Browser Usage (WASM)

LiteParse ships a WebAssembly package that runs entirely in the browser — no server, no cloud calls. It supports PDF parsing and custom OCR engines implemented in JavaScript.

Install

npm install @llamaindex/liteparse-wasm

Quick start

import init, { LiteParse } from "@llamaindex/liteparse-wasm";

// Load the WASM module
await init();

const parser = new LiteParse({
  ocrEnabled: false,
  outputFormat: "json",
});

// data is a Uint8Array (e.g. from <input type="file"> or fetch)
const bytes = new Uint8Array(await file.arrayBuffer());
const result = await parser.parse(bytes);

console.log(result.text);
console.log(result.pages[0]);

What works in the browser

• PDF parsing from Uint8Array input (use file.arrayBuffer() to get bytes from a file picker for example)
• Custom OCR via the ocrEngine callback interface (see below)
• Text, JSON, and markdown output formats
• Document complexity via parser.isComplex(bytes) — see the complexity guide
• The extraction options — annotations, form fields, structure trees, vector graphics, and the rest. See Extraction options

What doesn’t work

• File path input — pass Uint8Array instead
• DOCX/XLSX/PPTX conversion — requires LibreOffice, which isn’t available in the browser
• Built-in Tesseract or HTTP OCR — use the custom ocrEngine interface instead
• Screenshots — not available in the WASM build
• numWorkers — parsing is single-threaded in WASM; the option is not exposed
• imageOutputDir — there is no filesystem to write to. Use extractImages and read the bytes from the result instead

OCR in the browser

The native Tesseract and HTTP OCR backends are not available in WASM. To use OCR, pass a custom ocrEngine object with a recognize method:

const parser = new LiteParse({
  ocrEnabled: true,
  ocrLanguage: "eng",
  ocrEngine: {
    /**
     * @param imageData PNG-encoded image bytes
     * @param width  rendered page width in pixels
     * @param height rendered page height in pixels
     * @param language e.g. "eng"
     * @returns array of { text, bbox: [x1, y1, x2, y2], confidence }
     */
    async recognize(imageData, width, height, language) {
      // e.g. call a Web Worker wrapping tesseract.js, or a remote OCR service
      return [
        { text: "Hello", bbox: [10, 20, 80, 40], confidence: 0.98 },
      ];
    },
  },
});

This lets you plug in any OCR implementation — a Web Worker running tesseract.js, a cloud OCR API, or anything else that returns text with bounding boxes.

Config options

All optional, camelCase:

Option	Type	Default	Description
ocrLanguage	string	"eng"	Language code passed to the OCR engine
ocrEnabled	boolean	false	Run OCR on text-sparse pages. Off by default in WASM — there is no built-in engine, so this does nothing without ocrEngine
ocrEngine	object	—	Custom JS-side OCR engine (see above)
ocrFailureFatal	boolean	true	When false, OCR failures return partial results instead of throwing
ocrHedgeDelaysMs	number[]	[]	Request-hedging schedule for a remote ocrEngine
maxPages	number	1000	Stop after this many pages
targetPages	string	—	e.g. "1-5,10,15-20"
dpi	number	150	Render DPI for OCR
outputFormat	"json" | "text" | "markdown"	"json"	Shape of result.text. Also accepts "md". Throws on any other value
preserveVerySmallText	boolean	false	Keep tiny text that’s normally filtered
skipDiagonalText	boolean	false	Drop text more than 2° off the nearest right angle
cropBox	{ top, right, bottom, left }	—	Fraction to crop from each side of every page
password	string	—	Password for protected PDFs
quiet	boolean	false	Suppress progress logging
imageMode	"off" | "placeholder" | "embed"	"placeholder"	How image references appear in markdown. Also accepts "none" for off
extractLinks	boolean	true	Render [text](url) in markdown
keepHeadersFooters	boolean	false	Keep running header/footer chrome in markdown
emitWordBoxes	boolean	false	Per-word sub-boxes on each text item

The extraction options — extractImages, extractVectorGraphics, extractAnnotations, extractFormFields, extractStructureTree, extractContentBounds, extractXfaPackets, extractTextMetadata, includeComplexity, and renderFormFields — are all available here too, with the same camelCase names and the same false defaults.