Which dating app is 100% free?

I'm curious, can you shed some light on the dating app scene? Specifically, I'm wondering if there's any dating app out there that truly offers 100% free services, with no hidden costs or premium features that you have to pay for? It seems like many apps these days offer a basic free version, but then require you to upgrade for full access. Is there truly a dating app that doesn't follow this model, and if so, what are its features and how does it compare to other popular apps in terms of user base and success stories?