Difference between revisions of "Legacy Mojang Authentication"

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Minecraft 1.6 introduced a new authentication scheme called Yggdrasil which completely replaces the [[Legacy_Authentication|previous authentication system]].
+
With the release of Minecraft 1.6, Mojang introduced a new authentication system called '''Yggdrasil''', which replaced the previous [[Legacy Authentication|Legacy authentication system]]. This authentication system is also used in Mojang's other game, Scrolls. According to Mojang, the Yggdrasil authentication system should be adopted by developers for custom login implementation, but they strongly advise against collecting credentials from users. For those utilizing newer Microsoft accounts, there is an alternative authentication scheme available called the [[Microsoft Authentication Scheme|Microsoft authentication scheme]].
  
== Request format ==
+
== Requests ==
 +
The Yggdrasil authentication system requests are made to the following server:
  
All requests to Yggdrasil are made to the following server:
+
https://authserver.mojang.com
  
  https://authserver.mojang.com
+
To ensure successful requests, they must adhere to the following guidelines:
 +
* Use a <code>POST</code> request method
 +
* Include a <code>Content-Type</code> header set to <code>application/json</code>
 +
* Contain a [[wikipedia:JSON|JSON]]-encoded dictionary as payload
  
Further, they are expected to fulfill the following rules:
+
In the event of a successful request, the server will return:
 +
* A <code>2XX</code> [[wikipedia:List of HTTP status codes|HTTP status code]] to indicate success
 +
* An empty payload or a [[wikipedia:JSON|JSON]]-encoded dictionary as specified in the API documentation
  
* Are <code>POST</code> requests
+
In the case of a failed request, the server will respond with:
* Have the <code>Content-Type</code> header set to <code>application/json</code>
+
* An [[wikipedia:List of HTTP status codes|HTTP status code]] other than <code>2XX</code> to indicate failure
* Contain a [http://json.org JSON]-encoded dictionary as payload
+
* A [[wikipedia:JSON|JSON]]-encoded dictionary following the format below:
 
 
If a request was successful the server will respond with:
 
 
 
* Status code <code>200</code>
 
* A [http://json.org JSON]-encoded dictionary according to the specifications below
 
 
 
If however a request fails, the server will respond with:
 
 
 
* An appropriate, non-200 [http://en.wikipedia.org/wiki/List_of_HTTP_status_codes HTTP status code]
 
* A [http://json.org JSON]-encoded dictionary following this format:
 
 
<syntaxhighlight lang="javascript">
 
<syntaxhighlight lang="javascript">
 
{
 
{
  "error": "Short description of the error",
+
    "error": "Short description of the error",
  "errorMessage": "Longer description which can be shown to the user",
+
    "cause": "Cause of the error" // optional
  "cause": "Cause of the error"        // optional
+
    "errorMessage": "Longer description which can be shown to the user",
 
}
 
}
 
</syntaxhighlight>
 
</syntaxhighlight>
  
 
== Errors ==
 
== Errors ==
These are some of the errors that can be encountered:
+
The following are examples of error scenarios that may occur during the use of the Yggdrasil authentication system:
 +
 
 
{| class="wikitable"
 
