> For the complete documentation index, see [llms.txt](https://dev.ishare.eu/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://dev.ishare.eu/version-3.0/introduction/specific-technical-standards/oauth-2.0.md).

# OAuth 2.0

iSHARE uses the OAuth 2.0 protocol for authenticating parties and providing access tokens when requesting access to a service within iSHARE (for machine-to-machine (M2M) communication). Specifically, it uses the OAuth 2.0 Client Credentials flow.

On this page, a brief description of OAuth is provided. For the most recent version of the OAuth 2.0 specification, click on [this link](https://oauth.net/2/).

iSHARE facilitates an ecosystem within which parties can interact with previously unknown parties; pre-registration is therefore not a prerequisite and thus requires alterations to the official standard.

### iSHARE authentication flow <a href="#oauth2.0-ishareauthenticationflow" id="oauth2.0-ishareauthenticationflow"></a>

iSHARE requirements for iSHARE M2M OAuth 2.0-based Authentication are defined [here](/version-3.0/reference/authentication.md#machine-to-machine-m2m-authentication).

### OAuth 2.0 general description <a href="#oauth2.0-oauth2.0generaldescription" id="oauth2.0-oauth2.0generaldescription"></a>

OAuth is an open standard for authorisation, which is used by e.g. Google, Facebook, Microsoft, Twitter, etc. to let their users exchange information about their accounts with other applications or websites. OAuth is designed to work with HTTP.

Through OAuth, users can authorise third-party applications or websites to access their account information on other "master" systems without the need to exchange their credentials to log in to the platform. OAuth provides a "secure delegated access" to resources (email accounts, picture accounts, etc.) on behalf of the resource owner.

It specifies a method for resource owners to authorise third-party access to their resources without exchanging their credentials (username, password). Authorisation servers (of the platform) issue access tokens to third-party clients (applications or websites) with the approval of the resource owner (= end user). The third-party client needs the access token to get access to the resources that are stored on the resource server (of the master system).


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