In 2017, the NHS 111 telephone service was augmented by an online service. This is an exemplar of 'digital-first', the push to enrol digital technologies to deliver services, and is viewed by policymakers as an important vehicle for managing demand for overburdened health services. This article reports the qualitative component of a larger multi-method study of NHS 111 online. Qualitative telephone interviews with 80 staff and stakeholders implicated in primary, urgent and emergency care service delivery explored the impact of NHS 111 online on health-care work. The analysis presented here draws on Susie Scott's work on the 'sociology of nothing' and theories of the marked and unmarked, which we reached for when confronted by the remarkable invisibility of this seemingly core NHS service in the wider landscape of health care. Despite the apparently high use by patients and the public (30 million visits over 6months in the 2020 pandemic), we were surprised to find very low awareness among our interviewees. Confusion about nomenclature, an exceedingly crowded digital field (littered with alternative technologies and ways of accessing care) and constant change in service provision provide some cogent reasons for this invisibility, and sociology helps explain our data about this digital technology.