Use phone-number lookup in a signup flow

Use Lookup to choose a sensible next step after a customer enters a phone number. A number's properties help routing; they do not prove who owns it.

Ask for the country context and show the normalized international number back to the customer. Run the lookup on your server using the TypeScript or Python quickstart.

Store the original input and normalized value in the application record when needed for correction. Avoid silently changing a number into a different customer's destination.

The base result describes the number. Optional properties answer additional questions and have their own status. Read the phone-number guide and pricing before adding properties to every signup request.

For example, use line type to decide which verification options to present. Use a requested risk signal as one input to your application policy. An unavailable property is not evidence that a number is safe or unsafe.

Define three paths in your application: a supported result, a result that requires another route, and an unanswered signal. Tell the customer what they can do next, such as correcting the number or choosing another verification channel.

Keep the original lookup result with the decision so you can explain why the application selected that route. Do not present a carrier or number-format result as proof of customer identity.

Use Verify to check control of the destination when the customer action requires it. Follow the verification application flow to bind the result to signup or recovery.

Exercise malformed input, an unsupported optional property, a provider error and a customer correcting the number. Lookup troubleshooting helps separate these cases.

Lookup resources includes API reference and migration guides.

Build the complete lookup form with Next.js or FastAPI, including phone and email decision paths.