Migration towards version 0.4.0

Please read this page for detailed upgrade information towards version 0.4.0 (released September 2021)


Ocapi is the French acronym for Outil de Captcha et d'Annotation du Patrimoine en Image or "Other Captcha to Annotate Patrimonial Images" in English. It was previously named CaptchAN.

It aims to provide web developers with a user validation system whose content comes from digitized cultural heritage corpora and where the user's action on the challenge allows to validate the annotation and analysis of these corpora.

The objective of Ocapi is to ensure that the user filling in the form on a website is a human user, and not a robot trying to validate the form automatically. It serve a secondary objective, that of validating automatically generated data such as OCRized corpora, indexed photographs, etc. The website users who fill in the challenge then validate the data transparently.

The objective of the Ocapi service is to propose a challenge system using historical data. The aim is to enhance the value of digitized cultural heritage content and to involve Internet users in the validation of indexed or OCRized corpora in an automatic or collaborative way.


You can try Ocapi on our production instance, a demo is showcasing our different use cases on ocapi.teklia.com


This project was an original idea of Karl Pineau, tried out during a Hackathon in 2018.

Teklia worked with the Archives Nationales and Karl to bring that idea to life, and allow public websites to use challenges with historical data.

Karl also wrote another blog post, showcasing the project two years after its creation

In 2021, we renamed the project from Captchan, to Ocapi. You may still find references to the old name in this documentation, we are in the process of renaming all our assets to Ocapi.