Identity API v2.0 and v3 History


As of the Queens release, Keystone solely implements the Identity API v3. Support for Identity API v2.0 has been removed in Queens in favor of the Identity API v3.

Identity API v3 is a superset of all the functionality available in the Identity API v2.0 and several of its extensions, and provides a much more consistent developer experience.


You’re probably wondering why Keystone does not implement a “v1” API. As a matter of fact, one exists, but it actually predates OpenStack. The v1.x API was an extremely small API documented and implemented by Rackspace for their early public cloud products.

With the advent of OpenStack, Keystone served to provide a superset of the authentication and multi-tenant authorization models already implemented by Rackspace’s public cloud, Nova, and Swift. Thus, Identity API v2.0 was introduced.

Identity API v3 was established to introduce namespacing for users and projects by using “domains” as a higher-level container for more flexible identity management and fixed a security issue in the v2.0 API (bearer tokens appearing in URLs).

How do I migrate from v2.0 to v3?

I am a deployer

You need to ensure that you’ve configured your service catalog in Keystone correctly. The simplest, and most ideal, configuration would expose one identity with unversioned endpoints (note the lack of /v2.0/ or /v3/ in these URLs):

  • Service (type: identity)

    • Endpoint (interface: public, URL: http://identity:5000/)

    • Endpoint (interface: admin, URL: http://identity:35357/)

If you were to perform a GET against either of these endpoints, you would be greeted by an HTTP/1.1 300 Multiple Choices response, which newer Keystone clients can use to automatically detect available API versions.


Deploying v3 only requires a single application since administrator and end-user operations are handled by the same process, and not separated into two different applications. Depending on how v2.0 was configured, you might be able to decommission one endpoint. Until users are educated about which endpoint to use, the former admin API (e.g. using port 35357) and the public API (e.g. using port 5000) can run the v3 API simulateously and serve both sets of users.

$ curl -i http://identity:35357/
HTTP/1.1 300 Multiple Choices
Vary: X-Auth-Token
Content-Type: application/json
Content-Length: 755
Date: Tue, 10 Jun 2014 14:22:26 GMT

{"versions": {"values": [ ... ]}}

With unversioned identity endpoints in the service catalog, you should be able to authenticate with keystoneclient successfully.

I have a Python client

The Keystone community provides first-class support for Python API consumers via our client library, python-keystoneclient. If you’re not currently using this library, you should, as it is intended to expose all of our HTTP API functionality. If we’re missing something you’re looking for, please contribute!

Adopting python-keystoneclient should be the easiest way to migrate to Identity API v3.

I have a non-Python client

You’ll likely need to heavily reference our API documentation to port your application to Identity API v3.

The most common operation would be password-based authentication including a tenant name (i.e. project name) to specify an authorization scope. In Identity API v2.0, this would be a request to POST /v2.0/tokens:

    "auth": {
        "passwordCredentials": {
            "password": "my-password",
            "username": "my-username"
        "tenantName": "project-x"

And you would get back a JSON blob with an access -> token -> id that you could pass to another web service as your X-Auth-Token header value.

In Identity API v3, an equivalent request would be to POST /v3/auth/tokens:

    "auth": {
        "identity": {
            "methods": [
            "password": {
                "user": {
                    "domain": {
                        "id": "default"
                    "name": "my-username",
                    "password": "my-password"
        "scope": {
            "project": {
                "domain": {
                    "id": "default"
                "name": "project-x"

Note a few key differences when compared to the v2.0 API:

  • A “tenant” in v2.0 became a “project” in v3.

  • The authentication method (password) is explicitly identified.

  • Both the user name (my-username) and project name (project-x) are namespaced by an owning domain (where id = default). The “default” domain exists by default in Keystone, and automatically owns the namespace exposed by Identity API v2.0. Alternatively, you may reference users and projects that exist outside the namespace of the default domain, which are thus inaccessible to the v2.0 API.

  • In v3, your token is returned to you in an X-Subject-Token header, instead of as part of the request body. You should still authenticate yourself to other services using the X-Auth-Token header.

Why do I see deployments with Keystone running on two ports?

During development of the v2.0 API, operational functionality was isolated into different applications within the project. One application was dedicated to end-user functionality and its sole purpose was to authenticate and validate user identities. The second application consisted of more features and allowed operators the ability to manage their deployment by adding or deleting users, creating projects, etc. These applications were referred to as the public and admin APIs, respectively. This deployment model was required by the architecture of the v2.0 API. In a way, authorization was limited to the application you had access to.

Once development began on the v3 API, the code paths for both applications were merged into one. Instead of isolating functionality into separate applications, all functionality was consolidated into a single application. Each v3 endpoint or API is protected by policy instead. This makes deployment and management of Keystone’s infrastructure easier for operators to deploy and for users to consume. As a result, Keystone deployments are not required to deploy separate admin and public endpoints, especially now that the v2.0 API implementation has been removed.

HTTP/1.1 Chunked Encoding


Running Keystone under HTTPD in the recommended (and tested) configuration does not support the use of Transfer-Encoding: chunked. This is due to a limitation with the WSGI spec and the implementation used by mod_wsgi. It is recommended that all clients assume Keystone will not support Transfer-Encoding: chunked.