Implementing the OAuth client using a library

Many open source libraries offer high-quality implementations of OAuth clients. They are available in a variety of programming languages, offering support for various web frameworks and database backends.

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Where to start

A list of open-source OAuth client libraries is available at https://oauth.net/code/.

We strongly recommend using one of these libraries instead of trying to implement OAuth from scratch

Implementing the client using a library

Libraries providing OAuth implementation often allow for some degree of customisation, allowing to plug in custom implementations for front-end and back-end interfaces they provide.

Most often, when using a library, a developer can:

• configure the client for use with specific authorization server: provide the authorization and token endpoints, configure supported client authentication methods and protocol extensions;
• provide the UI for initiating the flow (”Connect to Pleo” button), and connect it to functions and methods of the library that generate all necessary authorization request parameters;
• integrate the library with the web framework of choice to allow it to perform HTTP redirects;
• provide implementation for persistence backend, allowing the client library to store and retrieve parameters, such as code_verifier and state, as well as access and refresh tokens;
• provide custom UI for handling success and error responses from the authorization server;
• listen to events emitted during flow, and extend various stages.

Exact details and capabilities vary between implementations. Consult the documentation of the library of your choice.