Veilgen is described as '-Master is a powerful and flexible fake data generator designed for developers, testers, and security researchers. It supports a wide range of data types, including names, addresses, emails, phone numbers, and even structured JSON data' and is an app. There are more than 10 alternatives to Veilgen for Web-based, Self-Hosted, SaaS and Windows. The best Veilgen alternative is AryaWebStudio, which is free. Other great apps like Veilgen are Mock Turtle, JSONGenerator, Random Data and dbForge Data Generator for MySQL.
It's hard to put together a meaningful UI prototype without making real requests to an API. By making real requests, you'll uncover problems with application flow, timing, and API design early, improving the quality of both the user experience and API.
