JWT Decoder
Decode JWT header and payload locally (no network, no verification).
JWT decoder
Loading the interface for inspecting JWT headers, payloads, and verifying HS256 signatures.
About this tool
The Gearizen JWT Decoder helps developers and security auditors inspect JSON Web Tokens without transmitting them to any server. Paste a JWT and instantly view the header and payload decoded from Base64URL, along with syntax highlighting that clarifies algorithms, expiration claims, and custom metadata. Because verification keys are never requested, you can safely review tokens taken from staging environments, customer reports, or API logs while staying compliant with security policies. This tool is indispensable when debugging authentication flows, analyzing third-party integrations, or teaching teammates how stateless tokens work.
Throughout this page, we explain how JWTs are structured, why algorithms like HS256 and RS256 matter, and how to interpret standard claims such as iss, sub, exp, and aud. We also clarify the limitations: decoding does not validate signatures, so we provide guidance on how to confirm authenticity using our related Hash & HMAC Generator or your backend frameworks. Troubleshooting sections cover clock skew, token revocation strategies, and common vulnerability patterns like token substitution or missing audience checks.
SEO-friendly chapters answer questions like "How do I decode a JWT?" and "Is it safe to share a JWT?" We offer best practices for storing tokens, discuss secure cookie usage, and outline how to rotate signing keys without breaking clients. Whether you are building single-page applications or server-to-server integrations, the decoder helps you visualize payloads, document claims, and communicate security expectations clearly.
Complete your token workflow with the Base64 Encoder for manual claim editing, the Password Generator for creating signing secrets, and the Hash & HMAC Generator for validating HMAC-based signatures. These related tools create a cohesive suite for identity engineering. Bookmark the JWT Decoder whenever you need to understand token contents fast, educate stakeholders, or prepare SEO-optimized documentation around authentication best practices.
Advanced tutorials walk through decoding signed tokens in CI pipelines, annotating claims for customer support escalations, and documenting scopes for OAuth providers. By following these workflows, your team gains a repeatable playbook for secure JWT analysis.
How to use
Paste the JWT
Add the full token including header, payload, and signature segments.
Decode the segments
Let the tool decode Base64URL data and present the header and payload in JSON form.
Review claims and metadata
Inspect algorithms, expiration times, and custom claims to understand token behavior.
Plan validation steps
Document how you will verify the signature and enforce claims inside your application.
Examples
| Scenario | Input | Output | Notes |
|---|---|---|---|
| Inspect expired token | JWT with past exp | Payload showing exp timestamp | Explains why authentication failed. |
| Review scopes | JWT with scope claim | Decoded scope array | Helps confirm authorization levels. |
| Check algorithm mismatch | JWT header alg=none | Header highlighting insecure alg | Flags tokens requiring remediation. |
Help & FAQ
Do you verify signatures?
No. This tool only decodes header and payload for inspection.
Base64URL?
JWT segments are Base64URL encoded (URL-safe, no padding).