Conditional Request

ELI5 — The Vibe Check

A conditional request asks the server 'has this changed since last time I checked?' If not, the server saves bandwidth by just saying 'nope.' It's like calling a restaurant to ask 'did the menu change?' instead of driving there to read it again.

Real Talk

Conditional requests use HTTP headers (If-None-Match, If-Modified-Since, If-Match) to make requests contingent on the resource's current state. The server evaluates the condition and either returns the full response (200) or a lightweight confirmation (304 Not Modified, 412 Precondition Failed). Used for caching validation and safe concurrent updates.

When You'll Hear This

"Conditional requests reduced our API bandwidth by 60% for mobile clients." / "Use If-Match with ETags to prevent lost updates on concurrent edits."