Extract editable text from scanned PDF documents and image files with our free OCR PDF tool. Powered by Tesseract.js WebAssembly optical character recognition running 100% inside client browser RAM, our tool converts scanned pages into searchable text with multi-language support.
Upload a scanned PDF document or image-based PDF requiring optical character recognition.
Select document language and OCR engine resolution settings for text layer extraction.
Click Process OCR to embed searchable text layers into your PDF and download.
Scans scanned documents and image-based PDFs using WebAssembly Tesseract.js to extract editable text characters locally.
Supports 10+ document languages and selectable canvas render scales (1x to 3x) for small fonts.
All canvas rendering and optical character recognition execute inside client browser memory. Zero files leave your device.
Optical Character Recognition (OCR) converts pixel arrays from scanned document images into structured Unicode text. In browser environments, PDF.js renders vector and bitmap PDF pages to HTML5 Canvas elements at custom DPI scaling factors (1x, 2x, 3x).
The rendered canvas pixel context is passed directly to Tesseract.js, a WebAssembly (Wasm) compiled port of Google's open-source Tesseract OCR engine. Tesseract binarizes image pixels, detects line baselines, segments glyph contours, and evaluates them using deep LSTM (Long Short-Term Memory) neural network language models.
Extracted character strings are concatenated per page and formatted into clean text streams. Because processing runs inside browser Web Workers, operations complete with zero network data transfer and absolute file privacy.