Input guide
How to format a phone number in E.164
E.164 is the international phone-number format used by WA Lookup requests. A normalized identifier begins with +, includes the country calling code, contains digits only after the plus sign, and does not include spaces, brackets, or a domestic trunk prefix.
Reviewed July 21, 2026
What is a valid E.164 input?
Use + followed by the country calling code and the subscriber number, with no spaces or punctuation—for example, +14155552671. Do not simply prepend a country code to an unchanged local number: remove formatting and any domestic-only trunk prefix according to that country's numbering rules first.
Normalize the number before verification
Treat normalization as its own data step. Preserve the original input for audit, but send only the normalized value to the checker.
- 1
Determine the country
Use a trusted country field or explicit user selection. Do not guess solely from a local-looking number when the source can contain multiple countries.
- 2
Remove presentation characters
Delete spaces, hyphens, parentheses, and dots. These help people read a number but are not part of the normalized identifier.
- 3
Apply national numbering rules
Remove a domestic trunk prefix only when the country's numbering plan requires it for international form.
- 4
Add + and the calling code
Produce one canonical value and validate it before sending the request.
Examples and common corrections
The correct transformation depends on the country context. These examples illustrate formatting patterns rather than replacing a numbering-plan library.
| Input | Normalized example | Reason |
|---|---|---|
| +1 (415) 555-2671 | +14155552671 | Keep country code 1 and remove presentation punctuation. |
| 415-555-2671 with country=US | +14155552671 | Use the explicit country context before adding the calling code. |
| 0044 20 7946 0958 | +442079460958 | Convert the international access prefix 00 to +. |
| +44 (0)20 7946 0958 | +442079460958 | The parenthesized domestic trunk 0 is not retained in international form. |
| 14155552671 | Needs country context | A digits-only value without + is ambiguous unless the source contract defines its country. |
Examples are illustrative. Validate against an up-to-date numbering-plan library when importing data from multiple countries.
Reject ambiguous or unsafe transformations
A syntactically plausible number is not necessarily assigned, reachable, or owned by the expected person. Normalization should improve consistency without inventing missing context.
- Do not remove leading digits unless a country-specific rule identifies a trunk prefix.
- Do not treat +, 00, and a local 0 as interchangeable without country context.
- Do not store several display variants as different contacts after they normalize to the same value.
- Do not interpret successful formatting as WhatsApp registration; formatting only prepares the input.
API input checklist
Before calling the API, confirm that the identifier is one canonical string and that your workflow can trace it back to the original record.
- The value starts with + and contains digits only after it.
- The country calling code came from explicit or reliable context.
- The national number was transformed according to that country's rules.
- Duplicates were compared using the normalized value.
- The original input remains available for correction and audit.