Security & Quality

OAuth2 Authorization Flows

Implement OAuth2 authorization code, PKCE, and client credentials flows with the oauth4webapi library.

Claude Code Cursor Copilot

Overview

oauth4webapi is a modern, lightweight OAuth 2.0 and OpenID Connect library that uses the Web APIs (Fetch, Web Crypto) and follows the latest security best practices. It supports Authorization Code with PKCE, Client Credentials, Device Authorization, and Token Refresh flows, all built on standards-compliant implementations.

Unlike older OAuth libraries, oauth4webapi is runtime-agnostic, working in Node.js, Deno, Cloudflare Workers, and browsers. It implements the latest OAuth 2.0 Security Best Current Practice (BCP) recommendations, including mandatory PKCE, issuer identification, and DPoP (Demonstration of Proof-of-Possession). The library avoids legacy features and insecure patterns by design.

The library provides low-level building blocks rather than opinionated abstractions, giving developers full control over the OAuth flow. It handles discovery document parsing, token endpoint requests, token introspection, and userinfo endpoint calls. For OpenID Connect, it validates ID tokens, handles nonce verification, and supports all standard claims.

Who Is This For?

Implement OAuth2 Authorization Code + PKCE flow
Set up Client Credentials flow for service-to-service auth
Build OpenID Connect login with ID token validation
Handle token refresh with rotation detection

Installation

Setup for Claude Code

npm install oauth4webapi

Configuration

import * as oauth from "oauth4webapi"

const issuer = new URL("https://accounts.google.com")
const as = await oauth.discoveryRequest(issuer)
  .then((res) => oauth.processDiscoveryResponse(issuer, res))

const client = { client_id: "your-client-id" }
const codeVerifier = oauth.generateRandomCodeVerifier()
const codeChallenge = await oauth.calculatePKCECodeChallenge(codeVerifier)