{| class="wikitable"
|-
+
|-
! Error
+
! STATUS
! Cause
+
! error
! Error message
+
! cause
! Notes
+
! errorMessage
|-
+
! NOTES
| <code>Method Not Allowed</code>
+
|-
|
+
| <code>415 Unsupported Media Type</code>
| The method specified in the request is not allowed for the resource identified by the request URI
+
| <code>Unsupported Media Type</code>
| Something other than a POST request was received.
+
|
|-
+
| The server is refusing to service the request because the entity of the request is in a format not supported by the requested resource for the requested method
| <code>Not Found</code>
+
| An attempt to send a POST request with incorrect request headers to any endpoint.
|
+
|-
| The server has not found anything matching the request URI
+
| <code>405 Method Not Allowed</code>
| Non-existing endpoint was called.
+
| <code>Method Not Allowed</code>
|-
+
|  
| <code>ForbiddenOperationException</code>
+
| The method specified in the request is not allowed for the resource identified by the request URI
| <code>UserMigratedException</code>
+
| An attempt to use a request method other than <code>POST</code> to access any of the endpoints.
| Invalid credentials. Account migrated, use e-mail as username.
+
|-
|  
+
| <code>404 Not Found</code>
|-
+
| <code>Not Found</code>
| <code>ForbiddenOperationException</code>
+
|
|  
+
| The server has not found anything matching the request URI
| Invalid credentials. Invalid username or password.
+
| An attempt to send a request to a non-existent endpoint.
|  
+
|-
|-
+
| <code>410 Gone</code>
| <code>ForbiddenOperationException</code>
+
| <code>GoneException</code>
|  
+
|
| Invalid token.
+
| Migrated
| <code>accessToken</code> was invalid.
+
| A successful attempt to sign in using a migrated Mojang account.
|-
+
|-
| <code>IllegalArgumentException</code>
+
| <code>403 Forbidden</code>
|  
+
| <code>ForbiddenOperationException</code>
| Access token already has a profile assigned.
+
|
| Selecting profiles isn't implemented yet.
+
| Forbidden
|}
+
| An attempt to sign in using empty or insufficiently short credentials.
 
+
|-
== Session ID ==
+
| <code>403 Forbidden</code>
 
+
| <code>ForbiddenOperationException</code>
Whenever a Mojang service requires a session ID, you can simply combine a valid <code>accessToken</code> with the corresponding profile identifier as follows:
+
|  
 
+
| Invalid credentials. Invalid username or password.
  token:<accessToken>:<profile ID>
+
| Either a successful attempt to sign in using an account with excessive login attempts or an unsuccessful attempt to sign in using a non-existent account.
 +
|-
 +
| <code>403 Forbidden</code>
 +
| <code>ForbiddenOperationException</code>
 +
|  
 +
| Invalid credentials. Legacy account is non-premium account.
 +
| An unsuccessful attempt to sign in using a Legacy account without a valid Minecraft purchase.
 +
|-
 +
| <code>403 Forbidden</code>
 +
| <code>ForbiddenOperationException</code>
 +
| <code>UserMigratedException</code>
 +
| Invalid credentials. Account migrated, use email as username.
 +
| An unsuccessful attempt to sign in using a migrated Legacy account.
 +
|-
 +
| <code>403 Forbidden</code>
 +
| <code>TooManyRequestsException</code>
 +
|
 +
| Token does not exist
 +
| An attempt to refresh an access token that has been invalidated, no longer exists, or has been erased.
 +
|-
 +
| <code>403 Forbidden</code>
 +
| <code>ForbiddenOperationException</code>
 +
|  
 +
| Invalid token
 +
| An attempt to validate an access token obtained from the <code>/authenticate</code> endpoint that has expired or become invalid.
 +
|-
 +
| <code>429 Too Many Requests</code>
 +
| <code>ForbiddenOperationException</code>
 +
|
 +
| Invalid token.
 +
| An attempt to validate an access token obtained from the <code>/authenticate</code> endpoint that has expired or become invalid while under rate-limiting conditions.
 +
|}
  
 
== Authenticate ==
 
== Authenticate ==
  
Authenticates a user using his password.
+
Authenticates a user using their password.
  
 
=== Endpoint ===
 
=== Endpoint ===
  /authenticate
+
 
 +
/authenticate
  
 
=== Payload ===
 
=== Payload ===
 +
 
<syntaxhighlight lang="javascript">
 
<syntaxhighlight lang="javascript">
 
{
 
{
  "agent": {                             // optional
+
    "agent": {                             // defaults to Minecraft
    "name": "Minecraft",                 // So far this is the only encountered value
+
        "name": "Minecraft",               // For Mojang's other game Scrolls, "Scrolls" should be used
    "version": 1                         // This number might be increased
+
        "version": 1                       // This number might be increased
                                        // by the vanilla client in the future
+
                                            // by the vanilla client in the future
  },
+
    },
  "username": "mojang account name",     // Can be an email address or player name for
+
    "username": "mojang account name",     // Can be an email address or player name for
                                        // unmigrated accounts
+
                                            // unmigrated accounts
  "password": "mojang account password",
+
    "password": "mojang account password",
  "clientToken": "client identifier"    // optional
+
    "clientToken": "client identifier",     // optional
 +
    "requestUser": true                    // optional; default: false; true adds the user object to the response
 
