Clerk vs Auth0 vs Auth.js vs Firebase Auth vs Supabase Auth
Head-to-head comparison of the top 5 authentication services. Trust scores, real pricing, biggest gotchas, and when to choose each.
| Criteria | Clerk | Auth0 | Auth.js | Firebase Auth | Supabase Auth |
|---|---|---|---|---|---|
| Trust Score | 8/10 | 6.8/10 | 7.5/10 | 7.8/10 | 7.8/10 |
| Free Tier | 10K MAU | 25K MAU | Unlimited (open source) | 50K MAU | 50K MAU |
| Paid Starts At | $25/month + $0.02/MAU | $35/month | Free forever | $0.0055/MAU | $25/month (platform) |
| Best For | Best DX, fastest setup | Enterprise compliance | Full control, zero cost | Google Cloud projects | Supabase platform users |
| Biggest Gotcha | US data storage (GDPR risk) | Pricing drift post-Okta | No pre-built UI | GCP ecosystem lock-in | Coupled to Supabase platform |
| DX Rating | 9/10 | 6/10 | 6/10 | 7/10 | 7/10 |
When to choose each
Choose Clerk if you want auth working in 10 minutes with polished UI components. Best for React/Next.js startups. Watch the $0.02/MAU cost at scale.
Choose Auth.js if you want full control, zero recurring cost, and no vendor lock-in. Budget 2-5 days to build auth UI and security hardening. Best for experienced teams.
Choose Firebase Auth if you’re on Google Cloud and want the most generous free tier (50K MAU). Reliable but ties you into the Google ecosystem.
Choose Supabase Auth if you’re using Supabase for your database. The PostgreSQL + Row Level Security integration is uniquely powerful.
Avoid Auth0 for new projects unless you specifically need enterprise compliance (HIPAA, FedRAMP, SAML). Pricing has drifted upward since Okta acquisition.
Cost comparison at scale
| MAU | Clerk | Auth0 | Auth.js | Firebase | Supabase |
|---|---|---|---|---|---|
| 1K | Free | Free | Free | Free | Free |
| 10K | Free | Free | Free | Free | Free |
| 25K | $525 | Free | Free | Free | Free |
| 50K | $1,025 | $240+ | Free | Free | $25 |
| 100K | $2,025 | Custom | Free | $275 | $25 |
Clerk Pro: $25 base + $0.02/MAU. Auth0: Professional tier for roles. Firebase: $0.0055/MAU after 50K. Supabase: Pro tier includes 100K MAU.