Frequently Asked Questions

This section answers common questions about the JWT Parser tool and JWT tokens in general.

General Questions

What is a JWT?

JWT (JSON Web Token) is an open standard (RFC 7519) that defines a compact and self-contained way for securely transmitting information between parties as a JSON object. It's commonly used for authentication and information exchange.

What does this tool do?

The JWT Parser tool parses and decodes JWT tokens to display their header, payload, and signature in a readable format. It helps developers understand token structure and debug authentication issues.

Is this tool secure?

Yes, the tool is designed with security in mind:

• All processing happens in your browser
• No data is sent to external servers
• History is stored locally in your browser only
• You can clear all data at any time

Usage Questions

How do I use the tool?

1. Paste your JWT token in the input field
2. The tool automatically parses the token
3. Review the parsed header, payload, and signature
4. Use the copy button to save results

What format should my JWT be in?

JWT tokens should be in the standard format: header.payload.signature with exactly 2 dots separating the 3 parts.

Can I use any JWT token?

Yes, the tool can parse any valid JWT token. However, for security reasons, you should only use test or development tokens, never production tokens.

Does the tool validate tokens?

No, the tool only parses and displays token contents. It does not validate signatures, check expiration, or verify claims. It's purely for analysis and debugging.

Technical Questions

What algorithms are supported?

The tool can identify and display information about all standard JWT algorithms:

• Symmetric: HS256, HS384, HS512
• Asymmetric: RS256, RS384, RS512, ES256, ES384, ES512
• None: Unsecured tokens (development only)

How does the tool handle large tokens?

The tool can handle tokens up to browser memory limits. For very large tokens, processing may take longer, but the tool will attempt to parse them.

What happens if a token is invalid?

The tool will display an appropriate error message:

• "Invalid JWT format" for structural issues
• "Failed to parse JWT token" for parsing errors

Can I parse expired tokens?

Yes, the tool can parse expired tokens. It will display the expiration time and indicate if the token has expired.

Security Questions

Is my token data safe?

Yes, your token data is safe:

• All processing happens in your browser
• No data is transmitted to external servers
• History is stored locally in your browser
• You control all data and can clear it anytime

Should I use production tokens?

No, you should never use production tokens with this tool. Only use test or development tokens for security reasons.

Can I share parsed results?

You can share parsed results, but be careful:

• Only share test token examples
• Never share production token data
• Be aware of any sensitive information in claims

What about sensitive claims?

Be aware that JWT tokens may contain sensitive information in their claims. Only parse tokens that you own or have permission to analyze.

History and Storage

How does history work?

The tool automatically saves parsed tokens to your browser's local storage:

• Limited to 50 recent tokens
• Persists across browser sessions
• Stored locally in your browser only
• You can clear history at any time

Can I disable history?

Currently, history is always enabled. You can clear it manually using the "Clear History" button.

Is history shared between devices?

No, history is stored locally in each browser and is not shared between devices or browsers.

How long is history kept?

History is kept until you clear it manually or until you reach the 50-token limit (oldest tokens are automatically removed).

Error Handling

What if I get an error?

Common errors and solutions:

• Invalid format: Check that your token has exactly 3 parts separated by dots
• Parse failed: Verify that each part is valid base64url encoding
• JSON error: Ensure header and payload are valid JSON

Why can't I parse my token?

Possible reasons:

• Token format is incorrect
• Token is corrupted or truncated
• Token contains invalid characters
• Token is not a valid JWT

How do I fix parsing errors?

1. Check token format (should have 2 dots)
2. Verify each part is valid base64url
3. Ensure header and payload are valid JSON
4. Try with a known good token first

Browser Compatibility

Which browsers are supported?

The tool works in all modern browsers:

• Chrome (recommended)
• Firefox
• Safari
• Edge

What if my browser doesn't work?

Make sure your browser:

• Supports local storage
• Has clipboard API support
• Can parse JSON
• Is up to date

Can I use it on mobile?

Yes, the tool works on mobile browsers, though the interface may be optimized for desktop use.

Performance

How fast is the tool?

The tool is very fast for typical JWT tokens:

• Most tokens parse instantly
• Large tokens may take a few seconds
• All processing happens in your browser

Does it work offline?

Yes, the tool works completely offline once loaded. No internet connection is required for parsing.

Are there any limits?

The tool can handle tokens up to browser memory limits. For very large tokens, you may experience slower performance.

Integration

Can I integrate this into my app?

The tool is designed as a standalone web application. For integration into your own app, you would need to implement JWT parsing functionality separately.

Is there an API?

No, this tool doesn't provide an API. It's a client-side web application for interactive use.

Can I use it in automated testing?

You can use the tool to generate test data for automated testing, but you'll need to implement JWT parsing in your test code.

Troubleshooting

The tool isn't working

Try these steps:

1. Refresh the page
2. Clear your browser cache
3. Check for JavaScript errors in console
4. Try a different browser

Copy function isn't working

Make sure:

• Your browser supports the clipboard API
• You've granted clipboard permissions
• You're using a secure context (HTTPS)

History isn't saving

Check that:

• Your browser supports local storage
• Local storage isn't disabled
• You're not in private/incognito mode

Display issues

Try:

• Refreshing the page
• Clearing browser cache
• Checking browser zoom level
• Using a different browser

Support

Where can I get help?

• Check this FAQ for common issues
• Review the documentation sections
• Look for error messages in the tool
• Check browser console for errors

How do I report issues?

If you encounter issues:

1. Check if it's a known problem in this FAQ
2. Try the troubleshooting steps
3. Note your browser and version
4. Describe the exact steps to reproduce

Is the tool open source?

The tool is part of a larger developer tools collection. Check the project repository for more information about the codebase.