Base64 Validator checks character set, length multiples of 4, padding, and atob() decode success with clear error messages.
Base64 Validator
Validate Base64 Free
Check Base64 or Data URLs for invalid characters, length, padding, and decodeability - live as you type.
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What is this?
How it works
1. Paste Base64 or a Data URL.
2. Validation runs automatically (300ms debounce).
3. See a green or red result with details.
4. Optionally open the same text in the Base64 codec to decode.
Features
- Live validation
- Data URL MIME detection
- Error position
- Approx decoded size
- Handoff to Base64 codec
Benefits
Catch broken Base64 before it breaks your app or download.
Trust & privacy
Validation runs locally. Nothing is sent to a server.
Frequently asked questions
It opens /tools/base64-codec in decode mode with your text prefilled.
Whitespace is ignored when checking the Base64 payload.