Need to extract text from images or screenshots but don't want to upload sensitive content to cloud services.
Tesseract.js runs OCR entirely in-browser — your data never leaves your device, with zero network transmission required.
01 What is OCR and how does it work?
OCR (Optical Character Recognition) is a technology that converts printed or handwritten text in images into editable digital text. It's widely used for document digitization, data entry, and information extraction.
Traditional OCR tools typically rely on cloud servers for processing, which means your images must be uploaded to a third party. Tesseract.js, however, is an open-source OCR engine built on WebAssembly that runs entirely in-browser with zero server interaction.
The recognition pipeline involves image preprocessing, text region detection, character segmentation, and pattern matching — ultimately outputting clean, selectable plain text.
Tesseract.js downloads language model files (~a few MB) on first load, which are then cached by the browser for faster subsequent use.
02 Uploading images for recognition
Usage is straightforward: click the upload area or drag-and-drop an image directly onto the page to start recognition. Common formats like PNG, JPG, JPEG, BMP, and WebP are all supported.
For best results, upload images with clear resolution and high text contrast. Blurry, skewed, or low-resolution images may reduce recognition accuracy.
- PNG — Recommended, lossless compression preserves detail
- JPG/JPEG — Common format for photos and screenshots
- BMP — Uncompressed bitmap format
- WebP — Efficient modern format supported by all browsers
03 Selecting the right language for best accuracy
The OCR engine relies on pre-trained language models to recognize characters. Selecting the language that matches the text in your image is the most critical step for maximizing accuracy.
If your document contains multiple languages (e.g., mixed Chinese and English), you can select multiple language models simultaneously. Keep in mind that selecting too many models may increase processing time and slightly reduce single-language precision.
For Chinese content, select the "Simplified Chinese" or "Traditional Chinese" model. English content works excellently with the default English model.
If unsure about the document's language, try the English model first — it can often partially recognize other Latin-script languages as well.
04 Getting and copying results
Once recognition is complete, the extracted text appears in the results area. You can select text directly for copying, or use the one-click copy button to copy all text to your clipboard.
Results are in plain text format, ready to paste into document editors, emails, note-taking apps, or anywhere else you need. If you spot occasional misrecognized characters, you can manually correct them before use.
Since all processing happens locally, your images are never stored or logged by any server — even after you close the browser.
FAQ
How accurate is browser-based OCR?
For clear printed text, Tesseract.js typically achieves over 90% accuracy. Results depend on image quality, text size, font type, and language model selection. High-resolution, high-contrast images yield the best outcomes.
Is my image data uploaded during the recognition process?
Absolutely not. All OCR processing happens locally in your browser — no image or text data is ever sent to any external server. This is one of the core advantages of our tool.
Can OCR recognize handwritten text?
Tesseract.js is primarily optimized for printed text. It may partially recognize neat handwriting, but accuracy will be noticeably lower than for printed text. For complex handwriting, a specialized handwriting recognition service is recommended.
What if recognition is slow for large images or multi-page documents?
Processing speed depends on your device's performance and image size. Try cropping images to keep only the text region, or reduce resolution to an appropriate level (300 DPI is usually sufficient). Processing multi-page documents in batches is also an effective optimization.
Which browsers support this OCR tool?
All modern browsers that support WebAssembly are compatible, including the latest versions of Chrome, Firefox, Edge, and Safari. Using the latest browser version is recommended for the best performance and compatibility.
Try the Tool Now
Tesseract.js runs OCR entirely in-browser — your data never leaves your device, with zero network transmission required.