StackBest authentication for solo founders
Every app needs login, and building it yourself means password resets, session security, and OAuth edge cases eating weeks you don't have. Auth providers solve that for a monthly fee that usually starts at zero but can quietly balloon once you cross a user threshold. The real comparison is not features, it is where the free tier ends and what each extra user costs after that.
| Tool | Free tier | Paid from | Best for |
|---|---|---|---|
 Clerk$25/mo | $25/mo | Next.js/React solo founders who want polished auth UI shipped today and are unlikely to pass 50k users soon | |
 Auth0$35/mo | $35/mo | Founders selling into enterprises who need the Auth0 brand name and protocol coverage, and who will stay under 25k MAUs for a while | |
 Supabase Auth$25/mo | $25/mo | Founders already on Supabase (like StackTracker's stack) who want auth, database, and storage on one $25 bill | |
 WorkOS$125/mo per enterprise SSO connection | $125/mo per enterprise SSO connection | Founders who want free auth at any realistic scale and only pay when an enterprise customer demands SSO | |
| $25/mo | Early B2B founders under 10k users who want auth, orgs, feature flags, and billing in one $0-25 tool | ||
 Better Auth (self-hosted)$0 | $0 | TypeScript-comfortable founders who want zero MAU costs and full data ownership, and accept owning the maintenance | |
 Firebase Authusage-based from $0.0055/MAU beyond 50k | usage-based from $0.0055/MAU beyond 50k | Mobile-first founders on iOS/Android who want free, reliable auth and do not need enterprise SSO |
If you are already on Supabase, use Supabase Auth: it is bundled at every tier, free plan included (50k MAUs at $0, 100k on Pro), and it keeps users in your own Postgres. Starting fresh on Next.js with no database preference, Clerk's free tier (50k retained users, prebuilt UI) is the fastest path to shipped, at $0 until you scale, then $25/mo.
If an enterprise customer demands SSO, add WorkOS ($125/mo per connection, billed to that customer) or switch to Better Auth to get SSO free at the cost of self-maintenance. Avoid Auth0 unless enterprise buyers require it: the jump from free to $700/mo at 10k MAUs is the worst cliff in the category.
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The fine print, tool by tool
Clerk$25/mo+
Clerk is a hosted auth service built around prebuilt React and Next.js components, so you drop a SignIn component into your app instead of building login screens. Solo founders pick it when they want working auth today and are on a React stack.
$25/mo (Pro, $20/mo billed annually)
50,000 monthly retained users, unlimited apps, 3 dashboard seats, prebuilt sign-in/sign-up UI, social login, magic links. 1-day log retention and only 5 impersonations/month.
Free tier counts monthly retained users, not signups, and new users are free for their first day. Annual billing saves $5/mo on Pro. The trap is add-ons: B2B auth is $100/mo ($85 annual), so a small B2B SaaS realistically pays $125-225/mo, not $25. Clerk billing also adds 0.7% of revenue on top of Stripe fees if you use it.
- + Drop-in React/Next.js components (SignIn, UserButton, OrganizationSwitcher) get auth live in under an hour
- + 50,000 free monthly retained users is the most generous hosted free tier after WorkOS
- + First 24 hours of a new user are free and there is a one-month grace period when you cross a limit, so signup spam does not inflate your bill
- − B2B features (organizations for customers) cost an extra $100/mo on top of Pro, so real B2B starts at $125/mo
- − Overage is $0.02 per retained user beyond 50k, so 100k users costs about $1,025/mo total versus the $25 base plan
Auth0$35/mo+
Auth0 is the incumbent hosted identity platform, now owned by Okta, covering every login protocol and enterprise integration you can name. A solo founder picks it when enterprise buyers expect the Auth0 name on a security questionnaire, not for the price.
$35/mo (B2C Essentials at 500 MAUs)
25,000 MAUs, 1 custom domain, unlimited social connections, passwordless, 5 organizations, 1 enterprise connection, no credit card required.
