nextauthjs/next-auth · error

Unsupported database type

Error message

Unsupported database type (${typeof db}) in Auth.js Drizzle adapter.

What it means

DrizzleAdapter accepts a driver-agnostic drizzle instance and uses instanceof checks (is(db, PgDatabase), BaseSQLiteDatabase, etc.) to dispatch to the right dialect-specific adapter. If the passed object matches none of the known database classes, it throws this error. The typeof db in the message shows the JS type of what you actually passed, which is the main debugging clue.

Solutions

1. Wrap your driver in drizzle() before passing it: DrizzleAdapter(drizzle(postgres(url))).
2. Deduplicate drizzle-orm so only one copy is installed (npm ls drizzle-orm; dedupe/overrides) — multiple copies break instanceof checks.
3. Pass the correct instance for your dialect (PgDatabase, MySqlDatabase, BaseSQLiteDatabase).
4. Check the typeof value in the error message; 'string' means you passed the connection URL directly.

Example fix

// before
const adapter = DrizzleAdapter('postgres://user:pass@localhost/db')
// after
import { drizzle } from 'drizzle-orm/postgres-js'
import postgres from 'postgres'
const adapter = DrizzleAdapter(drizzle(postgres('postgres://user:pass@localhost/db')))

import { is } from 'drizzle-orm'
import { PgDatabase } from 'drizzle-orm/pg-core'
if (!is(db, PgDatabase)) throw new Error('DrizzleAdapter requires a drizzle() database instance')

function isDrizzleDb(db: unknown): db is PgDatabase {
  return is(db, PgDatabase)
}

try {
  const adapter = DrizzleAdapter(db)
} catch (e) {
  if (e instanceof Error && e.message.includes('Unsupported database type')) {
    // typeof in message tells you what you passed; wrap driver in drizzle() or dedupe drizzle-orm
  }
  throw e
}

When it happens

Trigger: Passing something that is not a drizzle database instance: a plain connection string, a raw driver client (e.g. mysql2 pool, postgres.js sql), a Neon/HTTP client not wrapped in drizzle, or an incompatible drizzle version where instanceof checks fail.

Common situations: Forgetting to wrap the driver with drizzle() (e.g. passing postgres(sql) instead of drizzle(sql)), duplicating drizzle-orm versions so instanceof fails across package instances, or passing a mysql2 connection directly.

Understand the failure class

Background: "Must be a positive integer", "Invalid value", "Unsupported": the invalid-argument-value error family, when a library rejects the value you pass — this error's family across 35 libraries.

Related errors

• AccessDenied
• An adapter is required for the WebAuthn provider
• Authenticator not found.
• Authenticator not found.
• Authenticator not found.

AI-assisted analysis of nextauthjs/next-auth@a1a16a5a77 (2026-08-28). Data as JSON: /api/errors/322d12660b78e69e. Report an issue: GitHub.

Appendix: source

Thrown at packages/adapter-drizzle/src/index.ts:42

import { DefaultPostgresSchema, PostgresDrizzleAdapter } from "./lib/pg.js"
import { DefaultSQLiteSchema, SQLiteDrizzleAdapter } from "./lib/sqlite.js"
import { DefaultSchema, SqlFlavorOptions } from "./lib/utils.js"

import type { Adapter } from "@auth/core/adapters"

export function DrizzleAdapter<SqlFlavor extends SqlFlavorOptions>(
  db: SqlFlavor,
  schema?: DefaultSchema<SqlFlavor>
): Adapter {
  if (is(db, MySqlDatabase)) {
    return MySqlDrizzleAdapter(db, schema as DefaultMySqlSchema)
  } else if (is(db, PgDatabase)) {
    return PostgresDrizzleAdapter(db, schema as DefaultPostgresSchema)
  } else if (is(db, BaseSQLiteDatabase)) {
    return SQLiteDrizzleAdapter(db, schema as DefaultSQLiteSchema)
  }

  throw new Error(
    `Unsupported database type (${typeof db}) in Auth.js Drizzle adapter.`
  )
}

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