The use of video, relating to teachers’ learning, is on the increase across the globe (Gaudin and Chalies, 2015). Video can allow the same example of teaching to be observed by many people, perhaps multiple times, and specific aspects of teaching and learning episodes to be focussed upon and discussed. It can allow access to a broader range of classroom contexts, mathematical content, and teaching approaches than otherwise might be available (Star & Strickland, 2008). Video can, more effectively than live observation, help teachers move from focussing on aspects of teaching and learning episodes that confirm their existing beliefs about ‘good’ teaching, towards attention to student learning and evidence thereof (Philipp et al., 2007). The role of the facilitator is crucial in realising the potential of video (Beswick & Muir, 2013).

The use of video in mathematics education has been the subject of significant research, making this Research Forum timely. We will not be considering methodological utilizations of video for broad research purposes. We are, rather, interested in the use of video with mathematics teachers for the purpose of enhancing teacher learning (within which we would include research using video, conducted by teachers). We note a trend in several parts of the world towards teachers supporting other teachers via using video. This trend can be seen, for instance, in Israel and in the USA, where teachers might be trained as mentors or facilitators of other teachers in the scaling up of research programmes (e.g. Beisiegel, 2016; Borko et al., 2017; Karsenty, 2016). It is therefore more important than ever to elaborate our understandings of how video can be used effectively in relation to teacher learning.

We have attempted a mapping of the terrain of work on video in relation to mathematics teacher learning and draw on specific projects (our own and others’) in order to exemplify trends and possibilities. This mapping takes the form of five dimensions of variation of video use with teachers of mathematics; elaborating these dimensions forms the bulk of this report. Before getting to these dimensions, we first look back over some past reviews of work on video in mathematics education and beyond in order to offer a sense of the state of the art as well as unresolved issues or questions.