Kirki is the popular WordPress Customizer Framework. Based on this framework, there is also a plugin and it is now 600K+ active installs. Means, more than 600K websites are actively using this plugin. There is no exact measurement of how many users are using a theme based on this framework, however.
According to the owner of Kirki David Vongries, Kirki is looking for a new home. He purchased this plugin from developer of Ari Stathopoulos in April 2020. You can see the tweet from Ari regarding why he sell Kirki before.
Premium version of Kirki is available now. You will get many more customizable feature in the premium version. So, buy purchasing Kirki, you can maintain it and make a good business too.
If you are interested to take over and want to purchase it, you can contact him directly via Twitter or WordPress Slack.
The first release of this plugin was in 2014, 8 years ago. The plugin was developed just to get his job faster.
For WordPress theme developers, you can use this framework to make advanced and powerful customizer using it. This framework is developed based on WordPress theme standards.
There are so many popular WordPress themes are using this framework to provide the best experience for the users.
It has included more than 30 custom controls ranging from slider to Google font integration. Besides that, it has checkbox control, color pallette control, toggle control and many more.
Kirki is released under MIT license and open source and you can use it on both free or commercial projects.
I used this framework for so many projects and I personally recommend to all the theme developers to use this because it’s easy to integrate and customize. Moreover, your users will feel the best customizer experience.
Don’t hesitate to contact me if you have any questions regarding this post.