Add Real User Authentication and Row Level Security to a Supabase App
You'll add real accounts to a Supabase app instead of leaving every table wide open. You'll wire up email and password sign-up and sign-in using the client library. You'll let a visitor start anonymously and upgrade to a full account without losing their data. You'll write Row Level Security policies that only let people see or change rows they actually own. You'll finish with a team-based policy so a group of users can share access to the same data, the same pattern real multi-user apps rely on. By the end you'll have working sign-up, sign-in, and layered access control protecting your data.
Who this is for: Anyone with a Supabase project who wants real user accounts and clear rules for who can see and change what.
By the end, you'll have:
- Working email and password sign-up and sign-in wired to a live Supabase project
- A visitor signed in anonymously, then upgraded to a full account
- A Row Level Security policy that only lets a user see their own rows
- A second policy that only lets a user insert or update rows they own
- A team-based Row Level Security policy that lets a group of users share access to the same data
What you'll learn:
- The difference between authentication and authorization in Supabase
- How to sign up and sign in a user with the client library
- How anonymous sign-in works and how to upgrade an anonymous user to a full account
- How to write using and with check conditions in a Row Level Security policy
- How a team or group-based access pattern works with a junction table
The journey
3 objectives. One real outcome.
Objective 1
Add Email and Password Sign-Up and Sign-In
Wire up email and password sign-up and sign-in using the client library, then confirm the session and inspect the JWT.
Objective 2
Let Anonymous Users Upgrade to Full Accounts
Sign a visitor in anonymously, then upgrade that session to a full email and password account.
Objective 3
Write Row Level Security Policies for Owner and Team Access
Write an owner-only Row Level Security policy, then extend the pattern to a team-based policy using a junction table.
Frequently asked questions
What's the difference between authentication and authorization?
Authentication checks who you are, like signing in. Authorization checks what you're allowed to do once you're signed in, which is what Row Level Security policies control.
Why would I sign a user in anonymously?
It lets someone start using your app right away, like adding items to a cart, without forcing them to create an account first. You can upgrade them to a full account later.
What's the difference between using and with check in a policy?
Using checks a condition against rows that already exist, like what a user can currently see. With check applies to rows after a change happens, like what a user is allowed to insert or update.
Do I need a special table for team-based access?
Yes, typically a junction table that maps each user to the team or group they belong to. Your policy then checks that table to decide what a user can access.
Is Row Level Security the only way to control access in Supabase?
No. Since Supabase issues standard JWTs, you can also verify them yourself on your own backend server if you want authorization logic outside the database.