Alternatively a small white square appears superimposed over a section of a thumbnail of the whole image, with the highlighted section relating to the detail being viewed in the main body of the image. Visitors can drag this square round the thumbnail or touch another section in the thumbnail to view a different detail. The most well known portraits have captions that have been specifically written by Curators at the National Portrait Gallery about that portrait. In addition to the Gallery written biographies about sitters and artists, there are more detailed biographies on nearly 4,000 of the 8,300 different sitters and artists presently represented on the Portrait Explorer . These have been reproduced from The Concise Dictionary of National Biography, with the kind permission of Oxford University Press.
Some portraits have additional tabs which allow visitors to explore other aspects of interest.
Companion portraits can be seen side by side. Other tabs allow visitors to see the front and back of medals, preparatory studies or sketches for a final portrait or link to other related portraits. The Gallery has made available to the public hundreds of archival documents not normally on display to the public. These are in the main letters from sitters or artists or their descendants to the Gallery that provide visitors with a different insight into the portrait being viewed. Who's who in a portrait Visitors are able to identify who is who in over 300 group portraits by touching the head of a sitter or the name of any sitter listed underneath the image of the portrait.