Best auth for SaaS
Last checked Oct 2026In short: For most new SaaS apps, auth costs $0 until you reach 50,000 users: Clerk, Supabase Auth and Firebase Auth all include 50,000 free monthly users. Pick Clerk if you want auth that is quick to set up in a Next.js app, Supabase Auth if you also want a Postgres database, and Firebase Auth if you are already on Google's stack. Prices from the official pricing pages, read Oct 22, 2026. [1] [2] [3]
Ranked by fit, not by commission. We haven't tested these auth tools hands-on; this compares published pricing and our directory notes.
Auth pricing side by side
| Clerk | Supabase Auth | Firebase Auth | |
|---|---|---|---|
| Free users | 50,000 monthly retained users per app (Hobby) [1] | 50,000 monthly active users (Free) [2] | 50K monthly active users (Spark) [3] |
| Paid plan | Pro $25/mo ($20/mo billed annually) [1] | Pro from $25/mo, includes database, storage and functions [2] | Blaze: pay as you go, no monthly fee [3] |
| Users included on paid plan | 50,000 MRU per app [1] | 100,000 MAU [2] | Same 50K MAU no-cost tier [3] |
| Over the limit | $0.02 per MRU per month [1] | $0.00325 per MAU [2] | Google Cloud pricing [3] |
| Watch out | Clerk only counts users who come back after their first day | Free projects pause after 1 week of inactivity | Phone (SMS) sign-in is billed per SMS |
What auth costs as you grow
Worst case: every user counts as monthly active (or retained), auth only, no other usage.
| Users | Clerk | Supabase Auth | Firebase Auth |
|---|---|---|---|
| 1,000 | $0 (Hobby) | $0 (Free) | $0 (Spark) |
| 10,000 | $0 (Hobby) | $0 (Free) | $0 (Spark) |
| 100,000 | $25 Pro + 50,000 × $0.02 = $1,025/mo | $25/mo (Pro includes 100,000 MAU) | 50K free, the rest at Google Cloud pricing [3] |
Our arithmetic from the official per-user rates above. Clerk's figure uses monthly billing; Supabase's $25 includes $10 compute credit. Firebase doesn't publish a per-user rate on its pricing page, so we don't estimate it.
Which to pick
- Clerk: best for Next.js apps that need polished auth set up quickly.
- Supabase Auth: best if you want a Postgres database with auth and storage included. See Supabase vs Clerk.
- Firebase Auth: fits apps already using Firebase. See Supabase vs Firebase pricing.