← DictionaryTwo-Factor Authentication
also called MFA, two-step verification
Requiring a second proof of identity in addition to a password.
A code as well as a password.
What It Is
You will find Two-Factor Authentication in the Technology layer, alongside the rest of Security. What it actually refers to is requiring a second proof of identity in addition to a password.
It is a mechanism rather than an opinion: set up properly it behaves predictably, and set up badly it fails just as predictably. Once it is defined that clearly, arguments about it usually stop.
How It's Used
Most of the time Two-Factor Authentication is used in build decisions, tooling and the plumbing behind a working system. It is usually discussed together with Security, Password Manager and Domain Ownership. The practical test is whether it is configured, documented and actually working.
Why It Matters
Ignoring Two-Factor Authentication rarely fails loudly — it fails slowly. When it is unclear, small technical debts compound into a rebuild. It is worth pinning down before anyone builds on top of it.
Think of plumbing. Nobody admires it, everybody notices when it leaks. A code as well as a password.
Termshift™
How the meaning shifts depending on who is using it, and where.
Practitioners use Two-Factor Authentication as shorthand and expect no explanation — requiring a second proof of identity in addition to a password.
Outside the industry, most people would just say: a code as well as a password.
The Bottom Line
If you only keep one thing about Two-Factor Authentication: a code as well as a password. Everything after that is detail.