---
title: "Using Fiddler with Decisions"
slug: "using-fiddler-with-decisions"
description: "Learn how to configure Fiddler to capture and analyze Decisions API calls, including request headers and request details."
updated: 2026-04-27T20:46:34Z
published: 2026-04-28T14:12:55Z
canonical: "documentation.decisions.com/using-fiddler-with-decisions"
---

> ## Documentation Index
> Fetch the complete documentation index at: https://documentation.decisions.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Using Fiddler with Decisions

## Overview

[Fiddler](https://www.telerik.com/fiddler/fiddler-classic) is a comprehensive web debugging and analysis tool. For Decisions, Fiddler can be used to assist with debugging API calls by providing access to the request headers/details. This article will cover the necessary changes needed to utilize Fiddler.

## Configuring Fiddler in Decisions

Fiddler cannot capture traffic from localhost; therefore, the following needs to be configured for Decisions.

1. Open **DecisionsServiceHost.exe.config** with a text editor. This file can be found under **C:\Program Files\Decisions\Decisions Services Manage**r for a standard install.![](https://cdn.document360.io/6ef8bcc1-6489-4486-9ad1-83acff7e5df0/Images/Documentation/2022-01-20_15h09_47(1).png)
2. Once opened, the following needs to be added within the **AssemblyBinding** block within the file:

```markup
<system.net>
<defaultProxy
                enabled = "true"
                useDefaultCredentials = "true">
<proxy autoDetect="false" bypassonlocal="false" proxyaddress="http://127.0.0.1:8888" usesystemdefault="false" />
</defaultProxy>
</system.net>
```

Once the following lines have been added, [Restart Decisions](https://documentation.decisions.com/version-10/docs/restart-decisions-application).