Freebird is built using open source software. We are grateful to the developers and communities who create and maintain these projects. Below is a list of key open source libraries we use, along with their licence information.
chroma.js
A JavaScript library for colour conversions and colour scales. Used by Freebird’s Smart Fill feature to analyse colour contrast ratios and detect potential accessibility issues.
Copyright: Gregor Aisch
Licence: BSD-3-Clause and Apache-2.0
axe-core
An accessibility testing engine for websites and applications. Used by Freebird’s Smart Fill feature to automatically detect accessibility issues in webpage elements.
Copyright: Deque Systems, Inc.
Licence: MPL-2.0 (Mozilla Public Licence 2.0)
Freebird also uses many other open source libraries, including React, TanStack, Tailwind CSS, Zustand, XState, Effect, and others. Most of these are released under the MIT licence, which permits commercial use.
For a complete list of dependencies and their licences, please contact us for more information.
Freebird’s Smart Fill feature uses the open source libraries listed above (axe-core and chroma.js) to perform local, rule-based design analysis without sending data to external services. All analysis is performed entirely within your browser, ensuring your privacy and data security.
We are committed to respecting the terms of all open source licences and contributing back to the community where possible. If you believe we have inadvertently failed to provide proper attribution for any open source software, please contact us and we will promptly address the issue.
Last updated: January 2026