Benjamin M Brown

Quantifiable performance goals and response times in user experience

This is a copy of Scott Allen’s post on some interesting performance guidelines in the Roslyn codebase.

This is how the Roslyn team objectively defines speed :

An interaction class defines how much time is expected to reach a time point, the response time point being the most commonly used. The interaction classes correspond to human perception,so, for example, all interactions in the Fast class are perceived as fast and roughly feel like they have the same performance. By defining these interaction classes, we can describe performance using adjectives that have a precise, consistent meaning.

Name Target (ms) Upper Bound (ms) UX / Feedback
Instant <=50 100 No noticeable delay
Fast 50-100 200 Minimally noticeable delay
Typical 100-300 500 Slower, but still no feedback necessary
Responsive 300-500 1,000 Slower yet, potentially show Wait cursor
Captive >500 10,000 Long, show Progress Dialog w/Cancel
Extended >500 >10,000 Long enough for the user to switch to something

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