Principle 2 Operable · Guideline 2.2: Enough Time
2.2.6 Timeouts
Users are warned when inactivity can cause data loss.
What this means in practice
The warning belongs at the start of the process, not just before expiry – otherwise it does not help those who work slowly.
Normative wording
The binding text lives at the W3C. What you read here is our own faithful rendering – not a quotation.