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postcodes.io · Ordnance Survey open data

UK postcode lookup

Validate a UK postcode against postcodes.io open data derived from Ordnance Survey Code-Point Open. Confirm country or region when needed, then anchor the Affix yes or no with Merkle proof.

PostcodeOpen data
CountryOptional check
MerkleAudit leaf

Live check

Run postcodes check

Source: postcodes.io. Every search attaches a fresh Affix Merkle proof.

Full UK postcode, spacing optional.

Leave blank to only check that the postcode resolves.

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Questions

Which dataset powers this?

postcodes.io serves open UK postcode data including Code-Point Open derived fields.

What if the postcode is wrong?

Unresolved postcodes return no with a Merkle proof of the negative decision.

Can I require England only?

Yes. Set expected country to England. A Scottish postcode then returns country_mismatch.