Authentication
Sign-in for your app: logins, passwords, single sign-on. Prices checked 2026-10-20.
What it is, and what decides the price
Authentication is the sign-in part of your app: sign-up, log-in, password reset, social login and, for larger customers, single sign-on. You can build it yourself, rent it from a vendor, or use the one that comes with your database.
Vendors bill by monthly active users (most of them), by retained users (Clerk) or by registered accounts (Skapi), and several are free for tens of thousands of users. What decides the price is usually the features you need on top: multi-factor authentication, a sign-in page on your own domain, single sign-on for business customers. Those are often on a paid plan.
Which one do you pay for today?
Other tools we compare
What each costs at 25,000 monthly users
Cheapest first, for the default use case (4 must-haves). Pick a tool to see its plans, limits and sources, or open a leader above to compare it with the others at every size.
| tool | plan | $/mo | covers |
|---|---|---|---|
| Firebase Authentication | Identity Platform | $0 | all 4 |
| Skapi | Standard | $19 | 1 of 4, the rest not confirmed |
| Clerk | Pro | $25 | all 4 |
| Supabase Auth | Pro | $35 | all 4 |
| WorkOS AuthKit | Pay as you go | $99 | all 4 |
| Kinde | Pro | $278.75 | all 4 |
| Auth0 | Essentials | $2,100 | all 4 |
How we compare
Every user who signs in during the month counts once. Monthly billing, list prices, the cheapest plan that covers the size and everything you need. Clerk counts "retained" users (people who return a day or more after signing up), which is fewer than active users, so its bill can be lower than the same number of active users would suggest. Enterprise-connection, SMS and other metered extras are not included. A blank price means the vendor publishes no price at that size.