# How to Use pdf‑inspector WebAssembly: A Complete Guide to Browser‑Native PDF Processing > Learn how to use pdf-inspector WebAssembly for client-side PDF processing directly in your browser. Analyze PDFs without server uploads with this complete guide. - Repository: [Firecrawl/pdf-inspector](https://github.com/firecrawl/pdf-inspector) - Tags: how-to-guide - Published: 2026-08-31 --- **pdf‑inspector WebAssembly lets you run the full Rust PDF analysis engine directly in the browser, processing PDFs client‑side without sending bytes to any server.** The `firecrawl/pdf-inspector` repository ships a lightweight WASM bundle built with **wasm‑bindgen**, exposing a synchronous JavaScript API for PDF classification, Markdown extraction, and text processing. This guide walks through the architecture, installation, and practical usage patterns based on the actual source code implementation. --- ## WebAssembly Module Architecture The WASM binding layer lives in [[`wasm/src/lib.rs`](https://github.com/firecrawl/pdf-inspector/blob/main/wasm/src/lib.rs)](https://github.com/firecrawl/pdf-inspector/blob/main/wasm/src/lib.rs) and follows a clean separation between JavaScript interop and core Rust logic. ### TypeScript Type Generation The module embeds custom TypeScript definitions via `#[wasm_bindgen(typescript_custom_section)]` ([source line 8‑66](https://github.com/firecrawl/pdf-inspector/blob/main/wasm/src/lib.rs#L8-L66)). This provides IDE autocomplete for `processPdf` options including `pages`, `password`, `profile`, and `includePageMarkers`. ### Option Handling Pipeline Two functions bridge JavaScript inputs to Rust internals: - **`deserialize_options`** ([source line 78‑84](https://github.com/firecrawl/pdf-inspector/blob/main/wasm/src/lib.rs#L78-L84)) — Converts `JsValue` into `WasmProcessOptions`, gracefully handling `undefined`/`null`. - **`build_options`** ([source line 86‑118](https://github.com/firecrawl/pdf-inspector/blob/main/wasm/src/lib.rs#L86-L118)) — Maps `WasmProcessOptions` to core `PdfOptions`, validating 1‑indexed page numbers and converting `profile` strings (`"fidelity"` or `"compact"`) to the `MarkdownProfile` enum. ### Processing Entry Point The `process_pdf` function ([source line 29‑40](https://github.com/firecrawl/pdf-inspector/blob/main/wasm/src/lib.rs#L29-L40)) orchestrates execution: 1. Calls `initialize()` to install `console_error_panic_hook` for readable JavaScript stack traces ([source line 25‑27](https://github.com/firecrawl/pdf-inspector/blob/main/wasm/src/lib.rs#L25-L27)). 2. Builds `PdfOptions` with `ProcessMode::Full`. 3. Measures timing via `js_sys::Date::now()`. 4. Delegates to `pdf_inspector::process_pdf_mem_with_options` ([source line 35‑36](https://github.com/firecrawl/pdf-inspector/blob/main/wasm/src/lib.rs#L35-L36)). 5. Wraps results in `WasmPdfProcessResult` and serializes to JavaScript. All exported functions—`detectPdf`, `classifyPdf`, `extractText`, and `version`—follow this same pattern, varying only in `ProcessMode` and return shape. --- ## WebAssembly API Reference | Export | Description | Process Mode | |--------|-------------|--------------| | `processPdf(data, options?)` | Full classification + structured Markdown extraction | `Full` | | `detectPdf(data, options?)` | Classification only, no Markdown | `Detect` | | `classifyPdf(data)` | Lightweight classification matching Node.js API shape | `Classify` | | `extractText(data)` | Plain text without Markdown formatting | `Extract` | | `version()` | Returns WASM package version string | — | After the initial asynchronous `init()` call to load the binary, **all functions are synchronous**—enabling straightforward integration in UI components or Web Workers. --- ## Installing and Initializing pdf‑inspector WebAssembly Add the package via npm: ```bash npm install @firecrawl/pdf-inspector-wasm ``` The entry point exports an `init` function that must be called once before using any processing functions: ```typescript import init, { processPdf, detectPdf, classifyPdf, extractText, version } from "@firecrawl/pdf-inspector-wasm"; async function initialize() { // Required: loads the .wasm binary into memory await init(); console.log("WASM ready, version:", version()); } initialize(); ``` --- ## Processing PDFs in the Browser: Code Examples ### Full Processing with Markdown Extraction Load a PDF via fetch and extract structured Markdown: ```typescript import init, { processPdf } from "@firecrawl/pdf-inspector-wasm"; async function extractMarkdown(pdfUrl: string) { await init(); const response = await fetch(pdfUrl); const pdfBytes = new Uint8Array(await response.arrayBuffer()); const result = processPdf(pdfBytes); console.log("PDF type:", result.pdfType); // "TextBased" | "Scanned" | "Mixed" | "ImageBased" console.log("Pages needing OCR:", result.pagesNeedingOcr); console.log("Markdown:", result.markdown); // Structured markdown string console.log("Processing time (ms):", result.durationMs); return result; } ``` ### Lightweight Detection Only For scenarios where you only need classification without extraction: ```typescript import init, { detectPdf } from "@firecrawl/pdf-inspector-wasm"; async function quickDetect(pdfBytes: Uint8Array) { await init(); const result = detectPdf(pdfBytes); // result contains pdfType, pageCount, confidence scores console.log("Detected:", result.pdfType); return result; } ``` ### Selective