One number.
Five useful formats.
The right format depends on where your contact list is going. E.164 is a practical default for international lists. Check your destination system’s requirements before importing.
| Format | Example | Use |
|---|---|---|
| E.164 | +442079460018 | Compact international storage |
| International | +44 20 7946 0018 | Human-readable contact lists |
| National | 020 7946 0018 | Within a country; keep country data |
| Phone link | tel:+442079460018 | Phone links, including extensions |
| International digits | 442079460018 | Systems that explicitly require no + |
Choose the country before guessing.
National numbers need a default country. For a mixed-country spreadsheet, map a column with two-letter ISO codes, such as GB, SI or US. An explicit international prefix takes priority. An empty country cell uses your default; an invalid ISO code needs review.
Keep extensions separate.
We accept ext. 123, x123, int. 123 and ;ext=123. Extensions are exported in a separate column because they are not part of E.164. Two numbers with the same base number but different extensions are not marked as duplicates.
Protect leading zeros.
Store phone cells as text in your spreadsheet. If Excel has already removed a zero, no formatter can reliably restore it. Numeric sources get a warning. Text in scientific notation is rejected so rounded or incomplete numbers do not silently enter your list.
Export with confidence.
Excel exports use text cells to preserve + signs and zeros. Spreadsheet-safe CSV adds an apostrophe to values that could be read as formulas, including values beginning with +. Use Excel for exact text, or verify your importing system’s CSV handling.
What “valid” tells you.
A valid result matches the numbering rules in our included metadata. It does not confirm ownership, reachability or consent to contact someone. Short emergency codes, alphabetic numbers and multiple numbers in one cell are outside the standard contact-number workflow.
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