What is OCR?
Optical Character Recognition (OCR) converts images of text into machine-readable text. For PDFs, this means transforming scanned documents from "pictures of text" into actual searchable, selectable text.
How Modern OCR Works
Today's OCR engines use machine learning:
- •Image preprocessing: Deskewing, noise removal, binarization
- •Text detection: Finding regions containing text
- •Character recognition: Neural networks identify each character
- •Language modeling: Context improves accuracy (e.g., "tbe" → "the")
- •Layout analysis: Preserving columns, tables, reading order
OCR Accuracy Factors
Recognition accuracy varies significantly:
| Document Type | Typical Accuracy | Notes |
|---|---|---|
| Clean printed text (300 DPI) | 99%+ | Nearly perfect |
| Newspaper/book scans | 95-98% | Some errors in small text |
| Faded or low-contrast | 80-95% | Preprocessing helps |
| Handwriting | 60-85% | Highly variable |
| Mixed languages | 90-97% | Depends on language pair |
Language Support
OCR engines support different languages with varying accuracy. Latin-alphabet languages work best. Chinese, Japanese, and Korean require specialized models. Our tool supports English, Chinese (Simplified), and mixed documents.
When to Use OCR
Use OCR when you have:
- •Scanned paper documents
- •Photos of documents
- •PDFs where you can't select text
- •Image-based PDFs from older scanners
OCR Output Options
After OCR, you can get: searchable PDF (invisible text layer over images), plain text file, or Word document. The searchable PDF preserves visual appearance while adding text functionality.
Related Tools
FAQ
How do I know if my PDF needs OCR?
Try to select text in your PDF viewer. If you can't select individual words, it's an image-based PDF that needs OCR.
Does OCR work on handwriting?
Modern OCR can recognize some handwriting, but accuracy is much lower than printed text. Results vary widely based on handwriting clarity.
Is OCR processing private?
In browser-based tools like ours, OCR runs locally on your device. In cloud tools, your document is uploaded for server processing.