What’s the best way to receive SMS online for phone verification?

It really depends on your location. I'm based in Uganda, and I use Africa's Talking, which works well for me. You might find something similar depending on where you’re operating from.

We've built something called Prelude designed just for this purpose. It offers two endpoints with global coverage right off the bat, and no need for country-specific configuration. Plus, it's pay-as-you-go—so you only pay the actual carrier costs without any markup. Their system also does smart routing to help avoid charges for fake users. Super quick to set up too! Check it out at Prelude.so.

What kind of volume are you anticipating? If you're just starting out and expect low traffic, any pay-as-you-go service should work fine. But if you’re aiming for larger scale, make sure to choose a service that guarantees solid uptime.