Flowchart template

OAuth 2.0 Authorization Flowchart Template

A flowchart template illustrating the OAuth 2.0 authorization code grant flow, ideal for developers and architects documenting secure API authentication.

This flowchart template maps every step of the OAuth 2.0 Authorization Code Grant flow, from the initial user login request through the authorization server redirect, code exchange, token issuance, and final access to a protected resource. Each decision point—such as whether the user grants or denies consent, or whether the authorization code is valid—is clearly represented, giving developers, security engineers, and solution architects a precise visual reference for how the protocol operates end to end. The template covers all key actors: the resource owner (user), the client application, the authorization server, and the resource server.

## When to Use This Template

Use this flowchart when you need to document, explain, or audit an OAuth 2.0 implementation that relies on the authorization code grant—the recommended flow for server-side web applications and any scenario where client secrets can be kept confidential. It is especially useful during onboarding new engineers to an existing auth system, preparing security review documentation, or designing a new integration with a third-party identity provider such as Google, GitHub, or Okta. Teams building public-facing APIs that third-party developers will consume will also find this diagram invaluable for developer portal documentation.

## Common Mistakes to Avoid

One of the most frequent errors when diagramming this flow is omitting the PKCE (Proof Key for Code Exchange) extension, which is now recommended even for confidential clients. If your implementation uses PKCE, make sure the code challenge and code verifier steps are included in the flowchart. Another common mistake is conflating the authorization code with the access token—these are distinct artifacts exchanged at different steps, and your diagram should make that separation explicit. Avoid collapsing the token endpoint call and the resource server call into a single step, as this obscures a critical security boundary. Finally, always show the token expiry and refresh token flow as a separate branch; leaving it out gives an incomplete picture of how long-lived sessions are maintained securely.

View OAuth 2.0 Authorization as another diagram type

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FAQ

What is the OAuth 2.0 Authorization Code Grant flow?
The Authorization Code Grant is an OAuth 2.0 flow where the client redirects the user to an authorization server, receives a short-lived authorization code, and exchanges it for an access token via a secure back-channel request. It is the most secure grant type for server-side applications.
How does a flowchart help when implementing OAuth 2.0?
A flowchart provides a step-by-step visual of every actor, request, and decision in the protocol, making it easier to spot missing steps, misplaced logic, or security gaps before writing a single line of code. It also serves as shared documentation for cross-functional teams.
Should I include PKCE in my OAuth 2.0 Authorization Code flowchart?
Yes. PKCE (Proof Key for Code Exchange) is now recommended by OAuth 2.0 Security Best Current Practice for all clients, including confidential ones. Add the code_challenge parameter to the authorization request step and the code_verifier to the token exchange step in your flowchart.
What is the difference between the authorization code and the access token in this flow?
The authorization code is a temporary, single-use credential returned by the authorization server to the client's redirect URI. The access token is a longer-lived credential obtained by exchanging the authorization code at the token endpoint and is used to access protected resources.