Before upgrading your environment to a newer version, it's recommended to test API calls against the new version. To do so, in the API request you can use a custom HTTP header specifying the API version you would like to use for that specific request. This allows you to stay on an older version and test your development environments against new versions.
fidel-version header allows you define in each request the version of the endpoint output. You can specify the current version or newer versions of the API.
Check the version log for more information about available versions.
Once your tests are complete you can upgrade your environment to a newer version under https://dashboard.fidel.uk/account.
curl -X GET \
-H 'content-type: application/json' \
-H 'fidel-key: sk_test_50ea90b6-2a3b-4a56-814d-1bc592ba4d63' \
-H 'fidel-version: 2019-03-05'