Custom Auth Emails with React Email and Resend

Use the send email hook to send custom auth emails with React Email and Resend in Supabase Edge Functions.

Prefer to jump straight to the code? Check out the example on GitHub.

Prerequisites#

To get the most out of this guide, you’ll need to:

Make sure you have the latest version of the Supabase CLI installed.

1. Create Supabase function#

Create a new function locally:

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supabase functions new send-email

2. Edit the handler function#

Paste the following code into the index.ts file:

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import React from 'npm:react@18.3.1'
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import { Webhook } from 'https://esm.sh/standardwebhooks@1.0.0'
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import { Resend } from 'npm:resend@4.0.0'
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import { renderAsync } from 'npm:@react-email/components@0.0.22'
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import { MagicLinkEmail } from './_templates/magic-link.tsx'
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const resend = new Resend(Deno.env.get('RESEND_API_KEY') as string)
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const hookSecret = (Deno.env.get('SEND_EMAIL_HOOK_SECRET') as string).replace('v1,whsec_', '')
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Deno.serve(async (req) => {
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  if (req.method !== 'POST') {
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    return new Response('not allowed', { status: 400 })
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  }
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  const payload = await req.text()
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  const headers = Object.fromEntries(req.headers)
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  const wh = new Webhook(hookSecret)
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  try {
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    const {
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      user,
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      email_data: { token, token_hash, redirect_to, email_action_type },
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    } = wh.verify(payload, headers) as {
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      user: {
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        email: string
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      }
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      email_data: {
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        token: string
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        token_hash: string
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        redirect_to: string
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        email_action_type: string
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        site_url: string
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        token_new: string
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        token_hash_new: string
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      }
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    }
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    const html = await renderAsync(
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      React.createElement(MagicLinkEmail, {
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        supabase_url: Deno.env.get('SUPABASE_URL') ?? '',
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        token,
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        token_hash,
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        redirect_to,
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        email_action_type,
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      })
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    )
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    const { error } = await resend.emails.send({
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      from: 'welcome <onboarding@resend.dev>',
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      to: [user.email],
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      subject: 'Supa Custom MagicLink!',
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      html,
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    })
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    if (error) {
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      throw error
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    }
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  } catch (error) {
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    console.log(error)
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    return new Response(
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      JSON.stringify({
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        error: {
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          http_code: error.code,
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          message: error.message,
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        },
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      }),
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      {
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        status: 401,
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        headers: { 'Content-Type': 'application/json' },
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      }
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    )
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  }
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  const responseHeaders = new Headers()
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  responseHeaders.set('Content-Type', 'application/json')
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  return new Response(JSON.stringify({}), {
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    status: 200,
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    headers: responseHeaders,
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  })
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})

3. Create React Email templates#

Create a new folder _templates and create a new file magic-link.tsx with the following code:

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import {
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  Body,
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  Container,
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  Head,
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  Heading,
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  Html,
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  Link,
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  Preview,
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  Text,
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} from 'npm:@react-email/components@0.0.22'
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import * as React from 'npm:react@18.3.1'
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interface MagicLinkEmailProps {
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  supabase_url: string
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  email_action_type: string
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  redirect_to: string
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  token_hash: string
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  token: string
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}
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export const MagicLinkEmail = ({
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  token,
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  supabase_url,
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  email_action_type,
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  redirect_to,
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  token_hash,
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}: MagicLinkEmailProps) => (
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  <Html>
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    <Head />
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    <Preview>Log in with this magic link</Preview>
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    <Body style={main}>
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      <Container style={container}>
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        <Heading style={h1}>Login</Heading>
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        <Link
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          href={`${supabase_url}/auth/v1/verify?token=${token_hash}&type=${email_action_type}&redirect_to=${redirect_to}`}
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          target="_blank"
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          style={{
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            ...link,
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            display: 'block',
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            marginBottom: '16px',
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          }}
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        >
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          Click here to log in with this magic link
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        </Link>
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        <Text style={{ ...text, marginBottom: '14px' }}>
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          Or, copy and paste this temporary login code:
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        </Text>
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        <code style={code}>{token}</code>
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        <Text
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          style={{
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            ...text,
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            color: '#ababab',
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            marginTop: '14px',
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            marginBottom: '16px',
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          }}
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        >
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          If you didn&apos;t try to login, you can safely ignore this email.
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        </Text>
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        <Text style={footer}>
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          <Link
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            href="https://demo.vercel.store/"
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            target="_blank"
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            style={{ ...link, color: '#898989' }}
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          >
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            ACME Corp
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          </Link>
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          , the famouse demo corp.
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        </Text>
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      </Container>
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    </Body>
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  </Html>
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)
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export default MagicLinkEmail
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const main = {
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  backgroundColor: '#ffffff',
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}
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const container = {
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  paddingLeft: '12px',
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  paddingRight: '12px',
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  margin: '0 auto',
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}
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const h1 = {
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  color: '#333',
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  fontFamily:
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    "-apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', 'Cantarell', 'Fira Sans', 'Droid Sans', 'Helvetica Neue', sans-serif",
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  fontSize: '24px',
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  fontWeight: 'bold',
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  margin: '40px 0',
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  padding: '0',
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}
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const link = {
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  color: '#2754C5',
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  fontFamily:
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    "-apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', 'Cantarell', 'Fira Sans', 'Droid Sans', 'Helvetica Neue', sans-serif",
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  fontSize: '14px',
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  textDecoration: 'underline',
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}
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const text = {
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  color: '#333',
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  fontFamily:
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    "-apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', 'Cantarell', 'Fira Sans', 'Droid Sans', 'Helvetica Neue', sans-serif",
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  fontSize: '14px',
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  margin: '24px 0',
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}
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const footer = {
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  color: '#898989',
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  fontFamily:
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    "-apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', 'Cantarell', 'Fira Sans', 'Droid Sans', 'Helvetica Neue', sans-serif",
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  fontSize: '12px',
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  lineHeight: '22px',
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  marginTop: '12px',
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  marginBottom: '24px',
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}
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const code = {
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  display: 'inline-block',
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  padding: '16px 4.5%',
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  width: '90.5%',
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  backgroundColor: '#f4f4f4',
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  borderRadius: '5px',
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  border: '1px solid #eee',
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  color: '#333',
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}

You can find a selection of React Email templates in the React Email Examples.

4. Deploy the Function#

Deploy function to Supabase:

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supabase functions deploy send-email --no-verify-jwt

Note down the function URL, you will need it in the next step!

5. Configure the Send Email Hook#

Go to the Auth Hooks section of the Supabase dashboard and create a new "Send Email hook".
Select HTTPS as the hook type.
Paste the function URL in the "URL" field.
Click "Generate Secret" to generate your webhook secret and note it down.
Click "Create" to save the hook configuration.

Store these secrets in your .env file.

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RESEND_API_KEY=your_resend_api_key
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SEND_EMAIL_HOOK_SECRET="v1,whsec_<base64_secret>"

You can generate the secret in the Auth Hooks section of the Supabase dashboard.

Set the secrets from the .env file:

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supabase secrets set --env-file supabase/functions/.env

Now your Supabase Edge Function will be triggered anytime an Auth Email needs to be sent to the user!