Login and Verification Flows Customers Can Actually Complete
Sign-up is where many apps lose people. Verification is necessary, but each extra step should earn its place and fail gracefully.
Choose the lightest sign-in that is safe enough
For a café loyalty app, an email link may be enough. For anything handling money or health data, add a second factor. Multi-factor authentication combines something the user knows with something they have.
One-time codes
A one-time password is valid for a single login or transaction. Codes sent by SMS are familiar to customers, but delivery can fail or be delayed, and phone numbers can be taken over. Authenticator apps and passkeys are generally stronger where your customers can use them.
Design for the code that never arrives
- Show how long the code is valid and when a new one can be requested.
- Offer a resend after a short wait, and an alternative channel.
- Explain common causes in plain words: blocked senders, full inboxes, wrong number format.
- Give a clear route to human help.
Learn from good help pages
Support pages written for frustrated users are a useful benchmark for your own error states. One that walks through the problem in order, in Traditional Chinese, is a five-step troubleshooting guide for users who are not receiving SMS verification codes during sign-up, with when to contact support (收不到簡訊驗證碼排查). Its sequence, rules first, then checks, then escalation, is what an in-app error message should follow too.
Account recovery is part of login
Design password reset and lost-phone recovery at the same time as sign-in. Recovery flows are the most common target for account takeover; make them safe as well as easy.
Revised 2026-10-20