The cliff is the whole story: free until 25k MAUs, then per-MAU pricing that reaches $700/mo at 10k MAUs on Essentials because paid tiers price from user 1, not from 25k. Yearly billing is 11x monthly (one month free). Extra enterprise SSO connections are $100/mo each and M2M token add-ons run $10-$1,200/mo. Budget for a painful jump or plan a migration before you outgrow free.
- + 25,000 free MAUs with a custom domain included, which most competitors gate behind paid plans
- + Free tier includes one enterprise connection and self-service SSO, rare at $0
- + Supports basically every protocol and identity provider you will ever be asked about, which helps when enterprise customers audit you
- − Paid pricing jumps fast: 10,000 MAUs on B2C Essentials is $700/mo, versus $25/mo for the same users on Kinde or Clerk
- − B2B plans start at $150/mo for Essentials ($2,100/mo at 10k MAUs) and $800/mo for Professional
Supabase Auth$25/mo+
Supabase Auth is the login layer bundled into the Supabase Postgres backend, storing users as rows in your own database. Solo founders pick it when they already run Supabase, because auth then costs nothing extra on the plan they are paying for anyway.
$25/mo (Pro plan, includes database, storage, and auth)
50,000 MAUs, but max 2 active projects and projects pause after 1 week of inactivity. Basic MFA only, 1-hour auth audit log retention.
Best value if you already use Supabase as your database, since auth is effectively free inside the $25 Pro plan. Watch the free tier pause rule and the 2-project cap. Pro includes a $10 compute credit; extra projects add compute cost. 200k MAUs costs roughly $25 + $325 = $350/mo, still cheaper than competitors.
- + Auth is bundled with your Postgres database, so $25/mo covers your entire backend, not just login
- + Cheapest overage in this list at $0.00325 per MAU beyond the 100,000 included on Pro, double what Clerk includes
- + Users live in your own Postgres with row-level security, and the stack is open source, so you can self-host later with no vendor-hosted user store to migrate off
- − No prebuilt hosted UI as polished as Clerk's, and free-tier projects pause after 7 days of inactivity, which kills side projects with sporadic traffic
- − Advanced phone MFA is $75/mo for the first project, and SAML SSO beyond 50 MAUs costs $0.015 per MAU
WorkOS$125/mo per enterprise SSO connection+
WorkOS sells enterprise readiness (SSO, directory sync, audit logs) as paid add-ons and gives away its hosted AuthKit login for the first million users. Solo founders pick it to get free auth at any realistic scale and only start paying when an enterprise deal demands SSO.
$125/mo per enterprise SSO connection (AuthKit itself free to 1M MAUs)
AuthKit is free for the first 1,000,000 MAUs including social login, passkeys, MFA, magic links, and hosted UI. Bot protection (Radar) is a separate product: 1,000 free checks, then $100/mo per 50k checks.
Core auth is genuinely free to 1M MAUs with no card tricks. The money is in enterprise add-ons: $125/mo per SSO connection, $125/mo per directory sync connection, $99/mo custom domain, audit log streaming $125/mo per SIEM connection. Volume discounts on connections only start at 16+.
- + 1 million free MAUs is orders of magnitude beyond every other hosted provider; most solo projects never pay a cent for core auth
- + Hosted AuthKit UI is quick to integrate, comparable to Clerk in setup speed
- + Per-connection SSO pricing ($125/mo) can be passed straight through to the enterprise customer who demands it, and past 1M users pricing is a flat $2,500 per additional million
- − Each enterprise SSO connection is $125/mo and directory sync is another $125/mo per connection, so 5 SSO customers cost $625/mo unless you bill it back to them
- − Custom domain costs $99/mo, a feature Auth0 includes free
Kinde$25/mo+
Kinde bundles auth, B2B organizations, feature flags, and billing into one hosted product with flat plan pricing. Solo founders pick it early in a B2B build to avoid stitching together three separate subscriptions.
$25/mo (Pro)
10,500 MAUs, social login, MFA, 5 B2B organizations, 2 custom roles, 10 feature flags, 1 webhook, 2 environments. No credit card required.
