Altcha Captcha is a module for Omeka S which adds ALTCHA to the CAPTCHA options in the global settings. ALTCHA is self-hosted: visitors solve a small proof-of-work challenge in their browser, and your site checks the answer itself, without contacting a third-party service.
After installing the module, select "ALTCHA (self-hosted)" under Settings > Security > CAPTCHA. The module requires Omeka S 4.3 or later, and your site must be served over HTTPS, since the widget relies on browser features that only work on secure pages.
Release downloads include the ALTCHA PHP library. If you install from a git clone instead, run this before activating the module, which won't load without it:
composer install
The ALTCHA widget is included, in asset/vendor/altcha/. To update it, change its
version in package.json, then run:
npm install
npm run build
Altcha Captcha is Copyright © 2026-present Corporation for Digital Scholarship, Vienna, Virginia, USA http://digitalscholar.org
The Corporation for Digital Scholarship distributes the Omeka source code under the GNU General Public License, version 3 (GPLv3). The full text of this license is given in the license file.
The Omeka name is a registered trademark of the Corporation for Digital Scholarship.
Third-party copyright in this distribution is noted where applicable. The following are distributed under the MIT License:
- The ALTCHA widget is Copyright © 2023-present Daniel Regeci, BAU Software s.r.o.
(see
asset/vendor/altcha/LICENSE.txt). - The ALTCHA PHP library is Copyright © 2023 Daniel Regeci (see
vendor/altcha-org/altcha/LICENSE.txt).
All rights not expressly granted are reserved.