The problem with scans: you can't Ctrl+F them
A scanned contract, an old report, a signed agreement that came back by scanner — each page is just a photograph, so nothing is searchable, nothing is selectable, and document systems can't index a word of it. OCR fixes that: the text in the images is recognized and written into the file as an invisible layer, positioned exactly over the printed words. The document looks pixel-for-pixel the same, but Ctrl+F works, text can be copied out, and search tools finally see the content. Elsewhere this is routinely a paid, premium feature; here it runs free on your own machine.
How the recognition works
Each page is rendered at high resolution and read by Tesseract, the open-source OCR engine, compiled to WebAssembly and self-hosted by this site — after the one-time engine download (about 15 MB), even that needs no further network access. Recognition takes a few seconds per page. The recognized words are then placed over the original pages — which are copied untouched, preserving scan quality — at the exact position of the printed text, so selecting a sentence in the output highlights the right place on the page. Seven languages are supported; picking the right one matters a lot for accuracy.
Private by architecture, honest about limits
Scanned documents are the most sensitive files people hold — signed contracts, medical letters, ID copies — and this tool never transmits them: rendering, recognition, and rebuilding all happen in your browser. Two limits stated plainly: OCR accuracy depends on scan quality (a sharp 300 DPI scan reads nearly perfectly, a blurry phone photo doesn't), and the invisible layer uses the PDF standard's built-in fonts, which cover Latin scripts — for Hindi or Arabic documents, recognized words outside that character set are counted and reported rather than silently dropped.