We don't provide a separate sandbox environment, but free trial accounts are available with 100 free lookups for testing.
Signing up for a trial account with us gives full access to the data for a limited number of requests. There is no commitment and no credit card is required, you only pay if you decide to use our service on a live system.
Once your trial period is finished and you convert to a live, paid for account, we also have some free postcodes you can test with:
UK Postcode Lookup API - the free test postcodes are AA1 1AA, AA1 1AB, AA1 1AD and AA1 1AE. They represent fictitious data.
Auto-Complete API - you can test for free with our own real postcode SL6 7RJ. The data is real and has a mix of residential and commercial addresses.