}
 
}
 
</syntaxhighlight>
 
</syntaxhighlight>
  
The <code>clientToken</code> should be a randomly generated identifier and must be identical for each request.
+
The <code>clientToken</code> should be a randomly generated identifier and must be identical for each request. The vanilla launcher generates a random (version 4) UUID on first run and saves it, reusing it for every subsequent request. In case it is omitted the server will generate a random token based on Java's [http://docs.oracle.com/javase/7/docs/api/java/util/UUID.html#toString() <code>UUID.toString()</code>] which should then be stored by the client. This will however also invalidate all previously acquired <code>accessToken</code>s for this user across all clients.
In case it is omitted the server will generate a random token based on Java's [http://docs.oracle.com/javase/7/docs/api/java/util/UUID.html#toString() UUID.toString()] which should then be stored by the client. This will however also invalidate all previously acquired <code>accessToken</code>s for this user across all clients.
 
  
 
=== Response ===
 
=== Response ===
 +
 
<syntaxhighlight lang="javascript">
 
<syntaxhighlight lang="javascript">
 
{
 
{
  "accessToken": "random access token", // hexadecimal
+
    "user": {
  "clientToken": "client identifier",   // identical to the one received
+
        "username": "user@email.example", // will be account username for legacy accounts
  "availableProfiles": [                 // only present if the agent field was received
+
        "properties": [
     {
+
            {
      "id": "profile identifier",       // hexadecimal
+
                "name": "preferredLanguage",
      "name": "player name"
+
                "value": "en-us"
 +
            },
 +
            {
 +
                "name": "registrationCountry",
 +
                "value": "country" // 2L country (e.g. US)
 +
            }
 +
        ],
 +
        "id": "hexadecimal string" // This is the remoteID for the user
 +
    },
 +
    "clientToken": "client identifier",
 +
    "accessToken": "random access token", // hexadecimal or JSON-Web-Token (unconfirmed) [The normal accessToken can be found in the payload of the JWT (second by '.' separated part as Base64 encoded JSON object), in key "yggt"]
 +
    "availableProfiles": [
 +
        {
 +
            "name": "player username",
 +
            "id": "hexadecimal string" // UUID of the account
 +
        }
 +
    ],
 +
     "selectedProfile": {
 +
        "name": "player username",
 +
        "id": "hexadecimal string" // UUID of the account
 
     }
 
     }
  ],
 
  "selectedProfile": {                  // only present if the agent field was received
 
    "id": "profile identifier",
 
    "name": "player name"
 
  }
 
 
}
 
}
 
</syntaxhighlight>
 
</syntaxhighlight>
'''Note:''' If a user wishes to stay logged in on his computer you are strongly advised to store the received <code>accessToken</code> instead of the password itself.
 
  
Currently each account will only have one single profile, multiple profiles per account are however planned in the future.
+
'''Note:''' If a user wishes to stay logged in on their computer you are strongly advised to store the received <code>accessToken</code> instead of the password itself.
 +
 
 +
Currently each account will only have one single profile, multiple profiles per account are however planned in the future. If a user attempts to log into a valid Mojang account with no attached Minecraft license, the authentication will be successful, but the response will not contain a <code>selectedProfile</code> field, and the <code>availableProfiles</code> array will be empty.
 +
 
 +
Some instances in the wild have been observed of Mojang returning a flat <code>null</code> for failed refresh attempts against legacy accounts. It's not clear what the actual error tied to the null response is and it is extremely rare, but implementations should be wary of null output from the response.
 +
 
 +
This endpoint is severely rate-limited: multiple <code>/authenticate</code> requests for the same account in a short amount of time (think 3 requests in a few seconds), even with the correct password, will eventually lead to an <code>Invalid credentials.</code> response. This error clears up a few seconds later.
  
