UK universities are increasingly making decisions about undergraduate admissions with reference to various contextual indicators which are intended to identify whether or not an applicant comes from a disadvantaged family, neighbourhood or school environment. However, the indicators used are often chosen because they are readily available, without much consideration of the possible alternatives and their comparative quality. This paper is part of a larger scoping review of existing research literature used to compile a list of potential contextual indicators, and assess these with respect to their quality, availability, and their relationship to outcomes in UK higher education. A search was made of relevant electronic databases, yielding around 120,000 reports initially, and 28 categories of indicators. Each indicator was assessed on the basis of existing evidence concerning its relevance, reach, availability, accuracy, reliability, and completeness – and in terms of whether its use might inadvertently create a different kind of injustice or lower the student outcomes for HEIs. Many possible indicators are not readily available, or not accurate enough for use in policy and practice. In general, indicators concerning individual circumstances are more relevant than area-based or school characteristics. As expected, there is no ideal single indicator. And it is not clear that combining indicators leads to the advantages rather than the deficits of all. Here we list the best available. There are some indicators for very small categories that can be used relatively un-problematically as long as the data can be made available at time of candidate selection, and these include being a recent refugee or asylum-seeker and having spent time living in care. However, neither of these is a solution to the more general issue of contextualised admissions. School type attended (private or state-funded) could also be used relatively safely, but requires clear definition, could lead to inadvertent injustice, and might not be necessary if good individual data on relative advantage is available instead. The category of mature applicant is also relatively unproblematic, but it is not clear that simply being older than traditional age is a disadvantage. The two most general indicators, most suitable for use, are considered to be eligibility for (or receipt of) free school meals, and having a disability or special educational need. However, like school type, both need care and some adjustment from how they are currently used or recorded. FSM should be based on a more refined measure than the usual yes/no threshold – and based on our secondary analyses reported elsewhere we propose the number of years an applicant has been known to be FSM-eligible. The range of recorded disabilities is now so great that again a simple yes/no flag is not appropriate. Instead, we will conduct more detailed work on how to use the disaggregated sub-categories in the most appropriate manner.