Base64 Validator

Check if a Base64 string is valid. Get detailed analysis including character set, padding, and MIME type detection.

Enter a Base64 string to validate

Paste a Base64 string above to validate it

Frequently Asked Questions

Got questions? We've got answers. Search below or browse through our most commonly asked questions.

A Base64 string can be invalid if it contains characters outside the allowed alphabet (A-Z, a-z, 0-9, +, /), has incorrect padding (=), or has a length that isn't a multiple of 4 (for standard Base64).

The Validator will tell you exactly what is wrong. If you need it automatically fixed, use our 'Base64 Repair Tool' which can add missing padding and strip illegal characters.