Error Prevention

For a long time the way products handled mistakes was to announce them. Enter a bad value and red text appears. Click something dangerous and a confirmation dialog appears.

The problem is that an announcement always arrives afterward. Telling someone a document is deleted, or that a file went to the wrong people, is not recovery. Confirmation dialogs turned out not to stop much either. By the third time a person sees the same dialog they stop reading it and click through, and the support ticket about the deleted document arrives anyway.

So when usability gets broken into parts, making mistakes hard to make stands as its own concern. It is a different kind of work from writing good warnings.

Find the places where a mistake is possible, then either make the wrong choice unavailable there or make it reversible. Five techniques cover most of it.

1. Narrow the options. A free-text date field accepts 2026-13-45 and then reports an error. A date picker removes the place where a format error could exist at all.
2. Put the default on the safe side. If a new document defaults to private, then the state where the user has touched nothing is also the least dangerous state.
3. Delay destructive actions by one step. Instead of deleting immediately, move the item to a trash that holds it for 30 days. This stops more real mistakes than any single dialog does.
4. Validate while typing. Rather than making someone hunt through seven fields after hitting submit, flag the field the moment focus leaves it.
5. Leave a way back. An undo button available for five seconds after sending means you can remove the confirmation dialog without raising the cost of a slip.

Blocking and speed pull against each other. A dialog at every step reduces mistakes but erodes efficiency for people who use the product daily. The working compromise is to strip confirmation from anything reversible and keep exactly one gate on things that are not. Where recovery is genuinely impossible — deleting an account, disbanding a team — products go further and require typing the team name by hand, because the friction has to be proportional to what cannot be undone. Where first-time users slip overlaps with learnability; where returning users slip overlaps with memorability.

"Rather than a confirmation here, let's build a trash. Nobody reads a dialog they've seen three times."

Move the safeguard from a warning to a reversal.

"Sharing defaults to anyone with the link. That needs to default to private."

A dangerous default means a user who touched nothing can still cause the incident.

"Let's use a date picker instead of a text field. We had twelve format-error tickets this month."

Remove the way to enter it wrong instead of checking it afterward.

At Pagedeck, Theo changed document deletion from immediate to a trash and removed the confirmation dialog entirely. Noa dropped the default sharing scope to private, and set it so confirmation is requested only when the scope is being widened rather than narrowed.