Teachers naturally engage in the act of 'noticing' as part of their daily practice. This specialised form of noticing, referred to as 'teacher noticing', involves a deliberate focus on specific aspects within the mathematics classroom. The author's PhD research has investigated how the events teachers notice and respond to online in Emergency Remote Teaching (ERT) compare to the face-to-face classroom environment. In the face-to-face classroom, noticing and responding can occur quickly, with teachers interpreting observations and making decisions in the moment. However, teachers discovered that noticing and responding went from a matter of minutes to over a few days during ERT. The teachers shared reports of more individualised noticing for some students in the online environment, which may have been due to the lack of social interactions during online learning. With teachers being able to notice their students more on an individual level in ERT, they were able to spend more time with those who were willing, challenge some students who were looking for further extension, and providing extra assistance for those that required it.