Used For

• +**Your React app's custom auth breaks every other week** → Auth0 handles login, password resets, and security patches automatically
• +**Users abandon signup because they can't remember another password** → One-click Google/Facebook login gets them in immediately
• +**You're manually managing user permissions across 5 different tools** → Single dashboard controls who sees what across all your apps
• +**Support tickets flooded with 'I forgot my password' daily** → Self-service password resets and magic links cut support load by 80%
• +Organizations feature handles multi-tenant setups - each client gets their own branded login without you building separate systems

Best For

• >Your custom login system got breached and your CEO is freaking out about security
• >You're 3 developers deep trying to build SSO and it's been 6 weeks of hell
• >Hit 10,000 users and password reset emails are eating your support team alive

Not For

• -Solo developers or hobby projects — you'll hit the 7,000 user limit faster than you think and get forced into paid plans
• -Teams wanting something simple — requires actual coding to integrate, not just clicking buttons in a dashboard
• -Budget-conscious startups — the $0.07 per user adds up fast, and one viral signup month will shock you with overages

Pairs With

• *React/Next.js (where you'll spend most time configuring callbacks and handling token refresh)
• *Node.js/Express (to validate the tokens Auth0 sends back and protect your API routes)
• *PostgreSQL (to store user profile data that Auth0 doesn't handle, like app-specific preferences)
• *Stripe (for subscription management since Auth0 only does identity, not billing)
• *Slack (where your team gets alerts about suspicious login attempts and celebrates when SSO finally works)
• *AWS/Vercel (to deploy your app with environment variables for Auth0 secrets)
• *Sentry (to catch the inevitable token expiration errors you didn't handle properly)

The Catch

• !The free tier's 7,000 user limit kills side projects right when they get traction — you'll pay $200+ monthly at 10k users
• !Integration takes 'an hour' for basic stuff, but custom rules and webhooks will eat your week debugging cryptic error messages
• !Post-Okta acquisition, pricing jumped 3x for many users and some custom features got deprecated mid-project

Bottom Line

Turns months of auth headaches into an afternoon of setup, but you'll pay enterprise prices even as a startup.