JWT Expiry Checker Online — Decode & Check Token Expiration Free

What Is a JWT and How Does Expiry Work?

JWT (JSON Web Token) is a compact, URL-safe token format used to securely transmit claims between parties. A JWT consists of three Base64URL-encoded parts separated by dots: header.payload.signature.

The payload contains claims — key-value pairs about the subject (typically a user) and the token itself. The two most important time-related claims are:

• exp (expiration time): A Unix timestamp (seconds since epoch) after which the token must not be accepted.
• iat (issued at): The Unix timestamp when the token was issued.
• nbf (not before): Optional. The token should not be accepted before this time.

When a JWT expires, API calls return 401 Unauthorized errors. Checking the token's exp claim instantly tells you whether expiry is the cause of the problem.

How to Check JWT Expiry Online

1. Open the JWT expiry checker at DevKits.
2. Paste your JWT token into the input field.
3. The tool decodes the header and payload automatically, without needing the signing secret.
4. View the expiry details: exp timestamp, formatted expiry date/time, and whether the token is currently valid or expired.
5. See the time remaining or time since expiry displayed in human-readable format.

Example JWT Payload (decoded)

{
  "sub": "user_12345",
  "iat": 1741824000,   // issued: 2026-03-13 00:00:00 UTC
  "exp": 1741910400,   // expires: 2026-03-14 00:00:00 UTC
  "roles": ["admin"]
}

Key Features

• Full JWT decoding — header, payload, and algorithm displayed in formatted JSON.
• Expiry status indicator — clear valid / expired / not yet valid status with color coding.
• Human-readable timestamps — Unix timestamps converted to local and UTC time.
• Remaining time counter — live countdown showing time until expiry.
• No secret required — decodes the payload without needing the signing key.
• 100% client-side — your token never leaves your browser.

Use Cases

Debugging Authentication Errors

When an API returns 401 Unauthorized, expired tokens are one of the most common causes. Pasting the token into the expiry checker instantly confirms whether this is the issue — saving time compared to adding console.log statements or writing a decode function.

Monitoring Token Lifetimes

Different JWT issuers set different expiry windows: short-lived access tokens (15 minutes), longer refresh tokens (7 days), or even longer API keys (1 year). Checking the exp field helps understand what lifetime your auth provider is issuing and whether it matches your application's requirements.

Development and Integration Testing

When integrating a new OAuth provider or authentication service, decoding the JWT confirms that the claims match your expectations — the right user ID, roles, scopes, and expiry time are all present.

Security Auditing

A JWT expiry checker can identify tokens with dangerously long expiry windows (e.g., tokens that never expire) or tokens missing the exp claim entirely — both security risks that should be flagged in a security review.

Understanding JWT Structure

The three parts of a JWT, when decoded, reveal:

• Header: Signing algorithm (alg) and token type (typ). Common algorithms: HS256 (HMAC-SHA256), RS256 (RSA), ES256 (ECDSA).
• Payload: The claims. Standard claims include sub (subject), iss (issuer), aud (audience), exp, iat, and custom claims.
• Signature: Cryptographic signature verifying the token's integrity. Cannot be decoded without the secret key.

Important: JWT payloads are Base64URL-encoded, not encrypted. Anyone with access to the token can read the claims. Never put sensitive data in a JWT payload unless it's encrypted (JWE).

Frequently Asked Questions

Do I need the JWT secret to check expiry?

No. The payload (including exp) is Base64URL-encoded and readable without the signing secret. The expiry checker decodes the payload directly. To verify the signature, you would need the secret.

Is it safe to paste my JWT into an online tool?

DevKits processes JWTs entirely in the browser — no token is sent to a server. However, as a general security practice, avoid pasting production tokens containing sensitive claims into any online tool. Use test tokens or tokens that have already expired when possible.

What if my JWT doesn't have an exp claim?

The tool will decode the payload and indicate that no exp claim is present. Tokens without expiry claims are valid indefinitely until revoked, which is a security concern.

How do I refresh an expired JWT?

Refreshing a JWT typically involves sending a refresh token to the authorization server's token endpoint to obtain a new access token. The implementation depends on your OAuth or authentication provider.

Is the tool free?

Yes, completely free with no account or signup required.