What is OCR?
OCR (Optical Character Recognition) is a technology that transforms an image containing text into real, editable and copyable text.
Concretely, if you scan a printed page, you get an image. That image is unusable in a word processor: you cannot modify it, search it or reformat it. OCR analyzes the image and extracts the text.
Two main OCR families
In 2026, OCR comes in two main approaches:
1. Local OCR (in the browser or on the device)
Processing is done directly on your device, via a library like Tesseract.js (a JavaScript version of the Tesseract engine, originally developed by HP then maintained by Google).
Characteristics: - No file sent to a server - Works offline once the model is downloaded - Free and unlimited - Performance depends on scan quality
2. Cloud OCR (via AI)
Processing is done on remote servers, often via generative AI APIs like OpenAI's GPT-4o Vision or Google Cloud Vision.
Characteristics: - Excellent performance on difficult text (handwriting, poor-quality photos) - Requires an internet connection - File sent to the server then to the API - Pay-per-use cost (per page or per request)
Detailed comparison
Performance on printed text
On good-quality printed text (digital PDF, 300 DPI scan), Tesseract and GPT-4o Vision achieve comparable results. Accuracy often exceeds 98%.
Verdict: tie.
Performance on handwriting
This is where modern AIs shine. GPT-4o Vision was trained on millions of handwritten documents and recognizes very varied handwriting. Tesseract, on the other hand, often fails on handwriting.
Verdict: clear advantage to cloud OCR.
Performance on poor-quality photos
A photo taken with a phone, with mediocre lighting, an angle or blur, is difficult for classic OCR. Modern AIs are more robust.
Verdict: advantage to cloud OCR.
Privacy
With local OCR, nothing leaves your device. With cloud OCR, the file is sent to a server, then transits to the provider's API. Even with strict privacy policies, you lose control.
Verdict: clear advantage to local OCR.
Cost
Local OCR is free. Cloud OCR typically costs between 0.01 and 0.05 euros per page depending on the provider.
Verdict: advantage to local OCR.
Speed
On a 10-page document, local OCR takes 30 to 60 seconds. Cloud OCR takes 10 to 20 seconds but requires file upload.
Verdict: slight advantage to cloud OCR.
Offline operation
Local OCR works offline after the first model download. Cloud OCR requires a connection.
Verdict: advantage to local OCR.
How to choose?
The rule is simple:
Choose local OCR if:
- Your documents are printed and of good quality
- Your documents are sensitive (personal data, contracts, invoices)
- You often work offline
- You want to avoid any cost
Choose cloud OCR if:
- Your documents are handwritten
- Your documents are poor-quality photos
- Your documents are non-sensitive
- Speed matters more than privacy
The IWELAH approach
At IWELAH, we offer both approaches:
- **OCR PDF (Tesseract)**: 100% local. No file sent. Ideal for sensitive documents and quality scans.
- **Manuscript OCR (AI)**: AI cloud processing. Sends your pages to OpenAI Vision for maximum precision on handwriting.
Each tool clearly indicates its processing mode. You choose with full knowledge.
Best practices to maximize OCR quality
For local OCR
- **Scan at 300 DPI minimum**: this is the quality threshold for Tesseract.
- **Straighten pages** before scanning: Tesseract handles large angles poorly.
- **Avoid shadows**: uniform lighting.
- **Use PNG or TIFF** rather than JPG (less compression).
For cloud OCR
- **Frame correctly**: avoid cut edges.
- **Reduce noise**: avoid busy backgrounds.
- **Process in short batches**: AIs perform better on groups of 5-10 pages.
Conclusion
Local OCR and cloud OCR are not competitors, they complement each other. A good workflow uses local OCR for common documents and cloud OCR for difficult cases or handwriting.
The key is knowing what happens with your files. IWELAH tools always clearly display the processing mode. You will never be surprised by a hidden upload.
Try both tools to see which fits your needs.