MantisPDF is a free, open-source PDF toolkit that runs entirely in your browser. Split, merge, compress, rotate, encrypt, and watermark PDFs using WebAssembly — no uploads, no servers, no tracking.
Your files never leave your browser. All PDF processing runs locally via Rust-compiled WebAssembly.
Most online PDF tools (ilovepdf, smallpdf, etc.) upload your files to their servers. MantisPDF is different:
- No uploads. Your PDFs stay on your machine — always.
- No server, no tracking. There's nothing to breach and nothing to log.
- Rust performance in the browser. PDF operations run in a Web Worker via
wasm-pack-compiled Rust, so the UI stays responsive even on large files. - Open source. MIT — audit it, fork it, self-host it.
- Split PDF — Select exactly where to split and download the parts as a ZIP
- Merge PDF — Combine multiple PDFs into one, with drag-and-drop reordering
- Edit PDF — Delete or reorder pages, download result as
_edited.pdf - Compress PDF — Reduce PDF file size entirely client-side
- Rotate PDF — Rotate individual pages (90°, 180°, or 270°)
- PDF to Images — Export each page as a PNG or JPEG image
- Watermark PDF — Stamp custom text on every page (size, opacity, angle, color)
- Encrypt PDF — Password-protect a PDF so only authorized readers can open it
| Layer | Technology |
|---|---|
| Frontend | React 19, TypeScript (strict), Tailwind CSS |
| Bundler | Vite 6 with WASM + top-level-await plugins |
| PDF engine | Rust + lopdf, compiled to WASM via wasm-pack |
| Preview | react-pdf for page thumbnails |
| Packaging | JSZip for multi-file downloads |
- Node.js >= 18
- Rust toolchain (
rustup) - wasm-pack — install with
cargo install wasm-pack
# Clone the repo
git clone https://github.com/BryanBradfo/mantispdf.git
cd mantispdf
# Build the WASM module (required before first run)
npm run build:wasm
# Install JS dependencies
npm install
# Start dev server
npm run devThe app opens at http://localhost:5173.
mantispdf/
├── crates/mantis-wasm/ # Rust crate — PDF ops compiled to WASM via wasm-pack
├── src/
│ ├── pages/ # Route-level page components (one per tool)
│ ├── components/ # UI components grouped by tool + shared common/
│ ├── hooks/ # usePdfWorker, useSplitState, useMergeState, …
│ ├── workers/ # pdf.worker.ts — WASM init + PDF processing off main thread
│ └── lib/ # workerProtocol.ts, fileHelpers.ts, downloadZip.ts
├── vite.config.ts # WASM plugin config (worker.plugins + optimizeDeps exclude)
└── package.json
Contributions are welcome! For ideas or bug reports, open a Discussion or Issue.
To contribute code:
# Fork the repo, then:
git clone https://github.com/<your-fork>/mantispdf.git
cd mantispdf
npm run build:wasm # build WASM first
npm install
npm run dev # start dev server at localhost:5173Run Rust tests with:
cd crates/mantis-wasm && cargo testThen open a PR against main. Please keep PRs focused — one feature or fix per PR.
- Upload — Drop a PDF onto the DropZone. The file is validated (type + 100 MB limit) and read into an
ArrayBuffer. - Configure — Choose tool-specific options (split points, passwords, watermark text, …).
- Process — The main thread transfers the PDF bytes to a Web Worker via
postMessage. The worker calls the relevant Rust/WASM function (extract_pages,merge_pdfs,encrypt_pdf, …) off the main thread. - Download — The result is transferred back and saved: single files via a Blob URL, multi-part results via JSZip.
UI Thread Web Worker
──────────── ──────────
DropZone → validate & read
Configure tool options
│
├── postMessage(pdfBytes, options) ──→
│ init WASM (once)
│ call WASM fn (lopdf)
│ ←── postMessage(result)
│
downloadBlob / downloadZip → browser saves file