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About usernames with external authentication

If you use an enterprise with Enterprise Managed Users, members of your enterprise authenticate to access GitHub through your SAML identity provider (IdP). For more information, see "About Enterprise Managed Users" and "About identity and access management."

GitHub automatically creates a username for each person when their user account is provisioned via SCIM.

• To create the username, GitHub normalizes an identifier provided by your IdP.
• On GitHub.com, GitHub also adds an underscore and your enterprise's shortcode to the end of each username.

If multiple identifiers are normalized into the same username, a username conflict occurs, and only the first user account is created. You can resolve username problems by making a change in your IdP so that the normalized usernames will be unique and within the 39-character limit.

About shortcodes for managed user accounts

Each enterprise that uses managed user accounts is associated with a shortcode, which is an alphanumeric string between three and eight characters.

Shortcodes on GitHub.com

When you create an enterprise with managed users on GitHub.com, you choose a shortcode that will be used as the suffix for all your enterprise members' usernames.

• The short code must be unique to your enterprise and contain no special characters.
• Choose carefully, because it is not possible to modify the shortcode after your enterprise with managed users has been created.

The setup user who configures SAML SSO has a username in the format of SHORT-CODE_admin. For example, if your enterprise's shortcode is "octo", the setup user will be "octo_admin."

When you provision a new user from your identity provider, the new managed user account will have a GitHub username in the format of @IDP-USERNAME_SHORT-CODE (for example, "mona-cat_octo").

Shortcodes on GHE.com

If you use GitHub Enterprise Cloud with data residency, when you create an enterprise with managed users on GHE.com, your enterprise's shortcode is randomly generated.

• The shortcode is not used as a suffix in the usernames of provisioned users.
• The only place you are likely to see the shortcode is in the username of the setup admin, which will look like 2abvd19d_admin.

About normalized usernames

Usernames are formed by normalizing the SCIM userName attribute value sent from the IdP.

Identity provider	GitHub username
Microsoft Entra ID (previously known as Azure AD)	IDP-USERNAME is formed by normalizing the characters preceding the @ character in the UPN (User Principal Name), which does not include the #EXT# for guest accounts.
Okta	IDP-USERNAME is the normalized username attribute provided by the IdP.

These rules may result in your IdP providing the same IDP-USERNAME for multiple users. For example, for Entra ID, the following UPNs will result in the same username:

• bob@contoso.com
• bob@fabrikam.com
• bob#EXT#fabrikamcom@contoso.com
• bob_example#EXT#fabrikamcom@contoso.com
• bob_example.com#EXT#fabrikamcom@contoso.com

This will cause a username conflict, and only the first user will be provisioned. For more information, see "Resolving username problems."

Usernames, including underscore and short code, must not exceed 39 characters.

About username normalization

Usernames for user accounts on GitHub can only contain alphanumeric characters and dashes (-).

When you configure SAML authentication, GitHub Enterprise Cloud uses the SCIM userName attribute value sent from the IdP to determine the username for the corresponding user account on GitHub. If this value includes unsupported characters, GitHub Enterprise Cloud will normalize the username per the following rules.

1. GitHub Enterprise Cloud will normalize any non-alphanumeric character in your account's username into a dash. For example, a username of mona.the.octocat will be normalized to mona-the-octocat. Note that normalized usernames also can't start or end with a dash. They also can't contain two consecutive dashes.

2. Usernames created from email addresses are created from the normalized characters that precede the @ character.

3. Usernames created from domain accounts are created from the normalized characters after the \\ separator.

4. If multiple accounts are normalized into the same GitHub Enterprise Cloud username, only the first user account is created. Subsequent users with the same username won't be able to sign in. For more information, see "Resolving username problems."

Examples of username normalization

Identifier on provider	Normalized username on GitHub.com	Result
The.Octocat	the-octocat_SHORT-CODE	This username is created successfully.
!The.Octocat	-the-octocat_SHORT-CODE	This username is not created, because it starts with a dash.
The.Octocat!	the-octocat-_SHORT-CODE	This username is not created, because it ends with a dash.
The!!Octocat	the--octocat_SHORT-CODE	This username is not created, because it contains two consecutive dashes.
The!Octocat	the-octocat_SHORT-CODE	This username is not created. Although the normalized username is valid, it already exists.
The.Octocat@example.com	the-octocat_SHORT-CODE	This username is not created. Although the normalized username is valid, it already exists.
internal\\The.Octocat	the-octocat_SHORT-CODE	This username is not created. Although the normalized username is valid, it already exists.
mona.lisa.the.octocat.from.github.united.states@example.com	mona-lisa-the-octocat-from-github-united-states_SHORT-CODE	This username is not created, because it exceeds the 39-character limit.

Resolving username problems

When a new user is being provisioned, if the username is longer than 39 characters (including underscore and short code), or conflicts with an existing user in the enterprise, the provisioning attempt will fail with a 409 error.

To resolve this problem, you must make one of the following changes in your IdP so that all normalized usernames will be within the character limit and unique.

• Change the userName attribute value for individual users that are causing problems
• Change the userName attribute mapping for all users
• Configure a custom userName attribute for all users

When you change the attribute mapping, usernames of existing managed user accounts will be updated, but nothing else about the accounts will change, including activity history.

Resolving username problems with Entra ID

To resolve username problems in Entra ID, either modify the User Principal Name value for the conflicting user or modify the attribute mapping for the userName attribute. If you modify the attribute mapping, you can choose an existing attribute or use an expression to ensure that all provisioned users have a unique normalized alias.

1. In Entra ID, open the GitHub Enterprise Managed User application.
2. In the left sidebar, click Provisioning.
3. Click Edit Provisioning.
4. Expand Mappings, then click Provision Entra ID Users.
5. Click the GitHub userName attribute mapping.
6. Change the attribute mapping.
   • To map an existing attribute in Entra ID to the userName attribute in GitHub, click your desired attribute field. Then, save and wait for a provisioning cycle to occur within about 40 minutes.
   • To use an expression instead of an existing attribute, change the Mapping type to "Expression", then add a custom expression that will make this value unique for all users. For example, you could use [FIRST NAME]-[LAST NAME]-[EMPLOYEE ID]. For more information, see Reference for writing expressions for attribute mappings in Microsoft Entra ID on Microsoft Learn.

Resolving username problems with Okta

To resolve username problems in Okta, update the attribute mapping settings for the GitHub Enterprise Managed User application.

1. In Okta, open the GitHub Enterprise Managed User application.
2. Click Sign On.
3. In the "Settings" section, click Edit.
4. Update the "Application username format."