Block disposable email in your stack.

Drop a single Route Handler into your Next.js 15 / App Router project. Calls CheckDisposable Email server-side so the API key never reaches the browser. Works with any auth library (Better Auth, NextAuth, Clerk, Supabase).

Add a form validator that calls CheckDisposable Email before saving the user. Works in any Django version (3, 4, 5). Pairs cleanly with django-allauth or Django's built-in auth.

Use a Supabase Edge Function as an Auth Hook. Calls CheckDisposable Email before Supabase creates the user — rejects the signup at the auth layer so no row is ever written to `auth.users`.

Better Auth fires a `databaseHooks.user.create.before` hook for every signup path — email/password, Google OAuth, magic link, anything. Add a single check to this hook and you cover them all.

Use Clerk's `restrictions` API or a webhook on `user.created` to reject disposable signups before they become full Clerk users. Two patterns depending on whether you want to block at the form or at the API.

Use an Auth0 Pre User Registration Action. The Action runs synchronously before Auth0 creates the user — return `api.access.deny()` and the signup is rejected at the auth layer.

Use a Firebase Cloud Function with the `beforeUserCreated` blocking trigger. The function runs synchronously before Firebase persists the user — throw `HttpsError` to reject.

Attach a Lambda to the `PreSignUp` trigger of your Cognito User Pool. The Lambda runs synchronously and can throw to reject before the user record is written.