Functional vs Nonfunctional Requirements: Examples
By SayCraft Team · 2026-08-20 · 10 min read
Functional requirements describe what the system does; nonfunctional requirements describe the quality conditions under which it does it. Write them together for the same workflow: one states the role, action, rule, result, and recovery behavior; the other states the context, measure, and accepted threshold for qualities such as performance, accessibility, security, reliability, or privacy. A login feature without failure and quality conditions is incomplete, while “fast and secure” without context or measurement is not testable. The paired examples below keep uncertain thresholds marked for confirmation instead of presenting borrowed numbers as universal facts.
Paired functional and nonfunctional examples
| Workflow | Functional requirement | Quality requirement |
|---|---|---|
| Project list — performance | An invited client can open the projects they are permitted to review and retry after a load failure. | Context: agreed environment and representative dataset. Measure: time from request to usable list or explicit empty state. Threshold: product and engineering owners must confirm before acceptance. |
| Draft upload | A designer can upload a supported file, see progress, cancel, and retry after failure. | Context: supported devices and test files. Measure: keyboard operation, visible status, and recoverable error. Threshold: every scoped action passes the accessibility test case. |
| Approval — reliability | An invited client can approve the current version once; the record stores actor and version. | Context: repeated or concurrent submit. Measure: authoritative approval records per client/version. Threshold: one record, with subsequent submissions returning the existing result. |
| Account recovery — security | A user can request a time-limited reset without the response revealing whether the account exists. | Context: valid and unknown identifiers. Measure: externally visible response and throttling behavior. Threshold: matches the security policy selected by the responsible owner. |
| Client data request — privacy | An authorized owner can request the supported export or deletion workflow and see its recorded status; failures provide an owned recovery path. | Context: representative account data and approved retention policy. Measure: records included, retained, or deleted plus audit evidence. Threshold: privacy and data owners must confirm before acceptance. |
Context, Measure, Threshold
Context: the environment, data, user, and condition under test Measure: the observable result or measurement method Threshold: the accepted target, including who approved it and when
Do not copy a number from another product and label it “best practice.” Performance, availability, retention, and accessibility targets depend on user need, risk, platform, and operating capacity. If no owner has approved a threshold, write “target to confirm” and keep the evidence gap visible.
Put both types into the SRS template, connect them to user value, and design test cases around the highest-risk conditions.
Turn the document into something testable
Give the live builder one functional outcome plus the relevant quality boundary. Treat unverified thresholds as review questions, not facts.
Frequently asked questions
What is the difference between functional and nonfunctional requirements?
Functional requirements describe system behavior, rules, and outcomes. Nonfunctional requirements describe quality conditions such as performance, accessibility, security, reliability, or privacy in a defined context.
How do I make a nonfunctional requirement testable?
State the context, the measure, and the target or threshold. If the threshold is not yet supported by evidence, label it as a target to confirm rather than a universal fact.