Telegram's Built-in Phone Number Sharing

[Rajulk985]

How it Works: You submit a phone number to a specialized API (e.g., Twilio Lookup, Nexmo Number Insight, Dexatel Lookup). The API returns information about the number's validity, line type (mobile, landline, VoIP), carrier, and sometimes even its current status (active/inactive).
Legality/Ethics:
Pros: Can prevent users from entering fake numbers upfront, improving data quality. Less intrusive than OTP for a preliminary check.
Cons & Considerations:
Consent: You still need explicit consent from the user to even process their phone number for this lookup. The lookup itself is a form of data processing.
Data Minimization: Only use services that return minimal data necessary for your purpose (e.g., just validity, not full subscriber details).
Third-Party Data Processors: Ensure the API provider is GDPR-compliant and has a robust Data Processing Agreement (DPA) with you.
Not Proof of Ownership: A lookup only confirms the number's validity and type, not that the user currently submitting it is its owner. This method is best combined with OTP for critical validations.

How it Works: Telegram bots can request a user's phone number usa telegram mobile phone number list via a special keyboard button. When the user taps this button, their phone number registered with Telegram is shared with your bot.
Legality/Ethics:
Pros: Very convenient for the user, as they don't have to type it. Telegram handles the underlying consent for sharing their registered number.
Cons & Considerations:
Informed Consent: While the user takes an active step, you must still ensure they understand why you are requesting their number and what you will do with it. Your bot's preceding messages should clearly state the purpose (e.g., "Tap 'Share Phone Number' to receive booking confirmations via SMS").
Context is King: This method is legally sound if the request is clearly contextual and the user understands the benefit. Using it without clear purpose is ethically questionable.
Implicit Validation (Less Recommended for Standalone Use).