Online JWT Decoder

A JSON Web Token (JWT) is a compact and URL-safe format for securely transferring claims between two parties. The claims in a JWT are encoded as a JSON object, which serves as the payload of a JSON Web Signature (JWS) structure or as the plaintext of a JSON Web Encryption (JWE) structure. This enables the claims to be digitally signed or integrity protected with a Message Authentication Code (MAC) and encrypted. JWTs are commonly utilized for authentication and authorization purposes, ensuring the secure transmission of information between parties.

JWT（JSON Web Token）は通常3つの部分を含んでいます：

• - ヘッダー：これは通常、トークンタイプ（つまりJWT）と使用されている署名アルゴリズム（HMAC SHA256やRSAなど）の2部分で構成されます。
• - Payload: This contains the claims. Claims are statements about an entity (typically, the user) and additional data. There are three types of claims: registered, public, and private claims. Registered claims include predefined claims such as iss (issuer), exp (expiration time), sub (subject), and aud (audience). Public claims can be defined at will by those using JWTs. Private claims are custom claims created to share information between parties that agree on using them.
• - Signature: To create the signature part, you have to take the encoded header, the encoded payload, a secret, the algorithm specified in the header, and sign that. The signature is used to verify that the sender of the JWT is who it says it is and to ensure that the message wasn't changed along the way.

The JWT Decoder is a convenient online tool for decoding and verifying JSON Web Tokens. Simply paste a JWT into the input field, and the tool will decode the header and payload, displaying their contents as JSON objects. This tool is helpful for understanding the structure, claims, and signature of JWTs, which is crucial for secure authentication and authorization in web applications.

JSON Web Tokens (JWTs) are frequently utilized for authentication and authorization in web applications. They serve as access tokens, enabling a user to access particular resources on a server following successful authentication. Moreover, JWTs can facilitate single sign-on (SSO) processes, allowing a user to log in to multiple services with a single authentication event. Additionally, JWTs can securely transmit information between two parties, guaranteeing the integrity and authenticity of the data.

JWTを使用する際には、その安全な処理と保管が非常に重要です。覚えておくべきいくつかの安全上の考慮事項には：

• - JWTの伝送には常にHTTPSを使用して、盗聴や中間者攻撃を防ぎます。
• - JWTをクライアント側で安全に保存する、例えばHttpOnly cookieに保存して、クロスサイトスクリプティング（XSS）攻撃を防ぐ。
• - 不正アクセスを防ぐために、適切なトークンの有効期限と取り消しメカニズムを実装します。
• - RS256（RSAとSHA-256）のような強力な署名アルゴリズムを使用して、偽造を防ぎます。
• - JWTペイロード内のすべてのクレームを検証して、その正確性と真実性を確保します。