supabase/apps/docs/content/guides/auth/auth-mfa.mdx

---
id: 'auth-mfa'
title: 'Multi-Factor Authentication'
description: 'Add an additional layer of security to your apps with Supabase Auth multi-factor authentication.'
---

Multi-factor authentication (MFA), sometimes called two-factor authentication (2FA), adds an additional layer of security to your application by verifying their identity through additional verification steps.

It is considered a best practice to use MFA for your applications.

Users with weak passwords or compromised social login accounts are prone to malicious account takeovers. These can be prevented with MFA because they require the user to provide proof of both of these:

- Something they know.
  Password, or access to a social-login account.
- Something they have.
  Access to an authenticator app (a.k.a. TOTP) or a mobile phone.

## Overview

Supabase Auth implements MFA via two methods: App Authenticator, which makes use of a Time based-one Time Password, and phone messaging, which makes use of a code generated by Supabase Auth.

Applications using MFA require two important flows:

1. **Enrollment flow.**
   This lets users set up and control MFA in your app.
2. **Authentication flow.**
   This lets users sign in using any factors after the conventional login step.

Supabase Auth provides:

- **Enrollment API** - build rich user interfaces for adding and removing factors.
- **Challenge and Verify APIs** - securely verify that the user has access to a factor.
- **List Factors API** - build rich user interfaces for signing in with additional factors.

You can control access to the Enrollment API as well as the Challenge and Verify APIs via the Supabase Dashboard. A setting of `Verification Disabled` will disable both the challenge API and the verification API.

These sets of APIs let you control the MFA experience that works for you. You can create flows where MFA is optional, mandatory for all, or only specific groups of users.

Once users have enrolled or signed-in with a factor, Supabase Auth adds additional metadata to the user's access token (JWT) that your application can use to allow or deny access.

This information is represented by an [Authenticator Assurance Level](https://pages.nist.gov/800-63-3-Implementation-Resources/63B/AAL/), a standard measure about the assurance of the user's identity Supabase Auth has for that particular session. There are two levels recognized today:

1. **Assurance Level 1: `aal1`**
   Means that the user's identity was verified using a conventional login method
   such as email+password, magic link, one-time password, phone auth or social
   login.
2. **Assurance Level 2: `aal2`**
   Means that the user's identity was additionally verified using at least one
   second factor, such as a TOTP code or One-Time Password code.

This assurance level is encoded in the `aal` claim in the JWT associated with the user. By decoding this value you can create custom authorization rules in your frontend, backend, and database that will enforce the MFA policy that works for your application. JWTs without an `aal` claim are at the `aal1` level.

## Adding to your app

Adding MFA to your app involves these four steps:

1. **Add enrollment flow.**
   You need to provide a UI within your app that your users will be able to set-up
   MFA in. You can add this right after sign-up, or as part of a separate flow in
   the settings portion of your app.
2. **Add unenroll flow.**
   You need to support a UI through which users can see existing devices and unenroll
   devices which are no longer relevant.
3. **Add challenge step to login.**
   If a user has set-up MFA, your app's login flow needs to present a challenge
   screen to the user asking them to prove they have access to the additional
   factor.
4. **Enforce rules for MFA logins.**
   Once your users have a way to enroll and log in with MFA, you need to enforce
   authorization rules across your app: on the frontend, backend, API servers or
   Row-Level Security policies.

The enrollment flow and the challenge steps differ by factor and are covered on a separate page. Visit the [Phone](/docs/guides/auth/auth-mfa/phone) or [App Authenticator](/docs/guides/auth/auth-mfa/totp) pages to see how to add the flows for the respective factors. You can combine both flows and allow for use of both Phone and App Authenticator Factors.

### Add unenroll flow

The unenroll process is the same for both Phone and TOTP factors.

An unenroll flow provides a UI for users to manage and unenroll factors linked to their accounts. Most applications do so via a factor management page where users can view and unlink selected factors.

When a user unenrolls a factor, call `supabase.auth.mfa.unenroll()` with the ID of the factor. For example, call:

```js
import { createClient } from '@supabase/supabase-js'
const supabase = createClient(
  'https://your-project-id.supabase.co',
  'sb_publishable_... or anon key'
)

// ---cut---
supabase.auth.mfa.unenroll({ factorId: 'd30fd651-184e-4748-a928-0a4b9be1d429' })
```

to unenroll a factor with ID `d30fd651-184e-4748-a928-0a4b9be1d429`.

### Enforce rules for MFA logins

Adding MFA to your app's UI does not in-and-of-itself offer a higher level of security to your users. You also need to enforce the MFA rules in your application's database, APIs, and server-side rendering.

Depending on your application's needs, there are three ways you can choose to enforce MFA.

