🔐 SMS Authentication vs Social App Authentication: Which Is More Reliable?
When choosing a method for identity verification in an online service,
two common options are SMS authentication and social app authentication (e.g., LINE).
Both are convenient, but the information they validate and the level of identity assurance
are significantly different.
This article compares their characteristics and explains which method fits which scenario.
💬 Social App Authentication (e.g., LINE) Is Not Phone Number Verification
Social app authentication allows users to log in using an app they already use,
such as LINE.
However, there is a common misunderstanding:
- LINE requires phone number verification when creating an account
- But the service integrating LINE does not receive the user’s phone number
In other words:
“Logged in with LINE = This person owns this phone number”
is not necessarily true.
Users can change their phone number while keeping the same LINE account,
and some users operate LINE on devices without a SIM card.
📱 SMS Authentication Confirms Actual Ownership of the Phone Number
SMS authentication sends a code to a specific phone number.
If the user receives the SMS, they have proven that
they are the owner (or holder) of that phone number.
This provides a high level of identity assurance,
making SMS a strong method for verifying real-world contact information.
🧩 Comparison: SMS Authentication vs Social App Authentication
| Item | SMS Authentication | Social App Authentication (e.g., LINE) |
|---|---|---|
| What it verifies | Ownership of the phone number | Ownership of the social app account |
| Proof of phone number | ◯ (code delivered to the number) | ✕ (phone number not shared with the service) |
| Identity assurance | High | Medium |
| User convenience | Requires entering a code | High (one-tap login) |
| Internet required | No (delivered via carrier network) | Yes |
| Impact of phone number change | Requires re-verification | Account continues without issues |
| Best suited for | Identity verification, security checks | Notifications, integrations for existing users |
💡 How Should You Use Them?
🔹 For initial identity verification or account creation
➡ SMS authentication is best
It directly verifies ownership of the phone number.
🔹 For notifications and ongoing communication
➡ Combine social app login or integration (e.g., LINE)
This improves usability and user engagement.
🔹 If SMS doesn’t arrive
➡ As explained in Vol.2, voice call authentication is a strong fallback option.
📝 Summary
- Social app authentication is convenient but does not verify phone number ownership
- SMS authentication directly confirms ownership and provides stronger identity assurance
- A hybrid approach—SMS first, social app integration afterward—is the most practical
- Voice call authentication can fill in the gaps when SMS delivery is unreliable
Related Links
- Vol.1: What to Do When an SMS Doesn't Arrive
- Vol.2: Voice Call Authentication as an Alternative
- Xoxzo SMS API Documentation
- Xoxzo Voice API
- Xoxzo OTP API (3 JPY/SMS)
“LINE” is a registered trademark of LINE Yahoo Corporation.
Aiko Yokoyama
Customer Success and Operations
Joined January 2014. Experienced as a clerk in Foreign Trading company, started and maintained an online supplement store. Lived in overseas for 15 years. Looking forward to communicating our customers with the broad view based on those experience.
