MCP Server · REST API Live since Aug 2026

📄 PDF Slim API

Server-side PDF compression powered by MuPDF. Compress any PDF to an exact target size (50KB, 1MB, 5MB...) with one call — built for AI agents and developers.

Why PDF Slim API

For AI Agents

Native MCP endpoint — plug into Claude, Hermes, Cursor
Self-describing tools: compress / optimize / inspect
Free 20 calls/day per IP for integration testing
Error messages carry human-readable guidance

For Developers

Simple REST: POST file → get compressed PDF
Target-size compression (not just "less")
100MB file support on paid plans
No signup to try — anonymous tier works immediately

For End Users

No uploads to third parties
Compression quality comparable to desktop tools
93% size reduction on typical documents
Free website: pdfslim.app (browser-based)

Quick Start (REST)

POST/api/v1/compress?target=500000

Upload a PDF as the raw request body. Get the compressed PDF back with metadata headers.

curl -X POST "https://api.pdfslim.app/api/v1/compress?target=500000" \
  --data-binary @input.pdf \
  -o output.pdf

# Response headers:
# X-Pdf-Reduction: 82.3%
# X-Pdf-Reached-Target: true
# X-Pdf-Pages: 12

POST/api/v1/inspect

Get page count, size, and password status before processing.

curl -X POST "https://api.pdfslim.app/api/v1/inspect" \
  --data-binary @input.pdf
# → {"pages":12,"size_bytes":5821000,"size_mb":5.55,"needs_password":false}

POST/api/v1/optimize

Lossless optimization (garbage collection + stream re-compression).

Quick Start (MCP — for AI agents)

Point any MCP client at:

https://api.pdfslim.app/mcp

Tools exposed:

Tool	Purpose
`compress_pdf`	Compress to target size (base64 in, base64 + stats out)
`optimize_pdf`	Lossless optimization
`inspect_pdf`	Page count / size / password check

💡 AI agents: the tool descriptions include quota and upgrade guidance, so your agent can tell users exactly how to handle large files or quota limits.

Auth & Limits

Plan	Calls	Max file	Price
Anonymous	20 / day / IP	10 MB	Free
Starter Key	5,000 / month	100 MB	$9.9 / month

Send your key: Authorization: Bearer YOUR_KEY

curl -X POST "https://api.pdfslim.app/api/v1/compress?target=1000000" \
  -H "Authorization: Bearer YOUR_KEY" \
  --data-binary @input.pdf -o output.pdf

Starter

$9.9/month

5,000 calls / month
100 MB max file size
All 3 endpoints
Monthly auto-renew

Get a key

Free Website

Browser-based, files never leave device
All tools: compress / merge / split / more
No account needed

Use the website

Why MuPDF

PDF Slim API runs MuPDF (the C engine behind Ghostscript) compiled to WebAssembly on Cloudflare Workers. It renders each page and re-encodes at tuned quality/resolution — the same strategy desktop tools use, with pixel-level control. Typical results: 82–93% size reduction on scanned documents.