How can I retrieve a user’s ID from their email in Supabase to share documents (like Google Docs)?

[kirti737]

Hey everyone! 👋
I’m working on a Google Docs–style app where users can share their documents with others by entering their email addresses. To make this work, I need to get the user ID of the person being shared with (based on their email) so I can give them access to the document.

I’m using Supabase for authentication and database management, but I can’t seem to find the right way to fetch a user’s ID using their email.
Could someone explain the correct way to do this or share how you’ve handled it in your own projects?

[Denoroy737]

Hi Kirti,

Yeah, I ran into the same issue when I was building a similar project.
If you’re using Supabase Auth, you can’t directly query the auth.users table from the client-side for security reasons. But you can do it safely using a Supabase server-side function (like with Supabase Admin API).

Here’s how you can do it 👇

Option 1: Using the Supabase Admin API (server-side only)

import { createClient } from '@supabase/supabase-js'

const supabaseAdmin = createClient(
  process.env.NEXT_PUBLIC_SUPABASE_URL,
  process.env.SUPABASE_SERVICE_ROLE_KEY // Important: Use Service Role key here
)

async function getUserIdByEmail(email) {
  const { data, error } = await supabaseAdmin.auth.admin.getUserByEmail(email)

  if (error) {
    console.error('Error fetching user:', error.message)
    return null
  }

  return data.user?.id || null
}

Then you can use that userId to share the document with them.

---

Option 2: If you store user profiles in a custom table (recommended)
A better long-term approach is to create a profiles table linked to auth.users (via a trigger Supabase provides).
Then you can safely query it from the client:

const { data, error } = await supabase
  .from('profiles')
  .select('id')
  .eq('email', recipientEmail)
  .single()

This way, you don’t need to expose your service role key.

---

TL;DR:

• Use Admin API on the backend if you want to query Supabase Auth users.
• Or, store user info in a public “profiles” table for easy querying from the client.

That’s the cleanest and safest way to handle sharing docs by email.