- **Clerk** is a hosted auth service with polished prebuilt UI. Free up to 50,000 MAU, then $0.02 per user per month. Fast to set up, expensive to scale. - **Supabase Auth** is bundled with Supabase and integrates directly with Postgres Row Level Security. Free up to 50,000 MAU, then $25/mo Pro which includes 100,000 MAU and charges $0.00325/MAU above that. - **Use Clerk if** you want auth working in an afternoon, you're under 50,000 MAU, and you don't need EU data residency. - **Use Supabase Auth if** you're already on Supabase, you want database-enforced authorization through RLS, or cost at scale matters. - **The migration problem** — most developers start on Clerk and migrate off around 50,000 MAU when the bill hits. Knowing this upfront is the whole point of this article.

## Clerk vs Supabase Auth: The Real Decision in 2026 Every Next.js SaaS has to answer the auth question. In 2026 the two most common answers are Clerk and Supabase Auth. They're both good options. They solve overlapping problems with very different opinions about where your user data should live, what you should have to build yourself, and what you should expect to pay as you grow. This guide gives you the honest version. Not the marketing page version. Pricing at scale, what each one actually does for you, where each one falls short, and a clear framework for picking the one that won't require a painful migration six months from now. All code examples target Next.js 16 and TypeScript.

## What Is Clerk? Clerk is a hosted authentication and user management platform. You install their SDK, drop in their prebuilt React components, and get a complete sign-in flow including profile pages, MFA prompts, organization management, and an admin dashboard. Your users' data lives in Clerk's infrastructure. The integration in a Next.js 16 App Router project looks like this: ```ts // middleware.ts (renamed to proxy.ts in Next.js 16) import { clerkMiddleware, createRouteMatcher } from "@clerk/nextjs/server"; const isProtectedRoute = createRouteMatcher(["/dashboard(.*)"]); export default clerkMiddleware(async (auth, req) => { if (isProtectedRoute(req)) { await auth.protect(); } }); export const config = { matcher: ["/((?!_next|[^?]*\\.(?:html?|css|js)).*)", "/(api|trpc)(.*)"], }; ``` ```tsx // app/sign-in/[[...sign-in]]/page.tsx import { SignIn } from "@clerk/nextjs"; export default function Page() { return ; } ``` That's it. Three files and you have a polished sign-in flow with email, Google, GitHub, and magic links all working. That's the honest best case for Clerk and it's genuinely impressive the first time you see it. **What Clerk gives you:** - Prebuilt sign-in, sign-up, and user profile components - Organizations and team management out of the box - MFA, passkeys, and SSO on paid plans - A hosted dashboard to manage users without writing admin UI - Webhooks for user lifecycle events **What Clerk doesn't give you:** - Your user data in your own database - EU data residency (US only as of 2026) - Predictable cost at scale

## What Is Supabase Auth? Supabase Auth is the bundled authentication layer of the Supabase platform. It's built on the open source GoTrue service and integrates directly with Postgres Row Level Security. If you're already using Supabase for your database, you can add auth without installing anything new. ```ts // lib/supabase.ts import { createClient } from "@supabase/supabase-js"; export const supabase = createClient( process.env.NEXT_PUBLIC_SUPABASE_URL!, process.env.NEXT_PUBLIC_SUPABASE_ANON_KEY! ); ``` ```ts // app/actions/auth.ts "use server"; import { createClient } from "@/lib/supabase-server"; export async function signIn(email: string, password: string) { const supabase = await createClient(); const { data, error } = await supabase.auth.signInWithPassword({ email, password, }); if (error) { return { success: false, error: error.message }; } return { success: true, user: data.user }; } ``` Protecting a route in a Next.js 16 Server Component: ```ts // app/dashboard/page.tsx import { createClient } from "@/lib/supabase-server"; import { redirect } from "next/navigation"; export default async function DashboardPage() { const supabase = await createClient(); const { data: { user } } = await supabase.auth.getUser(); if (!user) { redirect("/sign-in"); } return ; } ``` **What Supabase Auth gives you:** - Email and password, magic links, OAuth, SMS, and anonymous sign-in - Direct integration with Postgres Row Level Security via `auth.uid()` - Sessions and JWT refresh handled automatically - User data in your own Postgres database (or Supabase-hosted Postgres) - Free up to 50,000 MAU, essentially free on Pro **What Supabase Auth doesn't give you:** - Prebuilt UI components as polished as Clerk's - Native SAML/SSO without the paid Supabase add-on - A standalone auth layer if you want to move away from Supabase later

