Before-and-after Base64 review: compare decoded content

A Base64 string can look very different after a small source change, so compare decoded bytes rather than eyeballing the encoded text. Check input encoding, whitespace, line endings, and whether padding or line wraps were added by the tool. If both strings decode to the same bytes, formatting alone may differ; if the bytes differ, inspect the source data. Base64 round-trip validation does not prove the decoded JSON, image, or document is semantically correct.