The Three Rules
- Under 200ms: Don't show anything. It feels instant.
- 200ms - 2s: Show a skeleton screen or subtle indicator.
- Over 2s: Show a progress bar or determinate indicator with context.
Skeleton Screens
- Match the actual content layout (not a generic spinner)
- Animate with a shimmer effect (left-to-right pulse)
- Show 3-5 skeleton items max (not 20)
- Transition smoothly to real content (no flash)
Progress Indicators
| Type | When | Example |
|---|---|---|
| Determinate bar | Known duration/steps | File upload (45% complete) |
| Indeterminate bar | Unknown duration, short wait | Page loading |
| Spinner | Unknown duration, small area | Button loading state |
| Skeleton | Page/section loading | Dashboard loading |
Optimistic Updates
Show the result immediately, sync in the background:
- Toggle switches: flip immediately, revert on error
- Like/bookmark: show filled state instantly
- Message sending: show in chat immediately with "sending..." status
- Use only when failure is rare and reversible
Anti-Patterns
- Full-page spinners blocking all interaction
- Loading spinners that appear for 100ms (use a delay of 300ms before showing)
- No loading state at all (user wonders if their action worked)
- Different loading patterns on the same page
- "Loading..." text without context (loading what?)