Validate Base64 Tool

Base64 validation typically involves checking that the input string meets the expected format and contains only valid base64 characters. This is usually done by first checking that the input string has a length that is a multiple of 4, since base64 encoding always results in output strings that are a multiple of 4 characters long. Next, the input string is checked to ensure that it only contains characters that are valid base64 characters, which are typically the 26 uppercase and lowercase letters of the alphabet, the 10 digits, and the '+' and '/' symbols.

Any characters that are not valid base64 characters will cause the validation to fail. Additionally, some base64 implementations may require padding characters ('=') to be present at the end of the input string to ensure that it has the correct length, so the validation may also check for the presence and placement of padding characters.