Http request to send base64 image string in POST methos

I have to call api request to send a. Png file. I am able to convert it to base64 string. But when I am trying to make POST call it is giving error. I am sending the string as paramter to the request.

Error:Input should be a valid dictionary or object to extract fields.

Need suggestion to resolve it.

Hi!

Could you supply us with a screenshot of the properties of your http request?

Have you tried testing the API via postman?
Usually the Base64 encoded string would be part of the body of the request, but it depends on the specific API how it’s realised, do you have the documentation for the API you’re trying to use?