---
title: "DNS Resolver Override"
slug: "dns-resolver-override"
updated: 2025-07-14T16:22:54Z
published: 2025-07-14T16:22:54Z
canonical: "docs.catchpoint.com/dns-resolver-override"
---

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

# DNS Resolver Override

## Overview

The DNS Resolver Override feature allows you to specify a custom DNS server instead of using the default resolver provided by the operating system. This is useful for a variety of use cases, such as:

Comparing the performance of public DNS resolvers like Google (8.8.8.8) and OpenDNS.

Validating DNS-based geo-balancing or geo-targeting configurations.

## Implementation

You can configure DNS Resolver Override in two ways:

### Via HTTP Request Header
Navigate to the HTTP Request Header section under the Request tab. Here, you can add a custom DNS resolver using the DNS-Resolver-Override header.

### Via Transaction Script using setHeader()
This method is available for API (JavaScript) monitors. Here's an example of how to set it:

~~~
// Step - 1
setHeader("DNS-Resolver-Override", "8.8.8.8")
open("https://www.URL.com")
~~~

### For Object Monitors
When configuring an Object test, you can apply the DNS override directly in the **Request** settings by adding a custom HTTP header.

**Note: this option forces the agent to not cache the DNS response locally on the operating system. This ensures that there is no cross-test pollution of DNS records which might cause geo-targeting problems for certain companies.**