Better Auth vs Supabase Auth for SvelteKit
Better Auth and Supabase Auth both answer the same question in a SvelteKit project: how do users sign in? Open source TypeScript auth library that keeps sessions and users in your own database, extended through plugins. Auth that ships inside Supabase, with users stored in your Postgres and row level security wired to the session. The real split is ownership: Better Auth runs inside your project and leaves the operational work with you, while Supabase Auth runs the hard parts as a service and takes a dependency in exchange.
Verdict
The real split is ownership: Better Auth runs inside your project and leaves the operational work with you, while Supabase Auth runs the hard parts as a service and takes a dependency in exchange. For SvelteKit specifically, both are supported, so let the tradeoff above decide rather than the framework.
Pick Better Auth if
- ✓User and session tables sit in your database, so joins are ordinary SQL.
- ✓Plugin system covers passkeys, two factor and organizations without vendor lock-in.
- ✓Fully typed API surface, so misuse usually shows up at compile time.
Pick Supabase Auth if
- ✓The user table is a Postgres table, so foreign keys to it just work.
- ✓Row level security policies read the session directly, pushing authorization into the database.
- ✓One vendor for auth, storage and database keeps the moving parts low.
| Comparison | Better Auth | Supabase Auth |
|---|---|---|
| Pricing shape | Free and open source. You pay only for the database and server it runs on. | Included with the Supabase project you already pay for, with additional cost only at higher active-user tiers. |
| Frameworks | Next.js, SvelteKit, Nuxt, Expo | Next.js, SvelteKit, Nuxt, React Native, Expo, Flutter |
| In one line | Open source TypeScript auth library that keeps sessions and users in your own database, extended through plugins. | Auth that ships inside Supabase, with users stored in your Postgres and row level security wired to the session. |
Pricing described qualitatively because published plans change often. Checked 2026-08-23. Confirm current terms on Better Auth and Supabase Auth.
Better Auth
Strengths
- ✓User and session tables sit in your database, so joins are ordinary SQL.
- ✓Plugin system covers passkeys, two factor and organizations without vendor lock-in.
- ✓Fully typed API surface, so misuse usually shows up at compile time.
- ✓No per-user cost, which makes free tiers and large user bases cheap.
Tradeoffs
- ✗You run and patch the auth code yourself, including security updates.
- ✗Login screens are your responsibility, since the library ships logic not UI.
- ✗Younger project, so APIs still move and older guides go stale quickly.
- ✗Compliance evidence like SOC 2 covers your infrastructure, not a vendor's.
Supabase Auth
Strengths
- ✓The user table is a Postgres table, so foreign keys to it just work.
- ✓Row level security policies read the session directly, pushing authorization into the database.
- ✓One vendor for auth, storage and database keeps the moving parts low.
- ✓Client libraries for web and mobile share the same session model.
Tradeoffs
- ✗Bundled with Supabase, so adopting it usually means adopting the whole platform.
- ✗Auth schema lives in a managed namespace you cannot freely reshape.
- ✗Row level security is powerful but easy to get subtly wrong.
- ✗Self-hosting the full stack to escape the cloud is a real operations project.
Same pair, different context
Frequently asked questions
Is Better Auth or Supabase Auth better in a SvelteKit project?
Neither is better in the abstract. The real split is ownership: Better Auth runs inside your project and leaves the operational work with you, while Supabase Auth runs the hard parts as a service and takes a dependency in exchange. Decide on the tradeoff you can live with, then stop reading comparisons and ship.
What is the main drawback of Better Auth?
You run and patch the auth code yourself, including security updates. Login screens are your responsibility, since the library ships logic not UI.
What is the main drawback of Supabase Auth?
Bundled with Supabase, so adopting it usually means adopting the whole platform. Auth schema lives in a managed namespace you cannot freely reshape.
Do Better Auth and Supabase Auth both support SvelteKit?
Yes, both list support for SvelteKit, which is why this comparison exists as a SvelteKit page. SvelteKit moved fast enough that training data contains three incompatible generations of it: Sapper, SvelteKit 1.0, and SvelteKit 2 on Svelte 5.