It’s not free. A subscription is required to use it.
Response from developer
Thank you for your review. The subscription is mentioned in the description of the app in the App Store, but you may have missed it. You can always try out the app for free to see if you like it and how it compares.
This is useless
Response from developer
I'm sorry you feel that way and that Filtre wasn't for you!
A great extension
Response from developer
Thank you so much for your kind review! I'm glad you like Filtre!

