JWTデコーダー
JWTトークンをオンラインでデコード・検証します。JWTヘッダー、ペイロード、署名情報を表示します。
JWTトークン
機能紹介
The JWT Decoder tool lets you inspect JSON Web Tokens by decoding their header, payload, and signature parts. It is ideal for debugging authentication bugs, checking claims, and understanding token structure.
このツールを使うタイミング
Use this tool whenever you work with JWT-based authentication: verifying token contents, debugging expired or invalid tokens, or learning how JWTs are structured.
使い方
Paste your JWT
Copy a full JWT (three dot-separated sections) from your application or API client and paste it into the input field.
Decode the token
The tool automatically decodes the header and payload from Base64URL, showing you the JSON content in a readable format.
Inspect claims and metadata
Review fields such as issuer, subject, audience, and expiration to verify that the token matches your expectations.
Use the decoded data for debugging
Compare decoded values with your server-side configuration when troubleshooting authentication or authorization issues.
使用例
Checking why a user is unauthorized
Decode the user's token to confirm whether required roles or permissions are present in the payload.
Verifying token expiry
Quickly check the exp claim to see whether a token has expired or is close to expiry.