ENGINEERING NOTE 06 / 50 · SMS
Normalize phone numbers at the input boundary
Keep a canonical international representation internally and format it for each user interface. String length alone cannot establish whether a number is valid or accepted by a target service.
Published by OPEN RAMBO. The engineering patterns and pseudocode illustrate designs, not a documented product API. Numerical examples are illustrative.
Separate country from display
A country selector supplies context for a national-format input. Do not concatenate the country code twice when the pasted number already includes it. Preserve the original user input only where justified and avoid putting it in analytics events.
Validate with maintained metadata
Use a maintained phone-number parser for the relevant runtime, with tests for leading zeros and formatting characters. A syntactically valid number can still be unavailable, recycled or unsupported by a merchant. Label structural validation separately from service eligibility.
Make copy behavior predictable
Copy the exact international number without labels, spaces added for decoration or hidden directional characters. Show a masked preview in support screenshots. Let the customer see whether the target form expects a country code separately before pasting.
Illustrative implementation
input = "+1 (202) 555-0123" # illustrative number
canonical = parse_with_region(input, region="US")
# Validate structure, then check product eligibility separately.Acceptance check
Test pasted international input, local input, Unicode spacing and a separate country selector. Never infer support from parser success.