 
== Refresh ==
 
== Refresh ==
  
Refreshes a valid <code>accessToken</code>. It can be uses to keep a user logged in between gaming sessions and is preferred over storing the user's password in a file (see [[lastlogin]]).  
+
Refreshes a valid <code>accessToken</code>. It can be used to keep a user logged in between gaming sessions and is preferred over storing the user's password in a file (see [[lastlogin]]).  
  
 
=== Endpoint ===
 
=== Endpoint ===
  /refresh
+
 
 +
/refresh
  
 
=== Payload ===
 
=== Payload ===
 
<syntaxhighlight lang="javascript">
 
<syntaxhighlight lang="javascript">
 
{
 
{
  "accessToken": "valid accessToken",
+
    "accessToken": "valid accessToken",
  "clientToken": "client identifier"     // This needs to be identical to the one used
+
    "clientToken": "client identifier"// This needs to be identical to the one used
 
                                         // to obtain the accessToken in the first place
 
                                         // to obtain the accessToken in the first place
  "selectedProfile": {                   // optional; sending it will result in an error
+
    "selectedProfile": {                 // optional; sending it will result in an error
    "id": "profile identifier",         // hexadecimal
+
        "id": "profile identifier",     // hexadecimal
    "name": "player name"
+
        "name": "player name"
  }
+
    },
 +
    "requestUser": true                  // optional; default: false; true adds the user object to the response
 
}
 
}
 
</syntaxhighlight>
 
</syntaxhighlight>
Line 145: Line 197:
  
 
=== Response ===
 
=== Response ===
 +
 
<syntaxhighlight lang="javascript">
 
<syntaxhighlight lang="javascript">
 
{
 
{
  "accessToken": "random access token", // hexadecimal
+
    "accessToken": "random access token",     // hexadecimal
  "clientToken": "client identifier",   // identical to the one received
+
    "clientToken": "client identifier",       // identical to the one received
  "selectedProfile": {
+
    "selectedProfile": {
    "id": "profile identifier",         // hexadecimal
+
        "id": "profile identifier",           // hexadecimal
    "name": "player name"
+
        "name": "player name"
   }
+
    },
 +
    "user": {                                  // only present if requestUser was true in the request payload
 +
        "username": "user@email.example",      // email for Mojang accounts or account username for legacy Minecraft accounts
 +
        "id": "user identifier",              // hexadecimal
 +
        "properties": [
 +
            {
 +
                "name": "preferredLanguage",   // might not be present for all accounts
 +
                "value": "en"                  // Java locale format (https://docs.oracle.com/javase/8/docs/api/java/util/Locale.html#toString--)
 +
            },
 +
            {
 +
                "name": "twitch_access_token", // only present if a twitch account is associated (see https://account.mojang.com/me/settings)
 +
                "value": "twitch oauth token"  // OAuth 2.0 Token; alphanumerical; e.g. https://api.twitch.tv/kraken?oauth_token=[...]
 +
                                              // the Twitch API is documented here: https://github.com/justintv/Twitch-API
 +
            }
 +
        ]
 +
    }
 
}
 
}
 
</syntaxhighlight>
 
</syntaxhighlight>
Line 158: Line 226:
 
== Validate ==
 
== Validate ==
  
Checks if an <code>accessToken</code> is valid.
+
Checks if an <code>accessToken</code> is usable for authentication with a Minecraft server. The Minecraft Launcher (as of version 1.6.13) calls this endpoint on startup to verify that its saved token is still usable, and calls <code>/refresh</code> if this returns an error.
 +
 
 +
Note that an <code>accessToken</code> may be unusable for authentication with a Minecraft server, but still be good enough for <code>/refresh</code>. This mainly happens when one has used another client (e.g. played Minecraft on another PC with the same account). It seems only the most recently obtained <code>accessToken</code> for a given account can reliably be used for authentication (the next-to-last token also seems to remain valid, but don't rely on it).
 +
 
 +
<code>/validate</code> may be called with or without a <code>clientToken</code>. If a <code>clientToken</code> is provided, it should match the one used to obtain the <code>accessToken</code>. The Minecraft Launcher does send a <code>clientToken</code> to <code>/validate</code>.
  
