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ISO Glossary

Verification vs validation

Two requirements that are constantly conflated. Verification asks whether you built it to specification. Validation asks whether it works for its intended use.

Both words appear throughout ISO standards and they mean different things. Evidence of one does not discharge the other.

Verification

Did we build it to the specification? Verification confirms that outputs meet the input requirements — checking a dimension against a drawing, reviewing a design against its inputs, confirming a document says what it was supposed to say.

Validation

Does it work for its intended use? Validation confirms that the resulting product or service meets the requirements for its specified application. It looks past the specification to the purpose.

A part can be perfectly verified — every dimension within tolerance — and fail validation because the specification itself was wrong for the application.

Where each appears

In design and development, clause 8.3.4 requires both. Design reviews with no evidence of validation are a routine finding.

In production, clause 8.5.1 requires validation and periodic revalidation of any process whose output cannot be verified by subsequent monitoring or measurement. These are special processes — welding, heat treatment, plating, adhesive bonding, sterilisation — where you cannot inspect the result without destroying it. The process itself must be validated and the operators qualified.

In software and information systems

The same distinction applies. Verification asks whether the system was built as specified; validation asks whether it does the job the user actually needs. Testing against requirements is verification. User acceptance is validation.

All glossary terms