It’s always bugged me that Notion’s official Zapier integration doesn’t provide a way to retrieve someone’s user ID using their email address. You can only retrieve a user by their ID, but often, all you have is their email address.

The reason for this is probably that Notion’s API doesn’t directly support retrieval of a user by their email address; you can only either list all users, or retrieve a single user by their ID.

Fortunately, Custom Actions provides a workaround, since it can combine API calls with light filtering to pull this off in a single action. It’s dead simple to use, and just requires a single input - the email address of the user whose ID you want to retrieve:

If you don’t want to use the AI Copilot builder in Custom Actions, you can just paste this into the Code box under the Advanced tab:

// Define an async function to retrieve all users in a Notion workspace
export async function getUsersByEmail(params: { email: string }): Promise<{ result: any[] }> {
  // Extract the email from the input object
  const { email } = params;

  // Define the URL for the Notion API endpoint to list all users
  const url = 'https://api.notion.com/v1/users';

  // Use fetchWithZapier to make the API request
  const response = await fetchWithZapier(url, {
    method: 'GET',
    headers: {
      'Notion-Version': '2025-09-03' // Specify the Notion API version
    }
  });

  // Throw an error if the response is not OK
  await response.throwErrorIfNotOk();

  // Parse the JSON response
  const data = await response.json();

  // Filter the users by the provided email address
  const filteredUsers = data.results.filter((user: any) => {
    return user.type === 'person' && user.person.email === email;
  });

  // Return the filtered users in a result property
  return { result: filteredUsers };
}