🔑JWT & Auth

PKCE Code Verifier

Securing mobile and single-page apps during OAuth flow.

Explanation

PKCE prevents authorization code injection attacks by requiring a secret "challenge" verified at exchange.

Examples

Flow
Output
Verifier -> Challenge (SHA256) -> Exchange

Code Examples

JavaScript 
// 1. Generate Verifier (random string)
const verifier = generateRandomString(64);

// 2. Create Challenge
const challenge = crypto.createHash('sha256')
  .update(verifier)
  .digest('base64url');

💡 Tips

  • Required for modern mobile and SPA apps
  • The verifier must be between 43 and 128 characters
  • Use "S256" as the code_challenge_method

⚠️ Common Pitfalls

  • Using the "plain" method which is less secure
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