A backend can just say ‘no’ if it gets a number in a format it doesn’t like.

If a user enters a number incorrectly on a frontend, a frontend can’t just say no. It might have to try its best to parse the number, or if it can’t, the error has to be presented in a user friendly way. A frontend can’t just throw an exception and say Bad Request.

> If a user enters a number incorrectly on a frontend, a frontend can’t just say no.

Followed by the distant sound of enterprise, banking, and government frontend devs laughing.

I disagree. Have you ever worked in finance? Inconsistent or unexpected number/date formats have to be dealt with. And to add to it, the formats can be binary and not just text that you can look at it and sort of "figure it out". Often times these files are coming from other large institutions and getting them to fix their data takes days if ever. In the mean time there is daily processing that has to get done in order to trade at the next day's opening.

A system can't just reject data it doesn't like.

Or you just send the input to the backend and have the backend tell the frontend to tell the user "backend said no"

> I can build a decent and reliable frontend with a no code solution

Things that can be built that way are not interesting. Of course you can just assemble online stores without writing a single line of code, but that's not exactly programming. We are talking about frontends that have some sort of novelty or at least non-standard flows in them.

The parent made no such distinction. And your comment applies to just as much to backends as frontends. If a backend is "easy" to make reliable then it's probably not very interesting.

Seems like you don't know much about building frontends.

Sounds like you don't know much about building backends.