Decode JWT headers and payloads to inspect claims, expiry, and algorithms with signature highlighting and safe client-side parsing without uploads offline.
Part of our Developer Tools collection — Explore more Developer Tools tools · See also: JSON Formatter, Base64 Encode / Decode.
Quick answer: JWT Decoder — Decode JSON Web Tokens safely Free, no signup, runs in your browser. See below for the interactive tool, 4-step guide and FAQs.
Decoding is local; 0 / 1,000,000 chars — nothing sent anywhere.
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No. It solely reveals header and payload for inspection, while genuine assurance demands secret or public key checks inside your services. For illustration, a test token displaying alg HS256 and sub 123 can be forged by anyone. Treat decoded views as diagnostic hints, then validate signatures in backend code before granting access or trusting roles.
No. Token parsing executes solely inside this tab, so a three-part sample holding 24 claims never traverses networks. For instance, demo values remain resident, function. The tool works entirely offline in your browser and forgets everything on close. Prefer brief test tokens and shutter the tab afterward for hygiene.
Yes. It interprets exp and iat numeric claims against device clock to label active, expiring, or stale sessions. For example, exp 1717252800 two hours past present renders as expired 2h ago with localized timestamp. A 24-claim sample evaluates within fifty milliseconds. Decoding never equals verification; confirm signatures with secrets in controlled code paths.
Audience checks compare aud claim against expected service identifiers to catch cross-environment reuse. For example, staging token presenting prod audience signals misconfiguration before deployment. Inspect iss, aud and scope claims side by side, rotate test keys frequently, and redact emails from screenshots. Reproduce with synthetic users rather than customer tokens to preserve confidentiality across support tickets.
A token strings three Base64 segments with dots: header, payload and signature, resemblingaaa dot bbb dot ccc. Example 1: header declares typ JWT and alg HS256 for HMAC protection. Example 2: payload carries sub 123 identifying a user, iat marking issuance and exp 1717245600 marking June 1 2024 expiry. Servers verify signature with secrets, clients read claims for interface decisions. Audience, issuer and scope fields scope permissions. Recognizing structure helps diagnose truncated copies, misplaced line breaks and confusion between access and refresh tokens during integration across mobile and web clients. Clinics rotating test users and ephemeral keys rehearse expiry handling without exposing customer emails across support channels while capturing traces for audits across staging environments daily for safety now daily.
Reference claim table: alg names signing method | typ marks JWT media | sub identifies subject 123 | iat records issued time | exp records expiry 1717252800 | aud scopes audience. The panel contrasts exp and iat against device clock, flagging active, expiring within minutes, or stale by hours. Decoding never proves authenticity; verification requires secret or public key on trusted servers. Edge case: alg none tokens carry no signature, so reject them in production. Clock skew beyond thirty seconds mimics expiry, demanding NTP synchronization across distributed issuers and validators.
Paste sample with header alg HS256 and payload sub 123, observe decoded JSON with claims expanded, then copy excerpt for ticket context. Second trial: inspect exp 1717252800, note expired 2h status, adjust test clock or mint fresh token. Limitation: display only, no cryptographic assurance, and prod tokens pasted on shared screens expose emails and roles. For time math around expiry windows, see the converter at /timestamp-converter for epoch translation. For payload transport encoding basics, see the tool at /base64-tool for segment mechanics. Second drill minting short-lived tokens with aud scopes validates audience checks, while archiving redacted samples accelerates future triage across teams.