An OTP (one-time password) is a short code — usually 4 to 8 digits — that is valid for a single login or action and expires within minutes. You've seen them as "Your verification code is 123456." They are one of the most common ways sites confirm that you control an email address or phone number.
Why sites use OTPs
Passwords alone can be guessed, reused, or leaked in data breaches. An OTP adds a second proof: even if someone knows your password, they can't log in without the code sent to your inbox or phone in that moment. This is the basis of two-factor authentication (2FA).
The lifecycle of an email OTP
- You enter your email on a signup or login form.
- The site generates a random code, stores a hashed copy, and emails it to you.
- You retrieve the code from your inbox and type it back into the site.
- The site compares it, checks it hasn't expired, and grants access — then the code is invalidated so it can't be reused.
Receiving OTPs without exposing your real email
For throwaway signups and trials, you may not want to attach your personal address. A disposable inbox solves this: it receives the OTP email in seconds, and a good service detects the code automatically so you can copy it in one tap. MailboxTemp highlights one-time codes at the top of the inbox the moment they arrive.
Security tips
- Never share an OTP with anyone who contacts you — legitimate companies never ask for it.
- Watch the clock: codes usually expire in 5–10 minutes, so retrieve them promptly.
- Use disposable inboxes only for accounts you can afford to lose — for important logins, use an address you'll keep so you can still receive future codes.
Try receiving an OTP now
Want to see it in action? Grab a free inbox on the MailboxTemp homepage or read our guide to temporary email for verification.