## The Pricing Reality This is where most comparison articles get vague. Here are the real numbers pulled directly from the official pricing pages in June 2026. A note on terminology: Clerk uses **MRU** (monthly retained users — users who return 24+ hours after signing up), not MAU. Supabase uses **MAU**. For most products these numbers will be similar but not identical. | | Clerk | Supabase Auth | |---|---|---| | Free tier | 50,000 MRU | 50,000 MAU | | Pro plan base | $25/mo (or $20/mo annual) | $25/mo | | Included in Pro | 50,000 MRU | 100,000 MAU | | Cost at 100K users | ~$1,025/mo (monthly) | ~$25/mo + $0/auth | | Cost at 500K users | ~$9,025/mo (monthly) | ~$25 + $1,300 = ~$1,325/mo | | Basic org features | Free (up to 20 members, 100 orgs) | Build yourself | | Enhanced org features | $100/mo add-on | Build yourself | | SAML/SSO | $75/mo per enterprise connection (Pro) | $0.015/MAU add-on (50 included on Pro) | | Data location | US only | Your choice of region | **The Clerk numbers explained:** At 100K MRU on the monthly Pro plan: $25 base + 50,000 extra users at $0.02 each = $1,025/mo. The annual plan reduces the base to $20/mo but overages stay at $0.02/MRU. At 500K MRU: $25 + 450,000 × $0.02 = $9,025/mo. **The Supabase numbers explained:** Pro is $25/mo and includes 100,000 MAU. Above that, Supabase charges $0.00325 per MAU, which is dramatically cheaper than Clerk. At 500K MAU: $25 + 400,000 × $0.00325 = ~$1,325/mo. That's still a bill to plan for, but it's 7x less than Clerk at the same scale. One important Supabase note: the free tier pauses inactive projects after one week of inactivity and limits you to 2 active projects. On Pro this limitation is removed. This cost curve is why the most common pattern in 2026 is: start on Clerk, migrate somewhere around the 50,000 user mark when the bill catches engineering attention. Knowing this in advance means you can make the call deliberately rather than reactively.

## The RLS Advantage: Why Supabase Auth Is Different This is the section most comparison articles skip, and it's the most important one for anyone building a multi-tenant SaaS. Row Level Security is a Postgres feature that lets you enforce access control at the database level. Supabase Auth makes this work out of the box by exposing `auth.uid()` inside every Postgres policy. ```sql -- Only users can read their own data create policy "Users can read own data" on public.profiles for select using (auth.uid() = user_id); -- Only org members can read org data create policy "Members can read org data" on public.projects for select using ( auth.uid() in ( select user_id from org_members where org_id = projects.org_id ) ); ``` Once these policies exist, every query your app makes is automatically scoped to the signed-in user. It doesn't matter whether the query comes from a Server Action, a Route Handler, a background job, or a direct SQL client. The database itself refuses cross-tenant queries. Application code can't accidentally leak data because it forgot to add a `where user_id = ?` clause. With Clerk, authorization lives in your application code. You write middleware, you write helper functions, you check `userId` in every query. It works, but it's code you have to write and code that can have bugs. This is genuinely the strongest technical argument for Supabase Auth. If you care about data security at the database level and you're building multi-tenant from day one, RLS plus Supabase Auth is the most robust option available.

