Regex Tester & Validator

This regular expression matches valid Base64 encoded strings. It verifies that the string consists only of the standard Base64 alphabet (A-Z, a-z, 0-9, +, /) and has proper length with optional padding of one or two '=' characters. The regex ensures the total length is a multiple of four, which is required for well-formed Base64. Common use cases include validating Base64 data in APIs, configuration files, or data URI schemes.