The ultimate suite of AI-powered developer tools for modern engineering. Secure, local-first utilities for JSON formatting, JWT debugging, SQL beautification, and more.
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Free Online Developer Tools for Modern Engineering
GetDevUtils is a comprehensive suite of free developer tools designed for modern software engineers, web developers, and DevOps professionals. Our collection of online utilities helps you format, validate, convert, and analyze data instantly — all within your browser, with no installation required. Every tool is built with a privacy-first, local-processing approach, ensuring your sensitive data never leaves your device.
Whether you're debugging authentication tokens, formatting JSON responses, converting timestamps, or generating secure passwords, GetDevUtils provides professional-grade tools that work offline, respect your privacy, and integrate seamlessly into your development workflow.
Complete Developer Toolkit
GetDevUtils provides specialized tools across five categories to cover every aspect of modern web development:
JWT Verifier validates the signatures of JSON Web Tokens (JWTs) to ensure they haven't been tampered with. Unlike the JWT Debugger which only decodes tokens, JWT Verifier performs cryptographic verification using your secret (for HS256) or public key (for RS256/ES256). This is essential for debugging authentication flows and validating token integrity.
Why Use This Tool?
When debugging authentication issues, you need to verify if tokens are correctly signed. Common scenarios include: testing newly issued tokens, debugging "invalid signature" errors, validating tokens from third-party providers, and ensuring key configuration is correct. JWT Verifier performs this verification entirely in your browser - your secrets and tokens never leave your device.
How to Use JWT Verifier
Paste the complete JWT token
Select the algorithm used (HS256, RS256, ES256, etc.)
Enter the secret (for HMAC) or public key (for RSA/ECDSA)
Click "Verify" to check the signature
View decoded header and payload alongside verification result
Development Testing: Test token generation before deployment
Tips & Best Practices
✓ For RS256, you only need the public key to verify - never share private keys
✓ HS256 secrets should be at least 256 bits (32 characters) for security
✓ Check kid (Key ID) header claim when using JWKS with multiple keys
✓ Expired tokens (exp claim) will show as invalid signature
How It Compares to Alternatives
jwt.io allows signature verification but sends tokens to Auth0's servers. JWT Verifier performs all cryptographic operations locally using the Web Crypto API. Unlike library-based verification, it provides a visual interface for debugging.
Frequently Asked Questions
How do I verify a JWT signature?
Paste your JWT token and enter the secret (for HS256) or public key (for RS256/ES256). Click Verify to check if the signature is valid and hasn't been tampered with.
What algorithms are supported?
We support HS256, HS384, HS512 (HMAC), RS256, RS384, RS512 (RSA), ES256, ES384, ES512 (ECDSA), and PS256, PS384, PS512 (RSA-PSS).
Is my secret key safe?
Absolutely! All verification happens locally in your browser. Your secret keys and tokens are never sent to any server. Check your network tab to verify.
Ready to Get Started?
Use JWT Verifier for free - no registration required.