In the modern digital world, mobile apps often require a fast, reliable, and secure way to verify a user’s identity during signup, login, or transaction processes. One of the most common methods for this is OTP (One-Time Password) verification via mobile numbers. This approach involves sending a temporary code to the user’s phone number and asking the user to enter it back into the app to confirm their ownership of that number.
What Is an OTP?
An OTP (One-Time Password) is a numeric or alphanumeric code, usually between 4 and 8 digits, generated randomly and sent to a user’s mobile phone as a verification mechanism. The key properties of OTPs are:
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One-time use: Each code is valid for only a single verification attempt.
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Time-sensitive: OTPs expire after a short period (usually a few minutes).
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Randomness: OTPs are randomly generated to prevent guessing or brute-force attacks.
Why Do Apps Use OTP Verification via Mobile Numbers?
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Verify User Identity: OTPs prove that the user has access to the claimed mobile number.
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Prevent Fraud and Fake Accounts: OTP verification stops bots and fake users from creating multiple accounts.
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Enhance Security: OTPs add a recent mobile phone number data layer of authentication beyond username and password.
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Simplify User Experience: Users don’t have to remember complex passwords—just the code sent to their phone.
Step-by-Step Process of OTP Verification via Mobile Numbers
1. User Inputs Mobile Number
During signup or login, the user enters their but my passion for all mobile number into the app interface.
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This number is usually formatted with a country code to support international users.
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The app checks if the number is valid (correct format, length).
2. App Requests OTP Generation
The app sends the mobile number to a backend server or an SMS gateway service to generate an OTP.
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The backend system creates a random numeric OTP.
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The OTP is stored temporarily in a database, linked to the mobile number, along with a timestamp.
3. Sending OTP to User’s Mobile Number
The backend uses an SMS gateway or telecom service provider to send the OTP via SMS to the user’s phone.
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This process involves API calls to facebook users third-party SMS providers like Twilio, Nexmo, or local carriers.
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The SMS usually contains a short message like: “Your verification code is 123456.”
4. User Receives OTP and Enters It
The user gets the SMS on their phone and enters the OTP into the app’s verification screen.
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On some platforms (especially Android), apps can automatically read the incoming SMS (with permission) and pre-fill the OTP to improve user experience.
5. App Sends OTP Back to Server for Verification
The app sends the entered OTP and mobile number back to the backend server.
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The server checks if the OTP matches the one generated for that number.
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It also checks if the OTP has not expired (usually a few minutes).
6. Verification Success or Failure
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If the OTP matches and is within the valid time window, the server confirms successful verification.
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If the OTP is incorrect, expired, or previously used, verification fails.
Technologies Involved
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SMS Gateway APIs: Services like Twilio, Plivo, or local telecom APIs facilitate reliable SMS delivery worldwide.
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Backend Server Logic: Generates OTPs, stores them securely, and handles verification requests.
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Mobile App SDKs: Some platforms provide native support for auto-reading OTP SMS to ease the user experience.
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Secure Storage: OTPs are temporarily stored in encrypted form to prevent unauthorized access.