In October 2014, when the original CatBlock extension was officially discontinued by Michael at AdBlock, and open-sourced under the GPLv3 license by AdBlock Team, Kieran and Tomáš (at that time members of AdBlock Team), decided to keep CatBlock alive independently.
Kieran & Tomáš left the AdBlock team in early 2016 to put more effort into development of CatBlock, including creating versions compatible with both Mozilla Firefox and Microsoft Edge.
