Six people, six ways of writing the same number.

Why it matters more than it looks

A number missing its country code is fine until you leave the country, at which point it does not dial. A number stored six different ways is also six different strings, which is why duplicate detection - iOS's and everyone else's - misses pairs that are obviously the same to a human. Normalizing the format is partly cosmetic and partly the thing that makes matching work.

The three rules

1. Add country code

Adds your region's country code to numbers saved without one. The important part is the restraint: it only rewrites a number that validates as a number in your own region. A foreign number stored in local format does not, so it is left alone rather than given a country code that would make it undialable.

2. Add + prefix

Adds a leading plus to numbers that already carry a country code, which is what makes them dial from anywhere. This is a separate rule from the one above on purpose - it never adds a code that is not already there, so it cannot double-prefix a number the first rule has already handled.

3. Normalize grouping

Reformats the digits into your region's standard grouping, so a list of numbers reads consistently. This one changes only presentation - the digits are identical before and after.

Numbers duplicated inside one card

Formatting has a side effect worth knowing about. Once every number is in the same shape, the same mobile number stored twice in one contact - once with dashes, once without - becomes visibly identical. A separate rule collapses those within-contact duplicates, which is the kind of duplication people never notice because it does not create a second contact.

How it stays safe

• All three rules are on by default and individually switchable. Turn any of them off and it stops proposing anything.
• Nothing applies without review. You see the exact before and after for every affected contact and select what applies. You can hide contacts you never want touched.
• Everything is reversible. Applied cleanups are logged in History, and undo restores the exact prior value.
• It all runs on your device. No number is uploaded, and no formatting decision consults a server.

Questions