1. **Enforce for all users (new and existing).**
   Any user account will have to enroll MFA to continue using your app.
   The application will not allow access without going through MFA first.
2. **Enforce for new users only.**
   Only new users will be forced to enroll MFA, while old users will be encouraged
   to do so.
   The application will not allow access for new users without going through MFA
   first.
3. **Enforce only for users that have opted-in.**
   Users that want MFA can enroll in it and the application will not allow access
   without going through MFA first.

#### Example: React

Below is an example that creates a new `UnenrollMFA` component that illustrates the important pieces of the MFA enrollment flow. Note that users can only unenroll a factor after completing the enrollment flow and obtaining an `aal2` JWT claim. Here are some points of note:

- When the component appears on screen, the `supabase.auth.mfa.listFactors()` endpoint
  fetches all existing factors together with their details.
- The existing factors for a user are displayed in a table.
- Once the user has selected a factor to unenroll, they can type in the `factorId` and click **Unenroll**
  which creates a confirmation modal.

<Admonition type="note">

Unenrolling a factor will downgrade the assurance level from `aal2` to `aal1` only after the refresh interval has lapsed. For an immediate downgrade from `aal2` to `aal1` after enrolling one will need to manually call `refreshSession()`

</Admonition>

```tsx
/**
 * UnenrollMFA shows a simple table with the list of factors together with a button to unenroll.
 * When a user types in the factorId of the factor that they wish to unenroll and clicks unenroll
 * the corresponding factor will be unenrolled.
 */
export function UnenrollMFA() {
  const [factorId, setFactorId] = useState('')
  const [factors, setFactors] = useState([])
  const [error, setError] = useState('') // holds an error message

  useEffect(() => {
    ;(async () => {
      const { data, error } = await supabase.auth.mfa.listFactors()
      if (error) {
        throw error
      }

      setFactors([...data.totp, ...data.phone])
    })()
  }, [])

  return (
    <>
      {error && <div className="error">{error}</div>}
      <tbody>
        <tr>
          <td>Factor ID</td>
          <td>Friendly Name</td>
          <td>Factor Status</td>
          <td>Phone Number</td>
        </tr>
        {factors.map((factor) => (
          <tr>
            <td>{factor.id}</td>
            <td>{factor.friendly_name}</td>
            <td>{factor.factor_type}</td>
            <td>{factor.status}</td>
            <td>{factor.phone}</td>
          </tr>
        ))}
      </tbody>
      <input type="text" value={verifyCode} onChange={(e) => setFactorId(e.target.value.trim())} />
      <button onClick={() => supabase.auth.mfa.unenroll({ factorId })}>Unenroll</button>
    </>
  )
}
```

#### Database

Your app should sufficiently deny or allow access to tables or rows based on the user's current and possible authenticator levels.

<Admonition type="caution">

Postgres has two types of policies: permissive and restrictive. This guide uses restrictive policies. Make sure you don't omit the `as restrictive` clause.

</Admonition>

##### Enforce for all users (new and existing)

If your app falls under this case, this is a template Row Level Security policy you can apply to all your tables:

```sql
create policy "Policy name."
  on table_name
  as restrictive
  to authenticated
  using ((select auth.jwt()->>'aal') = 'aal2');
```

- Here the policy will not accept any JWTs with an `aal` claim other than
  `aal2`, which is the highest authenticator assurance level.
- **Using `as restrictive` ensures this policy will restrict all commands on the
  table regardless of other policies!**

##### Enforce for new users only

If your app falls under this case, the rules get more complex. User accounts created past a certain timestamp must have a `aal2` level to access the database.

```sql
create policy "Policy name."
  on table_name
  as restrictive -- very important!
  to authenticated
  using
    (array[(select auth.jwt()->>'aal')] <@ (
       select
         case
           when created_at >= '2022-12-12T00:00:00Z' then array['aal2']
           else array['aal1', 'aal2']
         end as aal
       from auth.users
       where (select auth.uid()) = id));
```

- The policy will accept both `aal1` and `aal2` for users with a `created_at`
  timestamp prior to 12th December 2022 at 00:00 UTC, but will only accept
  `aal2` for all other timestamps.
- The `<@` operator is PostgreSQL's ["contained in"
  operator.](https://www.postgresql.org/docs/current/functions-array.html)
- **Using `as restrictive` ensures this policy will restrict all commands on the
  table regardless of other policies!**

##### Enforce only for users that have opted-in

Users that have enrolled MFA on their account are expecting that your
application only works for them if they've gone through MFA.

```sql
create policy "Policy name."
  on table_name
  as restrictive -- very important!
  to authenticated
  using (
    array[(select auth.jwt()->>'aal')] <@ (
      select
          case
            when count(id) > 0 then array['aal2']
            else array['aal1', 'aal2']
          end as aal
        from auth.mfa_factors
        where ((select auth.uid()) = user_id) and status = 'verified'
    ));
```

