Test complete journeys
A contact form, account flow or purchase path must work from entry to confirmation. A visual review cannot prove that data, notifications and error handling behave correctly.
Check real viewport pressure
Long headings, translated content, browser zoom and short mobile screens expose weaknesses that a single desktop screenshot misses.
Protect the next release
Record important checks and repeat them after meaningful changes. Quality assurance is most useful when it becomes part of delivery rather than a final emergency pass.