Infidelity is more than extradyadic intercourse, but it is unclear where infidelity begins and how behaviors are related to each other. We investigated data from a factorial survey experiment implemented in the German Family Panel (pairfam). 9,104 respondents evaluated 26,633 vignettes on unfaithful behaviors including four dimensions: explicit behavior, emotional involvement, infidelity duration, and erotic online contact. Results suggest that item lists may not reveal the full picture of unfaithfulness. While intercourse is judged as unfaithful irrespective of the context, less explicit behaviors such as kisses or hugs were also regarded as infidelity. Nonphysical dimensions contributed to infidelity judgments more strongly when less explicit behaviors were evaluated. Even cases of no physical contact combined with erotic text messages and emotional involvement were evaluated as unfaithful. Women's judgments were stricter than men's, and younger respondents' evaluations were stricter than those from older respondents. No differences were found regarding the gender of the vignette character.