## Multi-Tenancy: Organizations and Teams Both Clerk and Supabase Auth support multi-tenant SaaS, but in very different ways. **Clerk Organizations** Clerk ships Organizations as a built-in feature on paid plans. You get org creation, member invitations, role management, and an org switcher component out of the box. ```ts // Get current org in a Server Action "use server"; import { auth } from "@clerk/nextjs/server"; export async function getOrgData() { const { orgId, orgRole } = await auth(); if (!orgId) { return { error: "No active organization" }; } // orgId and orgRole are directly available return { orgId, orgRole }; } ``` The tradeoff: org data lives in Clerk's system, not yours. When you query your own database for org-scoped data, you're using Clerk's `orgId` as a reference key. Your database has no enforcement of that boundary — it's all in your application code. **Supabase Auth + Custom Schema** Supabase Auth gives you identity. The org model is yours to build, but once you build it, RLS enforces it automatically. ```sql -- Your org schema create table organizations ( id uuid primary key default gen_random_uuid(), name text not null, slug text unique not null, created_at timestamptz default now() ); create table org_members ( id uuid primary key default gen_random_uuid(), org_id uuid references organizations(id) on delete cascade, user_id uuid references auth.users(id) on delete cascade, role text not null default 'member', created_at timestamptz default now(), unique(org_id, user_id) ); -- RLS policy: only members can see their org's projects create policy "Org members can read projects" on public.projects for select using ( exists ( select 1 from org_members where org_members.org_id = projects.org_id and org_members.user_id = auth.uid() ) ); ``` Now every query against `projects` is automatically scoped to orgs the user belongs to. No middleware. No application-level checks. The database handles it. The tradeoff: you're building the org model yourself. It's not much code, but it's code you write on day one rather than using a prebuilt UI. For most SaaS products this is the right tradeoff — you control the schema and the access rules instead of depending on Clerk's model.

## Setup Time: Honest Assessment **Clerk:** - Time to working sign-in page: 30 minutes - Time to working org management: 2 hours - What you build: almost nothing, it's all prebuilt **Supabase Auth:** - Time to working sign-in page: 2 to 3 hours - Time to working org management: 1 to 2 days (schema, policies, invitation flow) - What you build: sign-in forms, org management UI, invitation emails The honest answer is that Clerk is faster for the first week. Supabase Auth is faster for the next two years because you're not paying $1,000/mo or dealing with a migration. If you're validating an idea this weekend and just need a sign-in page by Sunday, Clerk wins. If you're building something you intend to grow into a business, the setup cost of Supabase Auth is worth it.

## Data Residency and Compliance This one matters more than developers expect until the first enterprise customer asks about it. **Clerk** stores user data in the United States under the EU-US Data Privacy Framework. As of 2026, there is no option to store user data in a specific EU country or region. If your customers require EU data residency, Clerk cannot deliver it. **Supabase Auth** runs on infrastructure you configure. Supabase lets you choose your database region (EU regions available), so your user data can live in Europe. If you're self-hosting Supabase, you control the hosting entirely. For B2C apps or US-only markets, this doesn't matter much. For B2B SaaS selling to European enterprise customers, this is a real difference that can affect whether you can close deals.

## Migrating from Clerk to Supabase Auth The most common migration in 2026 is Clerk to Supabase Auth around the 50,000 MAU mark. Here's what it actually involves so you can budget for it if you go Clerk first. **What needs to change:** **1. User export.** Clerk lets you export users via their backend API. You'll get email, name, OAuth provider info, and metadata. Password hashes are not exportable (different hashing algorithm). Plan on a bulk import of user data. **2. Password handling.** You can't migrate password hashes from Clerk to Supabase Auth. The two options are: trigger a password reset for every user (clean cutover, more support load) or silently prompt for a new password on first login after the migration (less friction, more complex to implement). **3. Session shape.** Clerk's `auth()` returns `userId`. Supabase Auth's `supabase.auth.getUser()` returns a full user object. Every component and Server Action that reads the current user needs updating. This is the most time-consuming part. **4. Webhooks.** Every service listening to Clerk's `user.created` webhook needs to switch to Supabase Auth's lifecycle hooks. Stripe customer creation, analytics events, welcome emails — map them all before the cutover. **5. UI replacement.** Clerk's `` becomes your own sign-in form. A few days of work for a polished result. **Budget:** For a typical app with 10,000 to 50,000 users and a few OAuth providers, budget two engineer-weeks. It's not a nightmare migration but it's real work.

## When to Use Clerk Clerk makes sense when: - You need auth working today, not next week - You're building a prototype or validating an idea - You expect to stay comfortably under 50,000 MAU - You're B2C with no EU data residency requirements - You want the prebuilt org management UI without building it Clerk does not make sense when: - You're planning for significant scale (100,000+ MAU) - You're selling to EU enterprise customers - You want your user data in your own database - Cost predictability is important to your business model

## When to Use Supabase Auth Supabase Auth makes sense when: - You're already using Supabase for your database - You want database-enforced authorization through RLS - You're building multi-tenant from day one and want the schema to own the access rules - You need EU data residency - Cost at scale matters Supabase Auth doesn't make sense when: - You need enterprise SSO (SAML/SCIM) without the Supabase add-on - You want prebuilt polished auth UI without writing forms - You need to move fast and auth is not your bottleneck

