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Strategic insights
Usability Severity Rating - Improved

Written by on February 2, 2005

When testing a product, it is important to rate the severity of the issues found. This will help focus your efforts, and keep an overall summary of the current status of your product. This is nothing new, severity ratings has been around for a long time and has proven useful too.

But, testers and developers are not rating usability problem as they should. Current scales encourage people to see usability issues as secondary. Usability is also rated differently than other types of bugs, causing developers to threat them differently too.

We need a fix, so I am introducing a new, improved "Usability Severity Rating Scale". It is modified version of the scales used by e.g. Bugzilla since there is no difference between a program bug and a usability bug. Many companies fail to understand this, but for a person using your product, it is the same.

Example: if - say - printing a document does not work because of a bug in the software, or because the interface is beyond your understanding. The result is the same - You cannot print. So a usability issue is just as serious as any other types of issues.


Usability Severity Rating Scale

  • 0: Not an issue
    but might be considered a future enhancement
  • 1: Minor
    Issues like cosmetic errors, spelling problems, non-critical workflow issues
  • 2: Serious
    Normal status for an issue
  • 3: Major
    Loss of functionality, problematic impact on a person's workflow
  • 4: Critical
    System crashes, workflows breaks down, complete loss of focus for a specific task. Loss of information
  • 5: Fatal
    Blocker, the issue prevents further use.

Note: Never release a product before all issues between 2 (serious) and 5 (fatal) are fixed. A company that fails to do this is clearly saying that they do not care about people.


No "normal" rate

In Bugzilla and in Jakob Nielsen's severity scale you have a balance between minor and major issues. This indicates that you can have just many non-critical issues as you can have critical ones.

This is problematic. Having issues labeled with normal, minor, trivial, enhancement, cosmetic etc. lack a sense of urgency. It is hard to really feel that a normal issue is important. So the scale is not balanced, and there are no normal issues. The "normal" status is labeled "Serious", which tend make it more important.

Note: How can you have a normal bug anyhow - for something to be normal is has to happen repeatedly. A normal bug would be something you have had in several version of your product.

Two non-critical ratings is included. "Not an issue" and "Minor", for issues that really does not matter to person using your product. Fixing these would not have a profound effect, but will merely add a sense of professionalism.


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Thomas Baekdal

Thomas Baekdal

Founder of Baekdal, author, writer, strategic consultant, and new media advocate.

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