Security Tools
Base64 Decoder
Decode Base64 encoded strings back to plain text instantly.
JWT Decoder
Decode, inspect, and validate JSON Web Tokens (JWT) client-side instantly. Split tokens into their color-coded Header, Payload, and Signature components, translate Unix epoch timestamp claims (like exp, iat, nbf) into human-readable local dates, and check expiration status.
Security check: Base64 decoding happens locally in your browser. No data is sent to external APIs.
What is the JWT Decoder?
The FreeTechLearner JWT Decoder translates JSON Web Tokens entirely within the client browser. It breaks down encoded tokens, parses headers and payloads, translates timestamp claims, and provides structure validation and expiration badges.
How to Use
- Paste your encoded JSON Web Token (JWT) into the input textarea.
- The tool splits the token into three color-coded sections (Header in red, Payload in purple, Signature in green).
- Review the formatted JSON output for the Header and Payload.
- Check the translated claims section to see when the token was issued, activated, or expired.
- Copy any individual section or the entire decoded JSON as needed.
Common Use Cases
- Debugging OAuth2 or OpenID Connect authentication tokens
- Checking JWT scopes, roles, user IDs, and permissions
- Verifying token expiration times and issuance dates during local testing
- Inspecting token header algorithms and key IDs (kid)
Key Benefits
- 100% browser-based execution — token content never leaves your machine
- Color-coded token segment mapping matching industry standards
- Human-friendly claims translator (auto-converts epoch times)
- Instant copy shortcuts for individual header and payload parts
Frequently Asked Questions
Is it safe to paste my JWT here?
Yes, absolutely. Our JWT decoder operates 100% in your local browser using client-side JavaScript. No tokens, keys, or personal details are uploaded or transmitted to any server. However, you should still practice caution with highly sensitive production tokens in any online web utility.
Does this tool verify the cryptographic signature of the token?
This tool decodes the Base64Url-encoded Header and Payload to inspect claims, and validates the token structure. It does not perform cryptographic signature verification against a public key or secret, as verifying signatures requires server keys.
How do I know if my token is expired?
The tool checks the "exp" (expiration) claim in the token payload. If the expiration timestamp is in the past compared to your current system time, it displays a red "Expired" status badge. If it is still valid, it displays a green "Active" badge.
What are standard claims like iss, sub, and aud?
These are standard JWT claims: "iss" (Issuer) identifies who created the token; "sub" (Subject) identifies the user or client the token belongs to; "aud" (Audience) identifies the recipients that the token is intended for.
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