Verification and validation are two of the most important — and most frequently muddled — ideas in software quality. They sound similar but ask very different questions.
Verification
"Are we building the product right?"
- Checks the product against its specification.
- Done through reviews, inspections, and static checks.
- Happens throughout development, often before code runs.
- Answers: does it meet the documented requirements?
Validation
"Are we building the right product?"
- Checks the product against real user needs.
- Done through actual execution and testing.
- Happens once there is something to run.
- Answers: does it actually solve the user's problem?
Why you need both
A product can pass verification yet fail validation: it perfectly matches a specification that was wrong in the first place. Equally, software can feel useful in demos yet quietly violate its requirements. Only by doing both do you confirm the product is built correctly and is the correct product to build.
Quick memory aid: Verification = specification (documents). Validation = expectation (users).
Conclusion
Verification confirms you followed the plan; validation confirms the plan was right. Treating them as complementary — not interchangeable — is a hallmark of mature quality practice.