Apoptotic adapter molecule that recruits caspases CASP8 or CASP10 to the activated FAS/CD95 or TNFRSF1A/TNFR-1 receptors (PubMed:16762833, PubMed:19118384, PubMed:20935634, PubMed:23955153, PubMed:24025841, PubMed:7538907, PubMed:9184224). The resulting aggregate called the death-inducing signaling complex (DISC) performs CASP8 proteolytic activation (PubMed:16762833, PubMed:19118384, PubMed:20935634, PubMed:7538907, PubMed:9184224). Active CASP8 initiates the subsequent cascade of caspases mediating apoptosis (PubMed:16762833). Involved in interferon-mediated antiviral immune response, playing a role in the positive regulation of interferon signaling (PubMed:21109225, PubMed:24204270). {ECO:0000269|PubMed:16762833, ECO:0000269|PubMed:19118384, ECO:0000269|PubMed:20935634, ECO:0000269|PubMed:21109225, ECO:0000269|PubMed:23955153, ECO:0000269|PubMed:24025841, ECO:0000269|PubMed:24204270, ECO:0000269|PubMed:7538907, ECO:0000269|PubMed:9184224}. This is the function of FADD (Fas associated via death domain, ENSG00000168040).