 
=== Endpoint ===
 
=== Endpoint ===
  /validate
+
 
 +
/validate
  
 
=== Payload ===
 
=== Payload ===
 +
 
<syntaxhighlight lang="javascript">
 
<syntaxhighlight lang="javascript">
 
{
 
{
  "accessToken": "valid accessToken",
+
    "accessToken": "valid accessToken",
 +
    "clientToken": "associated clientToken" // optional, see above
 
}
 
}
 
</syntaxhighlight>
 
</syntaxhighlight>
  
 
=== Response ===
 
=== Response ===
Unlike most other methods this one will return an empty payload if successful.
+
 
 +
Returns an empty payload (<code>204 No Content</code>) if successful, an error JSON with status <code>403 Forbidden</code> otherwise.
 +
 
 +
== Signout ==
 +
 
 +
Invalidates <code>accessToken</code>s using an account's username and password.
 +
 
 +
=== Endpoint ===
 +
 
 +
/signout
 +
 
 +
=== Payload ===
 +
 
 +
<syntaxhighlight lang="javascript">
 +
{
 +
    "username": "mojang account name",
 +
    "password": "mojang account password"
 +
}
 +
</syntaxhighlight>
 +
 
 +
=== Response ===
 +
 
 +
Returns an empty payload if successful.
 +
 
 +
== Invalidate ==
 +
 
 +
Invalidates <code>accessToken</code>s using a client/access token pair.
 +
 
 +
=== Endpoint ===
 +
 
 +
/invalidate
 +
 
 +
=== Payload ===
 +
 
 +
<syntaxhighlight lang="javascript">
 +
{
 +
    "accessToken": "valid accessToken",
 +
    "clientToken": "client identifier"  // This needs to be identical to the one used
 +
                                        // to obtain the accessToken in the first place
 +
}
 +
</syntaxhighlight>
 +
 
 +
=== Response ===
 +
 
 +
Returns an empty payload if successful.
  
 
== Joining a Server ==
 
== Joining a Server ==
  
See [[Protocol Encryption#Authentication|Protocol Encryption]]
+
See [[Protocol Encryption#Authentication]]
 +
 
 +
== Examples ==
 +
 
 +
[https://github.com/iBuyMountainDew/yggdrasil Kotlin] | Full Yggdrasil wrapper in Kotlin.
  
 +
[https://github.com/Kronos666/mclaunch-util-lib Java] | Legacy full Yggdrasil wrapper in Java.
  
[[Category:Protocol Details]]
 
 
[[Category:Minecraft Modern]]
 
[[Category:Minecraft Modern]]

Latest revision as of 18:56, 26 February 2024

With the release of Minecraft 1.6, Mojang introduced a new authentication system called Yggdrasil, which replaced the previous Legacy authentication system. This authentication system is also used in Mojang's other game, Scrolls. According to Mojang, the Yggdrasil authentication system should be adopted by developers for custom login implementation, but they strongly advise against collecting credentials from users. For those utilizing newer Microsoft accounts, there is an alternative authentication scheme available called the Microsoft authentication scheme.

