Frontend

Frontend refers to the part of a website or app that users see with their eyes and interact with using their hands.

A restaurant makes this easy to understand. The dining hall, the menu, and how the waiter takes orders are the frontend, while what happens in the kitchen — actually cooking food and managing ingredients — is backend work that customers never see. The color of buttons on screen, how text is laid out, and even checking in advance what values you're allowed to type into an input box are all jobs the frontend handles.

But the checks the frontend performs are only a first filter happening on screen. The actual place where data gets stored and final decisions get made is somewhere else entirely. So if something goes wrong in that on-screen checking code, even requests that are actually completely fine can end up blocked at the screen stage.

In the article, a Google Workspace sign-up error is explained by saying 'this error was validation that only happened on screen (frontend), not on the server.' The server side, which handles the actual data, was working fine — but there was a problem in the code that pre-filters input values on screen, which ended up blocking sign-ups even for legitimate domains. When you see the phrase 'frontend issue,' it means the server is fine and the problem lies in the code or design of the part users actually see.