The bulk of Domesday Book has a regular structure, being divided into counties, boroughs, fiefs, Hundreds, vills, and manors. These structures are all encoded in the text. In addition, the Domesday Inquest was organised by circuits. Although the word itself does not appear in Domesday, and the structure of Domesday Book does not reflect the circuits employed by the Inquest proceedings, the nature and format of the data collected by the Domesday commissioners varied significantly from circuit to circuit. For this reason, Domesday Explorer allows searching to be limited to particular counties and circuits.
The personal names and status of all landholders are also coded. Personal names are always coded; institutional names are coded if they have tenurial significance. Where a landholder is mentioned more than once in a single entry in the same landholding context, the appropriate code is used only on the first occurrence of the name. If, however, a name appears several times in an entry in different landholding contexts, then the appropriate code is employed on each occasion.
Places are also coded to indicate their status in the hierarchy of manorial structures. The status of a holding is coded even when its name has been omitted. Holdings are also coded as to whether they are the subject of an entry or a dependency within an entry.
Finally, the individual components of each entry are coded: assessments to taxation and military service, the arable and plough teams on the estate, the manorial population, manorial appurtenances, and valuations. Each of these categories is separately coded, making it possible to restrict searches to those features of manors.