Requests

The Yggdrasil authentication system requests are made to the following server:

https://authserver.mojang.com

To ensure successful requests, they must adhere to the following guidelines:

  • Use a POST request method
  • Include a Content-Type header set to application/json
  • Contain a JSON-encoded dictionary as payload

In the event of a successful request, the server will return:

  • A 2XX HTTP status code to indicate success
  • An empty payload or a JSON-encoded dictionary as specified in the API documentation

In the case of a failed request, the server will respond with:

  • An HTTP status code other than 2XX to indicate failure
  • A JSON-encoded dictionary following the format below:
{
    "error": "Short description of the error",
    "cause": "Cause of the error" // optional
    "errorMessage": "Longer description which can be shown to the user",
}

Errors

The following are examples of error scenarios that may occur during the use of the Yggdrasil authentication system:

STATUS error cause errorMessage NOTES
415 Unsupported Media Type Unsupported Media Type The server is refusing to service the request because the entity of the request is in a format not supported by the requested resource for the requested method An attempt to send a POST request with incorrect request headers to any endpoint.
405 Method Not Allowed Method Not Allowed The method specified in the request is not allowed for the resource identified by the request URI An attempt to use a request method other than POST to access any of the endpoints.
404 Not Found Not Found The server has not found anything matching the request URI An attempt to send a request to a non-existent endpoint.
410 Gone GoneException Migrated A successful attempt to sign in using a migrated Mojang account.
403 Forbidden ForbiddenOperationException Forbidden An attempt to sign in using empty or insufficiently short credentials.
403 Forbidden ForbiddenOperationException Invalid credentials. Invalid username or password. Either a successful attempt to sign in using an account with excessive login attempts or an unsuccessful attempt to sign in using a non-existent account.
403 Forbidden ForbiddenOperationException Invalid credentials. Legacy account is non-premium account. An unsuccessful attempt to sign in using a Legacy account without a valid Minecraft purchase.
403 Forbidden ForbiddenOperationException UserMigratedException Invalid credentials. Account migrated, use email as username. An unsuccessful attempt to sign in using a migrated Legacy account.
403 Forbidden TooManyRequestsException Token does not exist An attempt to refresh an access token that has been invalidated, no longer exists, or has been erased.
403 Forbidden ForbiddenOperationException Invalid token An attempt to validate an access token obtained from the /authenticate endpoint that has expired or become invalid.
429 Too Many Requests ForbiddenOperationException Invalid token. An attempt to validate an access token obtained from the /authenticate endpoint that has expired or become invalid while under rate-limiting conditions.

Authenticate

Authenticates a user using their password.

Endpoint

/authenticate

Payload

{
    "agent": {                              // defaults to Minecraft
        "name": "Minecraft",                // For Mojang's other game Scrolls, "Scrolls" should be used
        "version": 1                        // This number might be increased
                                            // by the vanilla client in the future
    },
    "username": "mojang account name",      // Can be an email address or player name for
                                            // unmigrated accounts
    "password": "mojang account password",
    "clientToken": "client identifier",     // optional
    "requestUser": true                     // optional; default: false; true adds the user object to the response
}

The clientToken should be a randomly generated identifier and must be identical for each request. The vanilla launcher generates a random (version 4) UUID on first run and saves it, reusing it for every subsequent request. In case it is omitted the server will generate a random token based on Java's UUID.toString() which should then be stored by the client. This will however also invalidate all previously acquired accessTokens for this user across all clients.

Response

{
    "user": {
        "username": "user@email.example", // will be account username for legacy accounts
        "properties": [
            {
                "name": "preferredLanguage",
                "value": "en-us"
            },
            {
                "name": "registrationCountry",
                "value": "country" // 2L country (e.g. US)
            }
        ],
        "id": "hexadecimal string" // This is the remoteID for the user
    },
    "clientToken": "client identifier",
    "accessToken": "random access token", // hexadecimal or JSON-Web-Token (unconfirmed) [The normal accessToken can be found in the payload of the JWT (second by '.' separated part as Base64 encoded JSON object), in key "yggt"]
    "availableProfiles": [
        {
            "name": "player username",
            "id": "hexadecimal string" // UUID of the account
        }
    ],
    "selectedProfile": {
        "name": "player username",
        "id": "hexadecimal string" // UUID of the account
    }
}

Note: If a user wishes to stay logged in on their computer you are strongly advised to store the received accessToken instead of the password itself.

