JWT Decoder
Decode and inspect JSON Web Tokens (JWT) locally in your browser. Inspect header parameters, payload claims, and token expiration timestamps without transmitting data over the network.
Decoding a JWT simply extracts and inspects the Base64Url-encoded JSON payload in your browser. Decoding does NOT verify the cryptographic signature or prove token authenticity. Anyone can forge a token with arbitrary claims. Always verify the signature with your secret key or public certificate on your secure server before granting permissions or authorizing requests.
{
"alg": "HS256",
"typ": "JWT"
}{
"sub": "usr_12890",
"name": "Alexander Reyes",
"email": "alex@example.com",
"role": "admin",
"iat": 1516239022,
"exp": 1916239022
}Inspect JSON Web Token Claims Locally & Safely
Understanding JWT structure, Base64Url encoding, and signature verification
JSON Web Tokens (RFC 7519) are compact, URL-safe security credentials used for client-side authentication and stateless API authorization. A JWT consists of three parts concatenated with periods: a Header (identifying the signing algorithm), a Payload (containing user identity and permission claims), and a cryptographic Signature.
Because headers and payloads are merely Base64Url-encoded strings (not encrypted), anyone in possession of the token can decode its contents. However, decoding alone does not prove authenticity. A malicious actor can easily modify claims and construct a forged token.
Modifyle lets software engineers, security analysts, and QA teams inspect token payloads safely inside their local browser without sending production authentication credentials to third-party debugging websites.
What Can You Use This Tool For?
Real-world problems solved and intended workflows for this tool.
Decoded Token Inspection Without Secret Exposure
Inspect JSON Web Token (JWT) headers, claims, and payload properties locally in browser memory without sending authentication tokens across the internet.
Token Expiration & Issuer Claim Verification
Verify exp, iat, and nbf timestamps converted to human-readable local times to diagnose token expiration and session termination issues.
Role & Permission Scope Validation
Audit user roles, tenant IDs, and RBAC permission arrays embedded inside token payloads to confirm authorization configurations.
How It Works in 3 Simple Steps
Paste Encoded Token
Paste your JWT string (beginning with eyJ...) into the input field.
Review Header & Claims
Inspect the signing algorithm, user roles, issued-at date, and expiration timestamp.
Verify Expiry Status
Check whether the token is currently active or expired based on the standard exp claim.
- Processing executes locally in browser memory. Large files depend on available device RAM and CPU capacity.
Why choose Modifyle JWT Decoder?
Launch PDF, image, and QR tools in 1 click right from your home screen or desktop dock. 100% private, client-side, with full offline capability without internet.