Device & Permission APIs

The gated set includes camera and microphone (getUserMedia), geolocation, notifications, clipboard read, persistent storage, screen capture, Bluetooth, USB, MIDI, and idle detection. They share a model: HTTPS required, a user gesture required for most, and a browser-controlled prompt you cannot style, move, or retry.

That last point drives everything. A user who clicks "Block" is not asked again by that browser, and re-enabling means digging through site settings — which almost nobody does. So a prompt fired on page load, before any context, converts a curious visitor into a permanently blocked one. The correct pattern is to ask in response to an action that obviously needs it, ideally after a short in-app explanation of why: press "Start call", then the prompt appears and its purpose is self-evident. Some browsers now suppress prompts entirely when they arrive without a gesture.

The Permissions API lets you query current state — granted, denied, or prompt — without triggering a request, so you can render honest UI: a disabled button with an explanation for denied, rather than a control that silently does nothing.

Individual notes worth having. Clipboard write is generally allowed from a user gesture; clipboard read is gated and much more restricted. Geolocation has a low-accuracy mode that is cheaper and often sufficient. Notifications are the most abused prompt on the web and the reason browsers added blanket suppression settings. navigator.mediaDevices.enumerateDevices() hides labels until permission is granted, which is a fingerprinting defence.

Every one of these must be feature-detected — support varies widely, especially between Chromium and Safari — and every one needs a designed fallback, because a denial is a normal state, not an error.

Any product with video, location, or notifications hits this, and the difference between a well-designed permission flow and a badly designed one shows directly in grant rates — a product metric, not a technical one.

It also demonstrates user-facing judgement in interviews: explaining why you ask late rather than early is a product answer as much as a technical one.

• Gated APIs require HTTPS, usually a user gesture, and a prompt you cannot style or reliably re-trigger.
• A denial is effectively permanent, so asking without context converts curious users into blocked ones.
• Ask in response to an action that makes the reason obvious, after explaining it in your own UI.
• The Permissions API reports state without prompting, which lets you render honest disabled states.
• Clipboard read is far more restricted than clipboard write; device labels are hidden until permission is granted.
• Feature-detect everything and design the denied path as a normal state.