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Calamari OCR

Free#27 of 29 in OCR API Software

Calamari OCR: A focused OCR engine for trainable text-line recognition, not a hosted document API. Ranked #27 of 29 in OCR API Software by our editors (5.6/10); pricing: Open source; best for trainable historical-document OCR.

5.6/10Editor score

Visit Calamari OCR

Calamari OCR5.6 Visit Calamari OCR

At a glance

Editor score
5.6 / 10
Pricing
Open source
Best for
Trainable historical-document OCR
Paid from
Free
Structure extraction
Yes
Facts checked
20 Sep 2026

Where it wins
- Free, open-source engine with self-hosted deployment
- Custom model training plus pretrained model repositories
- Confidence voting, character positions, and prediction probabilities
Where it doesn't
- Processes segmented text lines rather than complete document pages
- Page segmentation and preprocessing require other software
- No hosted REST OCR API; integration centers on Python and CLI

Our verdict on Calamari OCR

Calamari OCR is an open-source Python engine for recognizing text lines in images. It is aimed at developers, researchers, and teams working with historical documents or other OCR projects that need trainable models. The product provides both a Python prediction API and command-line tools for prediction and evaluation, making it suitable for integration into Python scripts and self-hosted workflows. Its focus is segmented text-line recognition rather than complete-page OCR.

Its strongest capability is model customization. Calamari supports custom OCR model training, pretrained model repositories, and GPU-enabled training and prediction configuration. Confidence voting across multiple models can support prediction workflows, while character positions and prediction probabilities expose useful recognition metadata. Dataset support includes PageXML, ABBYY, HDF5, and plain-file formats. These features make it a fit for specialized OCR work where the model and prediction output need more control than a basic recognition endpoint provides.

Calamari requires a technical workflow around the OCR engine. Page segmentation and preprocessing require other software, and the product is an installable self-hosted engine rather than a hosted REST OCR API. Choose it if you need open-source line OCR, Python or command-line integration, and the ability to train or evaluate custom models. Choose another tool if you need a ready-made service that accepts complete document pages, handles preprocessing and segmentation, or exposes a hosted REST interface.

Your product? Our editors can test Calamari OCR in depth and publish a review, labelled as paid · from $149/mo →

Calamari OCR pricing

Plans Open sourceFree Free to use — no paid tier required for the core job.

See plans on github.com

Calamari OCR fact sheet

Free plan	Not verified
Paid from	Free
Structure extraction	Yes
Handwriting OCR	Yes
Table extraction	Not verified
Asynchronous processing	Not verified
Maximum file size	Not verified
SDK languages	Python
Deployment	Self-hosted
Support	Community, Docs
Built for	Solo, Small business (editorial estimate)
Pricing	Open source
Website	github.com
Facts checked	20 Sep 2026

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Featured on iTechGuides

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Reviewed by iTechGuides Editors · Editorial team · Updated Oct 2026

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Last updated 7 Oct 2026 · How we research and update