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HTTP Callout Considerations and Limits
When using HTTP Callout, keep these considerations and limits in mind.
Required Editions
| Available in: Lightning Experience |
| View supported editions. |
Considerations
- JSON response with fields in a list that have the same data type is supported. For example, [1, 2, 3, 4] is a list of numbers with the same data type. But [“one”, 2, “three”, “four”] doesn’t have the same data type because 2 is a number, and the other values are strings.
- To ensure proper handling of empty responses from an HTTP callout, use an empty JSON
object
{}or an empty JSON array[]instead of an empty string"". - Enum data type isn’t supported. For example, if the API includes a Status field with finite values of Accepted and Rejected, the values don’t appear in Flow Builder as a multi-picklist. The Status field is instead inferred as a string data type and the callout response includes one value. See Enums.
- Float and long data types aren’t supported. If the API response provided during configuration includes a field with float or long data types, you can set the data type to integer or double.
- Include headers within the named credential when configuring the authentication, which supports global merged fields. Set headers on the URL endpoint for the callout rather than the invocable action.
- Request headers aren't supported. Instead, you can either set the headers as part of credentials or manually update the OpenAPI specification in the external service. This converts the HTTP Callout into a standard external service.
- When you call out to an external service action, a response status code of 300 or greater is returned as an error. Handle the error from an action by using a fault path. For example, you can get the error message from the fault path and show it to the user.
Limits
- Every time you create an HTTP callout action within Flow Builder, it auto-generates an external service registration. For more information, see Callouts and Callbacks: Limits and Usage.
- You can have up to 15 nested levels of fields and objects in a JSON hierarchy.
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