A default must state its source and remain editable
Aliases: default provenance · inferred default · why this value
What it is
Once a field is prefilled, say where the value came from, and keep it changeable. Source and editability turns a default from “the system already decided” into “this is a suggestion you can replace.” Sources include a timezone guessed from location, the last session, an organisation policy, a query parameter on a shared link. Without a source, a prefill looks like something the user already chose; without edit, a prefill is a lock. Missing either, the default is taken as a fait accompli.
Why it happens
People judge a lit value by “do I remember choosing this.” If they do, they treat it as memory; if they do not, they suspect a change or a miss-tap. A short source line (“from your current location,” “same as last time”) supplies an external attribution, so the prefill is less likely to be mistaken for their own history. Editability then guarantees an action after the attribution: disagree with the suggestion, swap it now, without hunting for a hidden reset.
Source also exposes a wrong inference. Location fills a timezone for the city of a trip; “from your current location” tells them why it is wrong, otherwise the account looks broken. A link parameter preselects a plan; without “from the invite link,” that plan looks like the only plan.
Where it stops holding
When the source is a sensitive inference (home address from a contacts book, options from health data), the explanation itself may be out of bounds, and such defaults often should not exist. Long source copy becomes an unread footnote; compress it to a short, expandable line. An organisation-forced value may be uneditable, but the source must be stronger (“set by an admin”) and must point at who can change it, rather than posing as a personal default. On an autosave settings page, a changed default writes at once; the source line must be visible before that write, or “editable” exists only as a rollback after the fact.
Applying it
- Put a one-line source next to every prefill; a prefill with nothing to say should go back to empty or be marked “example, please choose.”
- Keep the prefilled item as clickable as its peers; do not costume a default in disabled style.
- Forced policy should be read-only plus source, not a default that looks live and does nothing.
- How to check: ask “why this value” and “how do I pick another.” No answer to the first is missing source; a long hunt for the second is missing edit.