PDF Compressor

A free, privacy-first PDF compression web app. Upload a PDF, pick a compression level, and download a smaller file — no sign-up, no cloud storage, files are deleted immediately after processing.

Live demo: (add your Vercel URL here after deployment)

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Features

• Drag & drop PDF upload (up to 50 MB)
• Three compression levels: Low / Medium / High
• Before & after file size with savings percentage
• Instant download — no email, no account
• Files processed in-memory and deleted immediately
• Works on any modern browser

Compression results (real-world PDFs)

Level	PDFSETTINGS	DPI	Typical reduction
Low	/printer	300	0–10%
Medium	/ebook	150	50–65%
High	/screen	72	75–90%

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Tech stack

Layer	Technology
Frontend	React 18 + Vite 5
Styling	TailwindCSS 3
File upload	react-dropzone
HTTP client	axios
Serverless API	Vercel Node.js functions
Compression (primary)	Ghostscript (gs -dPDFSETTINGS)
Compression (fallback)	MuPDF WASM (saveToBuffer compress,garbage=4)
Tests	Vitest + Testing Library (21 tests)

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Project structure

├── api/
│   └── compress.js        # Vercel serverless function (POST /api/compress)
├── src/
│   ├── components/
│   │   ├── Compressor.jsx            # Main orchestrator component
│   │   ├── DropZone.jsx              # Drag & drop file input
│   │   ├── CompressionLevelPicker.jsx
│   │   ├── FileSizeDisplay.jsx       # Before/after + savings bar
│   │   └── ProgressBar.jsx
│   ├── hooks/
│   │   └── useCompress.js            # Upload → compress → download lifecycle
│   └── test/                         # 21 Vitest unit tests
├── server.dev.js          # Local API dev server (mirrors Vercel function)
├── vercel.json            # Vercel deployment config
├── ARCHITECTURE.md        # Detailed architecture & code reference
└── package.json

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Getting started

Prerequisites

• Node.js 20+
• Ghostscript (for full compression — optional, falls back to MuPDF)

# macOS
brew install ghostscript

# Ubuntu/Debian
sudo apt-get install ghostscript

Install dependencies

npm install

Run locally

# Start both the Vite frontend (port 5173) and API server (port 3001)
npm run dev:all

# Or start separately:
node server.dev.js   # API on :3001
npm run dev          # Frontend on :5173

Open http://localhost:5173.

Run tests

npm test              # run once
npm run test:watch    # watch mode

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Deployment (Vercel)

npx vercel --prod

Note: Standard Vercel deployments do not include Ghostscript. The API automatically falls back to MuPDF compression. For full Ghostscript performance, deploy using a Docker-based Vercel runtime or a VPS.

No environment variables are required for the MVP.

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Branch strategy

Branch	Purpose
dev	Active development — all feature branches merge here
staging	Pre-production integration testing
main	Production — deployed to Vercel

Workflow:

feature/my-feature  →  dev  →  PR to staging  →  PR to main

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API reference

POST /api/compress

Request: multipart/form-data

Field	Type	Required	Description
file	PDF file	Yes	Max 50 MB
level	low | medium | high	No	Default: medium

Response (success): 200 application/pdf

Header	Description
X-Original-Size	Original file size in bytes
X-Compressed-Size	Compressed file size in bytes
X-Engine	ghostscript or mupdf

Response (error): 400 / 413 / 500 JSON { "error": "..." }

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License

MIT