In order to use the Betting API, you need to have an Application Key. The Application Key identifies your API client.  Two App Keys are assigned to a single Betfair account, one live App Key and one delayed App Key.

You must pass the Application Key with every HTTP request. You do this by setting the HTTP header with the value of the key assigned by Betfair.

X-Application: APP_KEY_ASSIGNED

You can create an Application Key for your Betfair account using the createDeveloperAppKeys operation or by using the Accounts API Visualiser. Please see the API Reference Guide for details of this operation.

Please note: the X-Application header is not required when using the createDeveloperAppKeys or the getDeveloperAppKeys service.

Delayed Application Keys

The createDeveloperAppKeys service will assign two Application Keys (App Keys) to your Betfair account.

One 'live' App Key and one 'delayed' App Key. A delayed App Key is displayed as 'Version 1.0-DELAY' via createDeveloperAppKeys/getDeveloperAppKeys

• The delayed App Key returns delayed price data and does not allow betting transactions to be performed (placeOrders,replaceOrders,updateOrders, cancelOrders)
• The delayed App Key should be used for development and any functional testing that doesn't require the use of live data and betting functionality. 
• The delayed App Key should also be used in simulation/practice applications where the facility to bet into live Betfair markets is not available.