Two ways to pass data through URLs — and knowing when to use each one. When I first started building APIs with Express, I kept confusing two things: when should the data go in the URL, and when should it go after the URL? Like, what's the difference between these two requests? /users/42 /users?id=42 Enter fullscreen mode Exit fullscreen mode Both pass the number 42 to the server. Both work. But they mean fundamentally different things, and using the wrong one leads to messy, confusing APIs that other developers (and your future self) will hate. The answer came down to a simple mental model I picked up in the ChaiCode Web Dev Cohort 2026: URL parameters identify what you want. Query strings modify how you want it. Once that clicked, I never confused them again. Let me show you.…