Reference table
Nielsen's usability severity rating scale (0 to 4)
The standard five-point scale for rating usability problems, from 0 (not a usability problem) through cosmetic, minor and major to 4 (usability catastrophe), with what each rating means for the fix. UX researchers and designers use it in heuristic evaluations and usability test reports. Nielsen recommends averaging ratings from three evaluators rather than trusting one. Koji helps by measuring how often each problem happens across many AI-moderated sessions.
Where this appears
What's in this reference table
| Rating | Meaning | What to do |
|---|---|---|
| 0 | Not a usability problem at all | Drop it and log the disagreement |
| 1 | Cosmetic problem only | Fix only if there is spare time |
| 2 | Minor usability problem | Low priority |
| 3 | Major usability problem | Important to fix, high priority |
| 4 | Usability catastrophe | Must be fixed before release |
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<a href="https://www.koji.so/visuals/nielsen-usability-severity-rating-scale-0-4"><img src="https://www.koji.so/visuals/nielsen-usability-severity-rating-scale-0-4/nielsen-usability-severity-rating-scale-0-4.png" alt="Table of the Nielsen 0 to 4 usability severity scale, from 0 not a problem and 1 cosmetic to 4 usability catastrophe, with the action for each rating." width="1200" height="673" /></a>
<p>Source: <a href="https://www.koji.so/visuals/nielsen-usability-severity-rating-scale-0-4">Nielsen's usability severity rating scale (0 to 4)</a>, Koji</p>
