JWT デコーダ オンライン — 無料でトークンのヘッダーとペイロードをデコード
JSON Web Token をブラウザでデコードしてヘッダーとペイロードを確認。署名の検証は行いません — デバッグ用です。
JWT を下に貼り付けてください。ヘッダーとペイロードは Base64URL からローカルでデコードされ、トークンはページから出ません。
よくある利用例
- 1Inspect an OAuth access token to check its expiration, audience and scopes.
- 2Debug a third-party SSO failure by reading the claims the IdP signed.
- 3Verify your app emits the JWT shape you expect before integration testing.
よくある質問
Why isn't the signature verified?+
Verification needs the issuer's public key (RS256 / ES256) or shared secret (HS256). That is an infrastructure decision — use jose / jsonwebtoken with the right key for that. This tool decodes only.
Is my token safe to paste here?+
Decoding runs entirely in your browser; the token never leaves the page. However, an ACTIVE access token still carries your identity — if it is in use, redact sensitive claims after debugging.
Why does my token decode to gibberish?+
It is probably not a JWT. Real JWTs always have three Base64URL parts separated by dots (header.payload.signature). Opaque tokens (random strings) do not decode to JSON.