Currently each account will only have one single profile, multiple profiles per account are however planned in the future. If a user attempts to log into a valid Mojang account with no attached Minecraft license, the authentication will be successful, but the response will not contain a selectedProfile field, and the availableProfiles array will be empty.

Some instances in the wild have been observed of Mojang returning a flat null for failed refresh attempts against legacy accounts. It's not clear what the actual error tied to the null response is and it is extremely rare, but implementations should be wary of null output from the response.

This endpoint is severely rate-limited: multiple /authenticate requests for the same account in a short amount of time (think 3 requests in a few seconds), even with the correct password, will eventually lead to an Invalid credentials. response. This error clears up a few seconds later.

Refresh

Refreshes a valid accessToken. It can be used to keep a user logged in between gaming sessions and is preferred over storing the user's password in a file (see lastlogin).

Endpoint

/refresh

Payload

{
    "accessToken": "valid accessToken",
    "clientToken": "client identifier",  // This needs to be identical to the one used
                                         // to obtain the accessToken in the first place
    "selectedProfile": {                 // optional; sending it will result in an error
        "id": "profile identifier",      // hexadecimal
        "name": "player name"
    },
    "requestUser": true                  // optional; default: false; true adds the user object to the response
}

Note: The provided accessToken gets invalidated.

Response

{
    "accessToken": "random access token",      // hexadecimal
    "clientToken": "client identifier",        // identical to the one received
    "selectedProfile": {
        "id": "profile identifier",            // hexadecimal
        "name": "player name"
    },
    "user": {                                  // only present if requestUser was true in the request payload
        "username": "user@email.example",      // email for Mojang accounts or account username for legacy Minecraft accounts
        "id": "user identifier",               // hexadecimal
        "properties": [
            {
                "name": "preferredLanguage",   // might not be present for all accounts
                "value": "en"                  // Java locale format (https://docs.oracle.com/javase/8/docs/api/java/util/Locale.html#toString--)
            },
            {
                "name": "twitch_access_token", // only present if a twitch account is associated (see https://account.mojang.com/me/settings)
                "value": "twitch oauth token"  // OAuth 2.0 Token; alphanumerical; e.g. https://api.twitch.tv/kraken?oauth_token=[...]
                                               // the Twitch API is documented here: https://github.com/justintv/Twitch-API
            }
        ]
    }
}

Validate

Checks if an accessToken is usable for authentication with a Minecraft server. The Minecraft Launcher (as of version 1.6.13) calls this endpoint on startup to verify that its saved token is still usable, and calls /refresh if this returns an error.

Note that an accessToken may be unusable for authentication with a Minecraft server, but still be good enough for /refresh. This mainly happens when one has used another client (e.g. played Minecraft on another PC with the same account). It seems only the most recently obtained accessToken for a given account can reliably be used for authentication (the next-to-last token also seems to remain valid, but don't rely on it).

/validate may be called with or without a clientToken. If a clientToken is provided, it should match the one used to obtain the accessToken. The Minecraft Launcher does send a clientToken to /validate.

Endpoint

/validate

Payload

{
    "accessToken": "valid accessToken",
    "clientToken": "associated clientToken" // optional, see above
}

Response

Returns an empty payload (204 No Content) if successful, an error JSON with status 403 Forbidden otherwise.

Signout

Invalidates accessTokens using an account's username and password.

Endpoint

/signout

Payload

{
    "username": "mojang account name",
    "password": "mojang account password"
}

Response

Returns an empty payload if successful.

Invalidate

Invalidates accessTokens using a client/access token pair.

Endpoint

/invalidate

Payload

{
    "accessToken": "valid accessToken",
    "clientToken": "client identifier"   // This needs to be identical to the one used
                                         // to obtain the accessToken in the first place
}

Response

Returns an empty payload if successful.

Joining a Server

See Protocol Encryption#Authentication

Examples

Kotlin | Full Yggdrasil wrapper in Kotlin.

Java | Legacy full Yggdrasil wrapper in Java.