Regex Tester & Validator

Validates a complete Base64-encoded string that must end with = or == padding, allowing an optional newline after each 4-character group, as found in GPG armored or line-wrapped Base64 output. Anchored with ^ and $, it consumes full 4-character quanta before requiring a final padded group of 2 or 3 characters. Useful for checking wrapped Base64 blocks, though it rejects unpadded Base64 whose length is already a multiple of four.