPI, switch to JPEG, enable Grayscale, or select a stricter goal.
- Blurry text: Use Pass-through or Auto (so vector text isn’t rasterized), or increase DPI slightly.
- Huge pages crash: The tool caps render size to keep memory safe. Lower DPI or compress in parts (page ranges).