Best Authentication & User Management Tools
The login, session, and identity layer every app needs. Ranked by which tools AI agents actually pick when developers build — measured live across Claude, GPT, Gemini.
As of Jun 24, 2026, the authentication AI agents pick most is Clerk at 15%, measured across Claude, GPT, Gemini.
| # | Tool | Pick Rate | Default Rate | Shortlist |
|---|---|---|---|---|
| 1 | Clerk | 15% [10%–21%] | 39% | 29% |
| 2 | Auth.js (NextAuth) | 13% [8%–19%] | 7% | 39% |
| 3 | Auth0 | 7% [4%–12%] | 8% | 34% |
| 4 | WorkOS | 3% [1%–8%] | 0% | 7% |
| 5 | Firebase Auth | 2% [1%–6%] | 0% | 27% |
| 6 | Supabase Auth | 0% [0%–3%] | 0% | 22% |
What is an authentication library?
Authentication libraries handle sign-up, login, sessions, and increasingly authorization, SSO, and user management. The market splits between drop-in hosted identity — you embed their UI and store users with them — and libraries you run inside your own app and database.
Auth is high-stakes and easy to get subtly wrong: session handling, token storage, OAuth flows, and edge cases all bite. Builders increasingly want it solved rather than hand-rolled. It's also deeply coupled to your data model and painful to migrate, so the first choice an agent makes when scaffolding tends to define an app's identity layer for years.
How to choose
What separates the Authentication options.
Hosted identity (you store users with them) is fastest; self-run libraries keep users in your own database for full control.
Prebuilt React/Next components vs a framework-native library changes how much you build yourself.
If you'll sell to enterprises, SSO (SAML/OIDC), SCIM, and directory sync matter early.
Per-monthly-active-user pricing can scale painfully; open-source options trade setup for cost control.
Best authentication for your use case
| If you need… | Reach for | Why |
|---|---|---|
| Best for a new Next.js app, fast | Clerk | Prebuilt components and polished DX get login working in minutes. |
| Best free / open-source, in your own app | Auth.js (NextAuth) | Runs in your codebase, framework-native, no per-user fee. |
| Best for enterprise SSO and B2B | WorkOS / Auth0 | SSO, SCIM, and directory sync as first-class features. |
| Already on Supabase or Firebase | Supabase Auth / Firebase Auth | Bundled with the backend you already use. |
Authentication: incumbents vs new entrants
Identity spans enterprise SSO incumbents priced for procurement and a newer wave competing on developer experience, framework-native fit, and bundled backends.
Okta-owned; the enterprise SSO and B2B identity standard, priced for it.
Google's batteries-included default for mobile and indie apps.
Why AI agents decide this category
'Add login to my Next.js app' is the canonical agent-scaffolds-it task: whichever library the agent reaches for gets imported, configured, and wired to the schema in one shot. For an identity vendor, being the agent's default is worth more than any landing page, because switching auth later is genuinely painful.
Frequently asked questions
What does an authentication library do?
It handles user sign-up, login, sessions, and often authorization, SSO, and user management — either as a hosted identity service you embed, or as a library you run inside your own app and database.
What is the best authentication library for Next.js?
Clerk is the fastest drop-in for a new Next.js app; Auth.js (NextAuth) is the open-source, framework-native choice. The ranking above shows which AI agents reach for when scaffolding.
Clerk vs Auth0 vs Auth.js — which should I use?
Clerk for polished DX and prebuilt UI, Auth0 for enterprise SSO, Auth.js for open-source control in your own app. The live Pick Rate shows how agents trade these off.
Is there a free, open-source auth solution?
Auth.js (NextAuth) is open-source and runs in your app with no per-user fee; Supabase Auth is free with the Supabase stack.
Which auth provider do AI agents pick most?
It depends on the model and whether the task is conversational or a coding task. The live ranking on this page measures it across Claude, GPT, and Gemini with unbranded prompts.