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We have been investigating issues with the API where the response time intermittently increases by several orders of magnitude.

Our assessment is that a significant cause of this is requests using the HTTP header “Expect: 100-continue”. 

From the 27th July we are making a change to the Betfair API so that it responds to the HTTP header “Expect: 100-continue” with an HTTP1.1 compliant response of "417 Expectation Failed”. 

Therefore, you will need to update your application to ensure that you are no longer sending this header with API requests to prevent the error response from being returned.

Advice for developers

.NET - we are aware that this header is sent by default and can be disabled by setting System.Net.ServicePointManager.Expect100Continue = false;

Java – this parameter isn’t sent by default but can be removed via the parameter CoreProtocolPNames.USE_EXPECT_CONTINUE

Please let us know if you have any questions regarding this

Betfair Developer Program