All plans include the same 10,500 MAUs; you pay for features, then per-MAU overage. The trap is scale: overage at $0.0175/MAU makes Kinde one of the priciest options past 50k users. Monthly active organizations beyond 50 cost $0.43-$0.50 each. The 0.7% transaction fee only applies if you use Kinde's billing.
- + Free tier includes MFA and 5 B2B organizations, features Clerk charges $100/mo extra for
- + Feature flags and billing built in, so you can skip a separate LaunchDarkly-style subscription, and users billed through Kinde billing do not count as billable MAUs
- + Simple flat tiers: $25, $75, $250, no per-seat math
- − Only 10,500 free MAUs versus 50k at Clerk, and overage at $0.0175/MAU on Pro means 50k MAUs costs about $716/mo versus $25 on Clerk
- − Free and Pro cap you at 1 enterprise SSO connection; unlimited SSO requires the $75/mo Plus plan, and Kinde billing takes a 0.7% transaction fee on payments it processes (0.5% on Scale)
Better Auth (self-hosted)$0+
Better Auth is an open source TypeScript auth framework that runs inside your own app and stores users in your own database, with an optional paid cloud dashboard on top. Solo founders pick it when they never want a per-user bill and are comfortable owning the auth code themselves.
$0 (open source); optional cloud dashboard Pro at $20/mo
The framework is fully free and open source with no MAU limits ever. Optional cloud Starter tier adds 1 dashboard seat, 10k audit logs/month with 1-day retention, and 1k security detections/month.
The framework has no pricing at all; costs are your database and an email provider like Resend (~$0-20/mo). The optional cloud product is $0 (Starter) or $20/mo (Pro) for dashboards, audit logs, and self-service SSO with 1 connection included, then $50/mo per extra SSO connection. That is still less than half of WorkOS's $125 per connection.
- + Zero per-user cost forever; 500k users costs the same as 50: your database bill
- + Users stay in your own database, so no migration risk and no vendor to outgrow, and Vercel's backing lowers abandonment risk
- + SSO, SAML, and multi-tenancy plugins are free, versus $100-125/mo per connection at hosted providers, with 50+ plugins covering passkeys, 2FA, orgs, and Stripe
- − You own security patching, session storage, and email delivery; a mistake in your auth code is on you, not a vendor's SLA
- − No hosted UI or dashboard by default; user management screens are yours to build or you pay $20/mo for the cloud dashboard, plus a separate email provider
Firebase Authusage-based from $0.0055/MAU beyond 50k+
Firebase Auth is Google's login service inside the Firebase mobile backend, with SDKs that handle sign-in, account linking, and sessions on iOS and Android. Solo founders pick it for mobile apps where the native SDKs and 50k free users matter more than a web dashboard.
usage-based from $0.0055/MAU beyond 50k (Identity Platform rates)
50,000 MAUs free for email/password and social sign-in, no payment method required. SAML/OIDC free for only 50 MAUs. Phone auth billed per SMS from the start.
Standard auth is free to 50k MAUs, then Blaze plan billing at Identity Platform rates: $0.0055/MAU (50k-100k), $0.0046 (100k-1M). 100k MAUs costs about $275/mo. The traps are per-SMS phone auth charges with no free allowance and the tiny 50-MAU free limit for SAML/OIDC. Set a GCP budget alert before enabling phone sign-in.
- + 50,000 free MAUs and the cheapest hosted overage after Supabase: $0.0055/MAU for 50k-100k, dropping to $0.0046 up to 1M
- + Best-in-class mobile SDKs for iOS, Android, and React Native/Expo, with Google-scale reliability and a 99.95% SLA on the paid Identity Platform tier
- + Anonymous auth and easy account linking are built in and free
- − SMS phone verification is billed per message even on the free plan (roughly $0.01-$0.34 per SMS by country), and a bot attack on phone sign-in can generate a surprise bill
- − SAML/OIDC free tier is only 50 MAUs, then $0.015 per MAU via Identity Platform
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