4xx series HTTP status codes help us deal with the API consumer error that is inevitable across API consumption. These status code let applications and integrations know when they have made a mistake requesting resources and capabilities from APIs made available in an automated way.
Utilizing standardized 4xx accurately across all API responses helps API consumers understand when they’ve made a mistake versus when the platform has errored. 4xx series HTTP status codes use the same mechanism as the rest of the web does for communicating user input and configuration error, and APIs are just building on what has already proven to work for the web.