What problem does this solve?
Developers need to understand JWT fields such as alg, typ, sub, iss, exp and nbf. A token that decodes successfully is NOT a token whose signature, issuer, audience or authorization have been checked.
JWT Header & Payload Decoder
Inspect the JSON inside a disposable JSON Web Token without sending it to a server or pretending its signature is valid.
Never paste production passwords, live JWT access tokens or private customer records.
Try it with a fictional sample
Token structure inspectionNo uploads, cookies, tracking or third-party scripts. Your input stays in browser memory.
Output
LOCALReady. Enter a test value.
How to use it
Use the fictional example or paste a disposable three-part token. The tool base64url-decodes the first two segments into readable JSON, reports expiry/not-before claims relative to your device clock, and explicitly leaves signature verification undone.
Scope and limitations
Never paste real access tokens, refresh tokens or customer authentication data into websites. This source-visible browser-only decoder has no network requests, but decoded payloads are untrusted JSON. Claims alone never prove token authenticity.
Common questions
Is a decoded JWT valid?
No. Decoding is not signature verification. The tool does not verify alg keys, issuer, audience, intended use or revocation.
Does it use my OpenAI or Shopify account?
No. No token is transmitted or used for an API call. Use fictional test tokens only.
Does exp equal the true logout time?
Not necessarily. The exp claim is inside unverified payload data and your device clock may be inaccurate; a server can reject a token earlier.