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Generate PDF files with JavaScript and WASM (WebAssembly)

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Generates PDF files directly in the browser with JavaScript and WASM (WebAssembly).

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Idea here is to push all the work involved in creating a PDF to the browser side, instead of using precious server resources.


Example that generates a sample PDF document from JSON file. Title in PDF is changed dynamically (in JavaScript) to show current date. Note: this example routes directly to the PDF data blob, so 2 backsteps are needed to return to this page.

Another example that generates 400 paragraphs of Lorem Ipsum and shows a download link when document has been generated (which is instantly 🙂). Also shows page numbers.

This example creates a task calendar.


  • PDF contents are described as a JavaScript object and that gets passed to WASM-module, which generates the output
  • Customizable output handler (e.g. load blob URL to a link or directly to window)
  • Currently supported elements include:
    • Paragraphs/text elements with basic fonts (Helvetica, Times, Courier)
    • Images loaded from URL (converted automatically to bytes)
    • Tables with rows and cells
    • Spacers (they just eat space)
    • Paths with points, strokes, fills and alignment
    • Basic styling (all styling parameters are optional)
    • Custom template size (defaults to A4 portrait with 50 px margins)
    • Page numbers and stationary text can be included in template
    • Inline links and bold text (a and b tags) inside paragraph text
  • The generator crate can also be used standalone in a non-browser environment

Example input (JSON)

    "title": "Example Document",
    "contents": [{
            "obj_type": "Paragraph",
            "params": {
                "text": "Hello World!",
                "font_size": 18,
                "leading": 24,
                "align": "center",
                "font_name": "Helvetica-Bold"

How to generate an example PDF

Option 1 (with Rust)

  • First install the Rust compiler
  • Clone this repo:
    git clone
  • Change to directory:
    cd wasm-pdf
  • Install JavaScript libraries:
    npm install
  • Launch the local development server:
    npm run serve
  • Open your browser and visit the url provided by the server, usually

Option 2 (with JavaScript only / npm package)

Special Thanks


This project is licensed under either of

  • Apache License, Version 2.0, (LICENSE-APACHE or
  • MIT license (LICENSE-MIT or

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