Use this page to geocode a large number of UK postcodes. Paste them into the 'Addresses' box (each address separated by a new line), choose your options and hit the 'Geocode' button. Then go and make a cup of tea and when you return the 'Output' box should have comma separated geocoded addresses, in latitude/longitude and easting/northing (if you've chosen the UK option).
Due to a massive increase in Google Maps costs, this page only currently supports UK postcodes. Sorry.
Supported colours are red, green, blue, yellow, black, white, pink, orange, grey, brown
Why does it slow down after a few hundred addresses?
The site uses Google Maps for geocoding. Their service has a limit on the number of requests it will process. I try to mitigate this by increasing the time between requests but this means geocoding gets slower and slower. There is a workaround that seems to alleviate the issue. Process addresses in batches of a few hundred and refresh the page between each batch. Note, if you're geocoding UK postcodes you shouldn't experience the slowdown since that uses my own database.
What is the meaning of the result quality?
Addresses geocoded with Google Maps provide the following result quality information.
Rooftop indicates that the returned result is a precise geocode for which we have location information accurate down to street address precision. (most accurate)
Range interpolated indicates that the returned result reflects an approximation (usually on a road) interpolated between two precise points (such as intersections). Interpolated results are generally returned when rooftop geocodes are unavailable for a street address.
Geometric centre indicates that the returned result is the geometric center of a result such as a polyline (for example, a street) or polygon (region).
Approximate indicates that the returned result is approximate. (least accurate)