Page Processing with Options Process specific pages and choose output formatting: ```typescript import init, { processPdf } from "@firecrawl/pdf-inspector-wasm"; async function selectiveExtract(pdfBytes: Uint8Array) { await init(); const options = { pages: [1, 3, 5, 7, 9], // 1-indexed page numbers profile: "compact", // "fidelity" or "compact" includePageMarkers: true, // Insert `` markers password: undefined, // Optional: decryption password }; const result = processPdf(pdfBytes, options); console.log(result.markdown); } ``` ### Plain Text Extraction Skip Markdown formatting entirely: ```typescript import init, { extractText } from "@firecrawl/pdf-inspector-wasm"; async function getPlainText(pdfBytes: Uint8Array) { await init(); const text = extractText(pdfBytes); // Returns raw concatenated text without structural formatting return text; } ``` ### Node.js‑Compatible Classification Match the API shape used by server‑side bindings: ```typescript import init, { classifyPdf } from "@firecrawl/pdf-inspector-wasm"; async function classify(pdfBytes: Uint8Array) { await init(); const classification = classifyPdf(pdfBytes); // Minimal shape: { pdfType, confidence, isScanned, pageCount } return classification; } ``` --- ## Client‑Side Security Model The parser runs **entirely within the browser**—no PDF bytes are transmitted to external servers ([source line 45‑48](https://github.com/firecrawl/pdf-inspector/blob/main/wasm/README.md#L45-L48) of the WASM README). This architecture suits: - Privacy‑sensitive document processing - Healthcare or financial applications with compliance requirements - Offline‑capable web applications --- ## Key Source Files | File | Purpose | |------|---------| | [[`wasm/README.md`](https://github.com/firecrawl/pdf-inspector/blob/main/wasm/README.md)](https://github.com/firecrawl/pdf-inspector/blob/main/wasm/README.md) | Installation, build instructions, and security notes | | [[`wasm/src/lib.rs`](https://github.com/firecrawl/pdf-inspector/blob/main/wasm/src/lib.rs)](https://github.com/firecrawl/pdf-inspector/blob/main/wasm/src/lib.rs) | WASM binding layer: TypeScript definitions, option serialization, exported functions | | [[`src/lib.rs`](https://github.com/firecrawl/pdf-inspector/blob/main/src/lib.rs)](https://github.com/firecrawl/pdf-inspector/blob/main/src/lib.rs) | Core public API (`process_pdf_mem_with_options`) shared by CLI, Node.js, and WASM | | [[`src/detector.rs`](https://github.com/firecrawl/pdf-inspector/blob/main/src/detector.rs)](https://github.com/firecrawl/pdf-inspector/blob/main/src/detector.rs) | PDF type detection: TextBased, Scanned, Mixed, ImageBased classification | | [[`src/markdown/convert.rs`](https://github.com/firecrawl/pdf-inspector/blob/main/src/markdown/convert.rs)](https://github.com/firecrawl/pdf-inspector/blob/main/src/markdown/convert.rs) | Text‑to‑Markdown conversion with profile selection | The WASM layer is a thin wrapper around this core library—the same Rust code powers the `pdf2md` CLI tool and native Node.js bindings. --- ## Summary - **Initialize once**: Call `init()` asynchronously to load the WASM binary, then use synchronous API calls. - **Choose your mode**: `processPdf` for full extraction, `detectPdf` for classification, `extractText` for plain text. - **Control output**: Use `options.pages` for selective processing and `options.profile` to toggle between `"fidelity"` and `"compact"` Markdown. - **Stay private**: All processing happens client‑side with no network transmission of PDF data. - **Single codebase**: The WASM module delegates to `pdf_inspector::process_pdf_mem_with_options` and related functions from the core Rust library. --- ## Frequently Asked Questions ### How do I load the WASM binary in a bundler like Vite or webpack? The `@firecrawl/pdf-inspector-wasm` package includes the `.wasm` file as a base64‑encoded or separate asset depending on your build tool. Call `init()` without arguments to use the default bundler integration, or pass a custom URL: `init(binaryUrl)`. Check your bundler's WASM handling documentation for optimal chunking. ### Can I use pdf‑inspector WebAssembly in a Web Worker? Yes. Since `init()` is the only async function and all processing calls are synchronous, you can load and initialize the module in a dedicated worker, then process PDFs off the main thread. Pass `Uint8Array` data via `postMessage` or `Transferable` objects. ### What PDF features trigger OCR requirements? According to the detector implementation in [[`src/detector.rs`](https://github.com/firecrawl/pdf-inspector/blob/main/src/detector.rs)](https://github.com/firecrawl/pdf-inspector/blob/main/src/detector.rs), pages are flagged for OCR when they contain no extractable text streams, have image‑only content, or show low text density relative to page area. The `pagesNeedingOcr` array in `processPdf` results identifies these specifically. ### How does the `"compact"` profile differ from `"fidelity"`? As implemented in [[`src/markdown/convert.rs`](https://github.com/firecrawl/pdf-inspector/blob/main/src/markdown/convert.rs)](https://github.com/firecrawl/pdf-inspector/blob/main/src/markdown/convert.rs), `"fidelity"` preserves header hierarchies, lists, and tables with structural Markdown, while `"compact"` collapses formatting to minimize token count for LLM consumption—merging adjacent text and simplifying list markers.