Software quality is the degree to which a system satisfies the stated and implied needs of its various stakeholders. (based on ISO/IEC 25010 and the SEBoK glossary)

That’s the working definition we use throughout this site. It’s accurate, and it’s also the kind of sentence you forget the moment you close the tab: it doesn’t tell you what to build, measure, or test for.

The single word “quality” is really a placeholder for a whole set of specific, measurable characteristics — performance, security, maintainability, usability, and dozens of others. On their own, none of these is “quality”; together, structured into a handful of related quality dimensions, they’re what stakeholders actually mean when they ask for a “high-quality” system. A system is never good or bad at “quality” in the abstract — it’s fast or slow, secure or exposed, easy or hard to change.

That’s why this site is organized the way it is: browse the quality characteristics directly, see how they group into dimensions, and attach concrete, testable requirements to each one.

If you want the longer version — why textbook definitions alone don’t help, and what to do about it in practice — read Challenges with Quality.