Format hints must stay, not appear only on error
Aliases: error-only hint · standing format copy · vanishing rule
What it is
Some interfaces hide format copy until validation fails, then pop a red line under the slot. Once the value is fixed, the line is withdrawn, and the next visit is blank again. A persistent format hint keeps the rule in the same place across empty, typing, valid, and invalid states. Validity is an added color or icon, not the showing and hiding of the whole sentence. The issue is presence, not whether the first telling is before input (that is timing), and not whether the copy is an example or a sentence.
Why it happens
Copy that appears only on error binds “the rule” and “you failed” into one event. Readers receive both messages and often process only the emotional one (I failed), skimming the rule. After a fix the copy vanishes, the rule is unreachable again, and the next fill—or a neighboring field of the same kind—cannot reuse the shape just learned. Persistence splits the rule off the failure event: it is part of the environment, and an error only marks that already-present text. Layout is also calmer—an inserted error that shoves later fields down is read as a page jump; a standing hint does not reflow for right versus wrong.
Where it stops holding
On a one- or two-field surface with a universally known format, standing copy is noise, and appearing on error is cleaner. Very long rules turn the form into a manual; details can live in an expandable “format” control, but that control itself should be standing, not spawned by failure. A success state that replaces the whole rule with green confirmation copy removes the rule again, so the next edit falls back on memory. Screen readers re-read newly inserted error nodes on each check; if the rule is already standing, it is enough to append “invalid,” rather than announcing the entire rule as a new message.
Applying it
- Render format copy in a fixed place beside the field at all times; on failure, change that copy’s state rather than inserting a block that did not exist.
- Do not treat “hide the hint once valid” as a cleanliness tactic; shortness of the sentence should provide quiet, not evaporation after success.
- Park long rules behind a standing “view format” control that can be opened from the empty state, not a link that appears only after failure.
- Verify by walking empty → wrong → right → empty again. The hint should stay put in all four states, with only the valid/invalid mark changing. If the rule vanishes once right, the next empty state forces a guess—the error state is still the only carrier.