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callbackfmt: Available with V‑Cloud 1.6+

Description: The callbackfmt parameter enables the selection of a specific callback format.

Values: multi (default), single, put


This is the default value. Setting callbackfmt to multi performs a multi-part POST to the callback with two parts specifying the request ID and the result file content.


Setting callbackfmt to single performs a standard POST that only contains the result file content within the POST body.

The request ID is retrievable through the POST's X-Request-ID header.


Identical to the callbackfmt=single except the callback is performed using an HTTP PUT instead of a POST.

Allows you to pass pre-signed AWS S3 URLs through the callback parameter to automatically upload the result to AWS S3.


All callback formats include the X-Request-ID header within their response.

The following command is a V‑Cloud API call using the callbackfmt parameter:

curl -F token=token \
     -F file=@sample.wav \
     -F callback=>http://sample.com:5555 \
     -F callbackfmt=single\

callbackerror: Available with V‑Cloud 1.6+

Description: Use callbackerror to specify a callback URL to receive results of erroneous jobs. If callbackerror isn't specified, erroneous job results are sent to the URL defined in the callback parameter.

Values: URL

The following command is a V‑Cloud API call using the callbackerror parameter:

curl -F token=token \
     -F file=@sample.wav \
     -F callback=http://sample.com:5555 \
     -F callbackerror=http://callbackerrorurl.com:5555 \