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OAuth Grant Types Explained in Detailed

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OAuth Grant Types Explained in Detailed

OAuth, the backbone of secure data sharing, operates via "grant types" – routes permitting third-party app access to user resources. This article provides crisp insights into these grant types using real-world examples.

OAuth, the backbone of secure data sharing, operates via "grant types" – routes permitting third-party app access to user resources. This article provides crisp insights into these grant types in OAuth using real-world examples. Whether you're new to OAuth or an expert, discover how these grant types bolster digital security in various application scenarios.

OAuth Grant Types Explained

OAuth is an open standard for access delegation that allows users to grant third-party applications access to their data on other services, without exposing their credentials. Instead of usernames and passwords, OAuth uses tokens to authorize access.

OAuth defines several grant types for different use cases. The grant type determines how the token is issued and the level of access it provides. Understanding OAuth grant types is important for implementing secure authorization flows in your applications. In this post, we'll explain the 4 main OAuth grant types with examples of how they work.

What Are Grant Types in OAuth

OAuth grant types are predefined authorization mechanisms that define how a client application can obtain access tokens from a resource owner (user) and utilize them to access protected resources on their behalf. These grant types cater to different scenarios and security requirements, ensuring that applications can securely access user data without exposing sensitive credentials.

There are several common OAuth grant types, each tailored to specific use cases:

Authorization Code Grant

The authorization code grant is commonly used by web applications executing on a server. Some examples:

  • A web app that allows users to sign in with their Google account and access their Gmail and Google Drive using Google's APIs.
  • A website that uses Facebook Login to authenticate users and then calls Facebook's Graph API to access their profile information.
  • A blog site that allows commenting with a Twitter account and uses the authorization code grant to get access tokens to call the Twitter API.

Implicit Grant

The implicit grant is most useful for browser-based apps and mobile apps where the client's secret confidentiality requirements are not met. Some examples:

  • A JavaScript single-page app that reads and writes user's data from an API. The user signs in with OAuth and the app uses the implicit grant to retrieve access tokens.
  • A native mobile app that authenticates users via OAuth and then calls an API to display their data. The implicit grant enables getting the token on mobile.
  • A distributed JavaScript app that calls multiple APIs from the browser. The implicit grant allows getting a token from each API.

Resource Owner Password Credentials Grant

The resource owner password credentials grant is suitable when the client is highly trusted and can collect user credentials directly. Some examples:

  • A legacy app migrating to OAuth, where users previously directly input their usernames and passwords into the app to authenticate and access data.
  • Apps that have highly trusted relationships with the users where inputting their credentials is appropriate, such as enterprise or SMB tools.
  • IoT devices where users log into the device itself which then needs to call APIs on the user's behalf.

Client Credentials Grant

The client credentials grant enables machine-to-machine authentication for non-user-based app APIs. Some examples:

  • Server-to-server access where a cron job needs to call an API without user context.
  • Syncing data overnight between two separate systems where no user is logged in.
  • Infrastructure monitoring daemons that check APIs to gather metrics and status.
  • Automated build systems calling a remote API as part of the development pipeline.

OAuth Grant Types Use Cases

Apidog, a versatile API testing and development tool, has revolutionized the way developers interact with APIs. In the context of OAuth grant types, Apidog plays a pivotal role in simplifying the testing and implementation of secure authorization flows.


OAuth, with its various grant types like Authorization Code, Implicit, Resource Owner Password Credentials, and Client Credentials, ensures secure access to APIs. However, testing these flows manually can be intricate and time-consuming. This is where Apidog comes to the rescue. For more gateway authentication information about Apidog,  please check below:

API Gateway Authentication (Apidog Tutorial)
API Gateway Authentication refers to the process of verifying the identity of users or applications that are trying to access an API through an API gateway.

Apidog's Features for OAuth Grant Types:

  1. User-Friendly Interface: Apidog provides an intuitive interface that simplifies the configuration of OAuth settings. Developers can easily set up authorization URLs, scopes, and other parameters required for different grant types.
  2. Authorization Helpers: Apidog offers built-in authorization helpers that streamline the process of obtaining access tokens. With just a few clicks, developers can initiate authorization flows, complete with redirect URLs and user consent.
  3. Dynamic Token Management: Apidog's environment variables enable dynamic token management. Access tokens obtained during the authorization process can be stored and reused throughout API testing, mirroring real-world scenarios.
  4. Pre-Built OAuth Templates: Apidog offers pre-built OAuth templates for common providers like Google and GitHub. These templates eliminate the need for manual setup and allow developers to quickly focus on testing their APIs.
  5. Real-Time Debugging: Apidog's real-time debugging features provide insights into the entire OAuth flow. Developers can inspect request and response details, aiding in diagnosing issues during testing.
  6. Documentation and Sharing: Apidog eases collaboration through shared collections. Developers can document OAuth configurations within collections, enabling seamless sharing of test scenarios and authorization configurations.
Apidog's Features for OAuth

The OAuth 1.0 authentication parameter values include:

  • Signature Method - The method the API uses to authenticate requests.
  • Consumer Key - A value to identify the consumer with the service provider.
  • Consumer Secret - A value for the consumer to establish ownership of the key.
  • Access Token - A value representing the consumer's permission to access user data.
  • Token Secret - A value for the consumer to establish ownership of a given token.
  • Private Key - A private key to generate the authentication signature.
imgAdvanced Parameters

Advanced Parameters in Apidog:

  • Callback URL - The URL the service provider will redirect to after user authorization.
  • Verifier - The verification code from the service provider after user authentication.
  • Timestamp - The timestamp the server uses to prevent replay attacks.
  • Nonce - A random string generated by the client.
  • Version - The OAuth authentication protocol version (1.0).
  • Realm - A string specified by the server in the WWW-Authenticate header.
  • Body Hash - Hash for integrity check with non-form-encoded request bodies.
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