Power Platform Community Forum Thread Details

API request on Postman and SOAPUI works. On Power Automate fails , Using a Post Method ,authentication basic I have added the custom header with Authorization: Basic %Base64Credentials% and returns 401 whether the HTTP authenticate toggle is turned on (with credentials) and off.

Categories:

Power Automate Desktop

Hi,

This usually happens due to how authentication is handled in Power Automate vs Postman/SOAPUI.

A couple of quick things to check:

Don’t mix both authentication methods
If you are already passing:
Authorization: Basic %Base64Credentials%
then keep HTTP authentication toggle OFF. Using both can cause conflicts and lead to 401.
Verify Base64 encoding
Make sure your credentials are encoded as:
username:password → Base64
Also ensure there are no extra spaces or line breaks in the header.
Try using built-in authentication instead
Instead of custom header, turn ON HTTP authentication → Basic and provide username/password there, and remove the custom Authorization header.
Content-Type header
Add explicitly in headers if not already:
Content-Type: application/json
Encoding / request body
If the API is strict, try turning ON Encode request body or check if the API expects UTF-8 specifically.