Clerk Auth

Clerk's pitch: skip building 6 weeks of auth UI (sign-in, sign-up, password reset, email verification, MFA, invitations, orgs, roles). Free up to 10k MAU. Trade-offs: vendor dependency, opinionated UI surfaces, more expensive at scale than Auth.js.

When to use

• B2B SaaS with teams/orgs/invites — Clerk's Organization model is the killer feature.
• You want sign-in UI in 30 minutes, not 30 hours.
• Compliance posture (SOC2, audit logs) outsourced.
• You'll spend more on engineering hours building auth than Clerk's monthly cost.

When NOT to use

• B2C consumer scale (>100k MAU) where Clerk's pricing curves up — Auth.js + your own DB.
• Strict data residency (must keep all PII on your infra) — self-host (Keycloak) or Auth.js.
• You need deeply custom flows Clerk's hooks don't support.

Core concepts