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Verification checks whether a software work product conforms to specified requirements; validation checks whether the product meets its intended use and user needs. The familiar shorthand is “Are we building the product right?” for verification and “Are we building the right product?” for validation. Those questions are useful reminders, but the reference point—requirements versus intended use—is what makes the distinction practical.
How verification and validation differ
| Dimension | Verification | Validation |
|---|---|---|
| Main question | Does this work product meet the requirements allocated to this activity? | Does the product meet its intended use and user or mission needs? |
| Reference point | Approved requirements, specifications, or inputs to the development activity | Intended use, concept of operations, customer needs, and realistic operating context |
| Typical evidence | Reviews, inspections, analysis, demonstrations, and tests tied to requirements | Evaluation with typical users or realistic or simulated conditions, including suitability and effectiveness |
| When it applies | At different lifecycle stages, including to intermediate products | Throughout the lifecycle; realistic validation testing is performed on an end product or representative system |
| What it reveals | Conformance evidence, defects, or requirement gaps | Whether the solution is suitable and effective for its intended use, including unmet needs or mistaken assumptions |
NASA’s product verification guidance distinguishes tests against an approved requirements set from validation tests against the concept of operations. Verification testing can take place at different product lifecycle stages; validation testing uses realistic or simulated conditions to assess suitability and effectiveness in operations.
What the distinction looks like in practice
Illustrative login-feature example
Imagine a login feature with approved requirements for account lockout, password reset, and session timeout. A verification activity checks whether the implementation conforms to those requirements. A validation activity asks whether intended users can securely sign in and recover access in the environment where they will actually use the software.
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The same test session can contribute evidence to both activities if the criteria and conclusions remain distinct. For example, a session might establish whether a password-reset requirement works as specified and separately assess whether users can complete account recovery in a realistic context. NASA notes that verification and validation testing may sometimes be combined when justified; that does not make their questions interchangeable.
When to perform V&V
Verification is not simply “before coding,” and validation is not simply “after coding.” IEEE describes verification and validation processes across lifecycle activities, while NASA’s software engineering definitions describe validation as evaluating software products throughout the software development lifecycle.
The reference point changes with the activity. A requirement or design can be checked against its inputs; code or an integrated build can be checked against allocated requirements; and a representative system can be evaluated in an operational or simulated setting for intended use. The key is to state what is being evaluated and against which criteria, rather than assigning each activity a fixed place on the calendar.
Testing is one V&V method, not a synonym
Running test cases is not the only way to gather V&V evidence. IEEE 1012-2024 includes analysis, evaluation, review, inspection, assessment, and testing among its methods. NASA’s systems-engineering guidance also identifies verification by test, analysis, inspection, or demonstration. The suitable method depends on the product, the requirement or need being assessed, and the evidence needed.
A test can be useful for verification when its expected results are tied to approved requirements. It can support validation when the evaluation addresses whether the product is suitable and effective for its intended users or operating context. A test report that records only pass/fail results against requirements may establish conformance without answering whether the product solves the right problem.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What formal standards cover
IEEE 1012-2024 is listed by IEEE as an active standard for system, software, and hardware verification and validation. Its stated scope includes interfaces and reused products, and it describes different integrity levels. The mnemonic about building the product right or building the right product is helpful, but it is not a complete substitute for the standard’s formal processes.
The ISO/IEC/IEEE 29119 series is an internationally agreed set of software-testing standards. The ISO committee page describes its core processes as organizational, management, and dynamic test levels. Teams that need formal process detail should consult the applicable standard and their organization’s or sector’s requirements; public summaries do not replace the standards text.
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