How to use OCR PDF
- Select a scanned PDF.
- Tick the languages used in the document (up to three).
- Click “Make searchable”. Download the searchable PDF and, optionally, the recognized text as TXT.
How it works
bopdf renders each page at 300 DPI and runs Tesseract, the open-source OCR engine, inside your browser. The output PDF keeps the page image and adds an invisible text layer on top, so it looks the same but becomes searchable and copyable.
The engine and language data are downloaded once from the jsDelivr CDN (2–15 MB depending on language) and cached by your browser. Your document itself is never uploaded.
Accuracy tips
Clean, straight scans at normal resolution work best. Choose only the languages actually present — adding extra languages slows recognition and can lower accuracy. Handwriting is generally not recognized.
🔒 Your files never leave your device
bopdf processes your documents locally with JavaScript (pdf-lib and Mozilla pdf.js) inside your browser tab. Your PDF is never uploaded, stored or seen by us — you can even disconnect from the internet after the page loads and the tool keeps working. When you close the tab, everything is gone.
Frequently asked questions
Is OCR really done on my device?
Yes. Only the OCR program and language files are downloaded; your PDF is processed locally.
Does it support Chinese?
Yes, Simplified (chi_sim) and Traditional (chi_tra) Chinese, plus Japanese and Korean.
How long does it take?
Roughly 3–15 seconds per page depending on your device and language.
Are my files uploaded to a server?
No. Everything happens in your browser on your own device. Files are never sent over the internet, which makes bopdf suitable for confidential documents.
Is there a file size limit?
There is no fixed limit, but very large files (hundreds of MB) depend on your device memory. On phones, files up to about 100 MB usually work well.