How to evaluate any UK address for free using open data APIs

1. Postcode to coordinates — postcodes.io

postcodes.io is a free ONS-derived API returning latitude, longitude, local authority, ward, LSOA, region and constituency for a UK postcode. Almost every other lookup here needs coordinates, so this is where a pipeline starts.

2. Energy performance — MHCLG EPC API

Get energy performance of buildings data provides certificates by postcode or address, including total floor area, ratings, heating, construction age band and recommendations. It requires free registration and an API key, and responses are per-certificate — matching a certificate to a specific address is the hard part, not fetching it.

3. Sold prices — HM Land Registry

landregistry.data.gov.uk exposes Price Paid data through linked-data REST and SPARQL endpoints. Query by postcode and sort by transaction date. No key required. Remember the registration lag and the England-and-Wales-only coverage.

4. Planning designations — planning.data.gov.uk

planning.data.gov.uk publishes national planning datasets — conservation areas, listed buildings, flood zones, article 4 directions, green belt — queryable by point geometry. It does not contain individual planning applications; those stay with the local authority.

5. Flood — Environment Agency

The flood-monitoring API returns flood areas near a coordinate and any warnings currently in force. For long-term modelled risk, direct users to the public service rather than trying to derive it.

6. Crime — Police.uk

data.police.uk publishes street-level crime by month and category around a coordinate. Locations are snapped to anonymised points, so treat them as area context and never as street-accurate.

Others worth knowing

• Ordnance Survey Data Hub — addressing and mapping APIs, free tier available.
• UK House Price Index — mix-adjusted price movement by local authority.
• British Geological Survey — ground stability and radon context.
• Companies House API — for corporate freeholders and management companies.

The part that is genuinely hard

Fetching is easy. Matching is not. Address strings differ between every register: "Flat 2, 14 Example Road" in one, "14A EXAMPLE RD" in another. Deciding whether a certificate belongs to the property you care about — and being honest when you cannot tell — is where the real work lives. That is why FirstBid grades every match as high confidence, limited confidence, not verified, or no record found, and refuses to let anything below high confidence move a financial figure. Our methodology page sets out how.