## The Decision Framework One question decides it: **where is your product in six months?** If the answer is "still validating, probably under 10,000 users, might pivot," Clerk is fine. The cost is zero, the setup is fast, and you can always migrate later. If the answer is "growing, B2B, probably crossing 50,000 users, selling to companies," Supabase Auth is the better starting point. The extra week of setup now saves you a two-week migration later and eliminates a compounding monthly bill. The one thing to avoid is picking Clerk because it's faster and not running the cost math at your target scale. A SaaS that reaches 200,000 MAU on Clerk is looking at a $3,000/mo auth bill. That's not a disaster, but it's a very fixable problem you chose not to fix when you had the chance.

## Wrap Up Clerk and Supabase Auth are both solid options. Clerk wins on developer experience and setup speed. Supabase Auth wins on cost at scale, RLS integration, data ownership, and EU data residency. For most Next.js SaaS products being built in 2026 with serious growth ambitions, Supabase Auth is the better long-term foundation. For prototypes, hackathons, and products staying under 50,000 MAU, Clerk is a perfectly reasonable choice. If you're building a SaaS and want your project management, deployment tracking, and analytics in one place so you can focus on product decisions instead of tab switching, check out [AdeptDev](https://adeptdev.io). Free for 7 days.

## What is the difference between Clerk and Supabase Auth? Clerk is a hosted authentication service where user data lives in Clerk's infrastructure. It has polished prebuilt UI components and is fast to set up. Supabase Auth is bundled with Supabase and stores user data in your Postgres database. It integrates directly with Row Level Security, making data access policies enforceable at the database level. Clerk is faster to start. Supabase Auth is cheaper at scale and gives you more control. ## How much does Clerk cost compared to Supabase Auth? Both are free up to 50,000 users (Clerk calls these MRU — monthly retained users; Supabase calls them MAU). Above that, Clerk's Pro plan costs $25/mo base and charges $0.02 per MRU above the included 50,000. At 100,000 MRU that's roughly $1,025/mo. Supabase Pro is $25/mo and includes 100,000 MAU, then charges $0.00325 per MAU above that. At 500,000 users, Clerk costs around $9,025/mo while Supabase costs around $1,325/mo — roughly 7x cheaper at that scale. ## Is Clerk or Supabase Auth better for Next.js? Both work well with Next.js 16. Clerk has a first-party Next.js SDK with prebuilt components that make setup very fast. Supabase Auth requires you to build your own forms but integrates cleanly with Server Actions and Server Components. For most production Next.js SaaS products, Supabase Auth is the better long-term choice because of cost predictability and RLS integration. ## What is Supabase Row Level Security and why does it matter for auth? Row Level Security (RLS) is a Postgres feature that lets you define access control policies directly in the database. Supabase Auth exposes `auth.uid()` inside every RLS policy, so you can write rules like "users can only read their own rows" or "org members can only read their org's data" at the database level. These rules apply to every query regardless of where it comes from. With Clerk, authorization lives in your application code and can have bugs that leak data. ## Can I migrate from Clerk to Supabase Auth? Yes. The migration involves exporting users from Clerk's API, importing them into Supabase Auth, handling password rehashing (since hashes aren't portable between providers), updating session handling code throughout your app, and switching webhooks. For a typical app with 10,000 to 50,000 users, budget two engineer-weeks. It's not a nightmare but it's real work, which is why choosing correctly upfront matters. ## Does Clerk support EU data residency? No. As of 2026, Clerk stores all user data in the United States. They operate under the EU-US Data Privacy Framework but cannot offer EU data residency. If your customers require data to be stored in a specific EU country or region, Clerk cannot meet that requirement. Supabase Auth stores data in whichever Supabase region you choose, including EU regions. ## Should I use Clerk or Supabase Auth for a B2B SaaS? Supabase Auth is generally the better choice for B2B SaaS. It's cheaper at scale, supports EU data residency, and its RLS integration is the strongest data isolation story for multi-tenant products. Clerk is a reasonable choice for B2C apps or products staying under 50,000 MAU. For B2B with enterprise customers, Supabase Auth avoids the pricing shock and data residency limitations that Clerk runs into.