Base64 Validator

The Base64 Validator checks a Base64 string or data URI and returns a clear verdict plus a breakdown of characters, padding, and any problems. It is for developers confirming that encoded data is well-formed.

Invalid Base64 fails silently or with a vague error elsewhere. Validating it locally gives an immediate, specific verdict without uploading the data.

1. Paste a Base64 string or data URI.
2. The validator checks the characters and padding.
3. Read the verdict and the breakdown of any issues.
4. Fix the input and re-check if needed.

• Valid or invalid verdict
• Character and padding breakdown
• Problem explanations
• Runs in the browser — Base64 Validator

• Confirming a Base64 payload is well-formed before decoding
• Diagnosing why a string fails to decode elsewhere
• Checking padding on a value that looks truncated
• Validating data URIs during development

• Strip whitespace and line breaks before validating a single string.
• Check whether the value should be standard or URL-safe Base64.
• Confirm padding is correct, since wrong padding is a common failure.

• Missing that stray whitespace or line breaks invalidate a string.
• Confusing standard and URL-safe alphabets, which use different characters.
• Overlooking incorrect padding, which the validator highlights.