Do you mock your APIs?

Hey everyone,

I'm starting to work on a new project that is going to use Next.js/React for the frontend. I could either build the backend and frontend simultaneously but that would require a fair bit of context switching since my backend is in Rails, or I could build the frontend first and use a mock API as a placeholder until I've built my backend.

How do you all approach this for your projects? If anyone does mock their APIs, any suggestions for a specific library or service to use?

Thanks!