What is this tool?
Optimize and reduce PDF document file sizes locally inside your browser memory using Ghostscript compiled to WebAssembly (WASM).
When to use it?
Reduce PDF file sizes to meet strict upload limits on government portals, email attachment caps (e.g. 25 MB), job application systems, or mobile document viewers.
How does it work?
Spawns a Web Worker running Ghostscript compiled to WebAssembly. The input PDF is loaded into a virtual memory filesystem (MEMFS), where Ghostscript applies standard PostScript/PDF optimization filters (downsampling images to 150 DPI and removing redundant font descriptors) before outputting the optimized file.
Technical Specifications & Standards
Uses standard Ghostscript PDF write device parameters (/ebook at 150 DPI for balanced quality, /screen at 72 DPI for maximum reduction).
Operating Limits & Considerations
- PDFs that consist primarily of plain vector text without images may experience minimal compression because vector instructions are already compact.
- Very large documents (exceeding 50 MB) require sufficient browser memory for the WebAssembly runtime.
Example Conversions
Upload: scanned_record.pdf (8.5 MB), Preset: Balanced (150 DPI)
Download: scanned_record_compressed.pdf (2.1 MB - 75% reduction)
Frequently Asked Questions
PDFs that contain only vector text, clean fonts, or images that are already heavily compressed will see little reduction. The highest reduction occurs on high-resolution scanned documents with uncompressed raster images.
We recommend the Balanced preset (150 DPI) for general documents and emails. Choose High Compression (72 DPI) only for screen-only viewing where file size is critical.