All documents in Dimensions are categorised according to standard classification systems, where there is enough information to do so. These systems include the "Fields of Research" (in all Dimensions versions) as well as RCDC, HRCS and Cancer-specific CSO/CT codes (subscription versions of Dimensions only).
In addition to this, "Coding support" and the Dimensions API can be used to automatically categorise any text which is pasted in, according to the same categorisation systems (these features are available in subscription only).
When using the API or "Coding support" to classify documents, you may sometimes find that the same document will have different categories assigned to it from what is listed in Dimensions (if the document is already indexed in Dimensions). This happens because pre-computed document classifications often derive from multiple data enrichment steps aimed at improving the category precision e.g. by looking at the overall topic area for a journal. As these enrichment steps are not carried out in the API or Coding support classifications, differences can arise despite both these and Dimensions using the same classification algorithms.