- The policy will only accept only `aal2` when the user has at least one MFA
  factor verified.
- Otherwise, it will accept both `aal1` and `aal2`.
- The `<@` operator is PostgreSQL's ["contained in"
  operator.](https://www.postgresql.org/docs/current/functions-array.html)
- **Using `as restrictive` ensures this policy will restrict all commands on the
  table regardless of other policies!**

### Server-Side Rendering

<Admonition type="tip">

When using the Supabase JavaScript library in a server-side rendering context, make sure you always create a new object for each request! This will prevent you from accidentally rendering and serving content belonging to different users.

</Admonition>

It is possible to enforce MFA on the Server-Side Rendering level. However, this can be tricky do to well.

You can use the `supabase.auth.mfa.getAuthenticatorAssuranceLevel()` and `supabase.auth.mfa.listFactors()` APIs to identify the AAL level of the session and any factors that are enabled for a user, similar to how you would use these on the browser.

However, encountering a different AAL level on the server may not actually be a security problem. Consider these likely scenarios:

1. User signed-in with a conventional method but closed their tab on the MFA
   flow.
2. User forgot a tab open for a very long time. (This happens more often than
   you might imagine.)
3. User has lost their authenticator device and is confused about the next
   steps.

We thus recommend you redirect users to a page where they can authenticate using their additional factor, instead of rendering a HTTP 401 Unauthorized or HTTP 403 Forbidden content.

### APIs

If your application uses the Supabase Database, Storage or Edge Functions, just using Row Level Security policies will give you sufficient protection. In the event that you have other APIs that you wish to protect, follow these general guidelines:

1. **Use a good JWT verification and parsing library for your language.**
   This will let you securely parse JWTs and extract their claims.
2. **Retrieve the `aal` claim from the JWT and compare its value according to
   your needs.**
   If you've encountered an AAL level that can be increased, ask the user to
   continue the login process instead of logging them out.
3. **Use the `https://<project-ref>.supabase.co/rest/v1/auth/factors` REST
   endpoint to identify if the user has enrolled any MFA factors.**
   Only `verified` factors should be acted upon.

## Frequently asked questions

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  justified
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<AccordionItem
header={<span className="text-foreground">How do I check when a user went through MFA?</span>}
id="how-do-i-check-when-a-user-went-through-mfa"
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Access tokens issued by Supabase Auth contain an `amr` (Authentication Methods Reference) claim. It is an array of objects that indicate what authentication methods the user has used so far.

For example, the following structure describes a user that first signed in with a password-based method, and then went through TOTP MFA 2 minutes and 12 seconds later. The entries are ordered most recent method first!

```json
{
  "amr": [
    {
      "method": "totp",
      "timestamp": 1666086056
    },
    {
      "method": "password",
      "timestamp": 1666085924
    }
  ]
}
```

Use the `supabase.auth.mfa.getAuthenticatorAssuranceLevel()` method to get easy access to this information in your browser app.

You can use this Postgres snippet in RLS policies, too:

```sql
jsonb_path_query((select auth.jwt()), '$.amr[0]')
```

- [`jsonb_path_query(json, path)`](https://www.postgresql.org/docs/current/functions-json.html#FUNCTIONS-JSON-PROCESSING-TABLE)
  is a function that allows access to elements in a JSON object according to a
  [SQL/JSON
  path](https://www.postgresql.org/docs/current/functions-json.html#FUNCTIONS-SQLJSON-PATH).
- `$.amr[0]` is a SQL/JSON path expression that fetches the most recent
  authentication method in the JWT.

Once you have extracted the most recent entry in the array, you can compare the `method` and `timestamp` to enforce stricter rules. For instance, you can mandate that access will be only be granted on a table to users who have recently signed in with a password.

Currently recognized authentication methods are:

- `oauth` - any OAuth based sign in (social login).
- `password` - any password based sign in.
- `otp` - any one-time password based sign in (email code, SMS code, magic
  link).
- `totp` - a TOTP additional factor.
- `sso/saml` - any Single Sign On (SAML) method.
- `anonymous` - any anonymous sign in.

The following additional claims are available when using PKCE flow:

- `invite` - any sign in via an invitation.
- `magiclink` - any sign in via magic link. Excludes logins resulting from invocation of `signUp`.
- `email/signup` - any login resulting from an email signup.
- `email_change` - any login resulting from a change in email.

More authentication methods will be added over time as we increase the number of authentication methods supported by Supabase.

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