Where the data comes from
Nothing here is typed in by hand. Each record is assembled from a published government source and rebuilt on a schedule, so the atlas reflects what those sources said on the date shown against each establishment.
- GOV.UK Search and Content APIs
- The list of establishments, their addresses, phone numbers, category and operator. Every prison, YOI and IRC has a published guidance page; the atlas reads those pages directly rather than a hand-kept list, so a new or renamed establishment appears on the next run.
- Refresh: Daily · Open Government Licence v3.0
- postcodes.io
- Coordinates. Addresses from GOV.UK carry a postcode but no latitude or longitude, so postcodes are resolved in bulk against ONS and Ordnance Survey open data.
- Refresh: Daily, for anything not yet located · Open Government Licence v3.0
- Ministry of Justice population and capacity tables
- Numbers held, certified normal accommodation and operational capacity. Each run stores a dated snapshot, so occupancy can be read as a trend rather than a single figure.
- Refresh: Monthly release, checked daily · Open Government Licence v3.0
- HM Inspectorate of Prisons
- Published inspection reports, matched to an establishment by name.
- Refresh: Daily · Open Government Licence v3.0
- HMPPS announcements on GOV.UK
- News and publications that name a specific establishment. National items are discarded.
- Refresh: Daily · Open Government Licence v3.0
Reading the figures
Certified normal accommodation is the population an establishment can hold without crowding. Operational capacity is the most it can safely hold. Occupancy on this site is population against certified normal accommodation, so a figure above 100% means people are being held in crowded conditions, which is a routine and lawful state for much of the estate rather than an exception.
Reuse
The whole dataset is available as JSON at /api/prisons and as GeoJSON at /api/prisons?format=geojson. It contains public sector information licensed under the Open Government Licence v3.0. Basemap tiles are © CARTO, map data © OpenStreetMap contributors.
Corrections
If a record is wrong, it is almost always wrong upstream or mismatched during a name lookup. The feed status page shows what each run read and what it could not place.