Sometimes an application makes a request a certain way, and while trying to mimic it, but executing a request from the REST endpoint, it doesn’t run the request quite the same as the application. However the existing request can be re-run in Fiddler with a modification.
Select the request in Fiddler. Right-click the request and click Replay > Reissue and Edit.
A new line appears for the reissued request. Make the modification necessary, such as in the web forms.
Choose Run to Completion.
Use Fiddler to send a request repeatedly, applying pressure to the service.
Capture a request using Fiddler.
Select the request, right-click, and click Replay > Reissue Requests (Or just click and type R).
Select multiple requests and do the same steps.
The same request can be run many times using this method.
Article ID: 000015143
Software: Portal for ArcGIS 10.3 (10.3.1), 10.4 (10.4.1) ArcGIS GIS Server 10.5 (10.5.1) Web AppBuilder for ArcGIS (Developer Edition) 1.x