SO21 postcode district

Postcodes and sectors

743 of the district's 936 postcodes are live in the ONS Postcode Directory of August 2026. A postcode directory says whether a code is in use, never who is there. The live postcodes centre on 51.07521, -1.31660, which locates the district, not a building.

Companies registered in SO21

Companies House lists 2,025 companies with a registered office in SO21; 38 of them at addresses shared by 25 or more companies (1 October 2026 snapshot). 25 is the count at which the address lookup reports a company cluster.

Places OS Open Names lists for SO21

• Hampshire
• South East
• Winchester
• Colden Common
• Twyford
• South Wonston
• Test Valley
• Sutton Scotney
• Otterbourne
• Barton Stacey
• Itchen Abbas
• Sparsholt
• Compton
• Hursley
• Crawley
• Easton
• Worthy Down
• Owslebury
• Eastleigh
• Micheldever
• South Down
• Basingstoke and Deane
• Martyr Worthy
• Westley

Roads filed under SO21

Named roads first, then numbered ones. A road is filed under one district even where it runs through several, so a street missing here may be listed under a neighbouring district — which is why the address lookup never calls a British street absent. Great Britain has no open register of buildings, so a listed road never means a building on it exists.

• Alder Close
• Alexandria Road
• Alresford Drove
• Alresford Road
• Anders Road
• Andover Road
• Armstrong Close
• Ash Close
• Ashfields
• Aspen Close
• Attwoods Drove
• Badgers Bolt
• Baring Close
• Barron Close
• Barton Drove
• Basingstoke Road
• Baybridge Lane
• Beechcroft
• Beech End
• Beech Grove
• Beggars Drove
• Belmore Lane
• Berry Lane
• Bertune Close
• Birch Close
• Bishopstoke Lane
• Black Horse Mews
• Blackthorn Close
• Blackthorn Green
• Blackwell Road
• Bluebell Green
• Borman Way
• Bostock Close
• Bourne Close
• Bourne Fields
• Bourne Lane
• Boyes Lane
• Brambles Close
• Brambridge
• Brewers Lane
• Brickmakers Road
• Bridge Lane
• Bridgetts Lane
• Brooklyn Close
• Brooks Way
• Brunel Close
• Buddlesgate
• Bullington Lane
• Bunstead Lane
• Burne Close
• Burns Close
• Burr Close
• Burrow Road
• Callowing Close
• Carmans Lane
• Carthagena
• Castle Lane
• Chalk Dell
• Chapel Avenue
• Chapel Grove

Check an address in SO21

Check an address in SO21

The same road list through the API, from the outward code alone:

curl "https://spaw.co/api/v1/address/streets?country=GB&postal_code=SO21" \
  -H "Authorization: Bearer $SPAW_KEY"

Common questions about SO21

What does an SO21 postcode tell you?

That the address lies in the SO21 district of the SO (Southampton) postcode area, and the place OS Open Names most often lists first for its postcodes is Winchester. The district alone does not place a street: the inward half of the full postcode narrows the address to one of the district's 743 live postcodes.

Where the counts come from

• ons-postcode-directory · version 2026-08 · Contains ONS, OS and Royal Mail data © Crown copyright and database right 2026, Open Government Licence v3.0. Northern Ireland postcodes are excluded: their reuse needs a Land & Property Services licence.
• os-open-names · version 2026-11-01 · Contains OS data © Crown copyright and database right 2026, Open Government Licence v3.0.
• uk-companies-house · version 2026-10-01 · Companies House free company data product, Open Government Licence v3.0

What each figure means, and what a district page never says, is set out in Reading a British postcode district page; the glossary defines a postcode district, a postcode area, a postcode directory and a street register.

Data synced on 2026-11-01: the newest version among the datasets listed above.

Districts nearest SO21

• SO230.9 km
• SO221.6 km
• SO5311.0 km
• SO2411.9 km
• SO5011.9 km
• SO5214.1 km
• SO2014.7 km
• SO5115.8 km
• SO3216.0 km
• SO1817.1 km
• SO1717.3 km
• SO1617.4 km
• Every district
• How a British address is written
• Check any address

distance between the districts' centroids