Space-free text is useful for compact identifiers, reference numbers, copied codes and exact string comparisons. The live two-panel layout keeps the source visible while showing the transformed result, so you can verify that punctuation, letters, numbers and emoji remain unchanged.
Spaces and tabs is the safer default because it preserves the original line structure. All whitespace also removes carriage returns, line feeds and Unicode line separators. Both modes run locally in your browser, with no upload or account.