Map Local Files

Remote mapping of a request location means testing changes or fixes locally and avoiding deploying on an actual remote host. However, testing against a localhost environment is often the more straightforward, quicker, and cheaper solution. Mapping HTTP requests can be done to remote locations and local sources like files, Fiddler's predefined responses, or manual responses (through the Fiddler user interface).

With Fiddler Everywhere, you can easily create a rule that maps HTTP requests to a local DAT file (which contains the modified HTTP response).

Creating a "Map Local (File)" Rule

Create a "Map Local (File)" rule by setting the following actions through the Rules Builder.

  1. Create a matching condition that uses the "When all these conditions are met any number of times" pattern.

  2. Match by a URL that uses a string value to match the desired URL. For example:

  3. (Optional) If you need to test a URL that your DNS server cannot resolve, create a Return CONNECT Tunnel action.

  4. Create a Return File action and set the path to the DAT file that contains the modified HTTP response. The DAT file must contain a well-formed HTTP response. For example:

    HTTP/2 200
    accept-ranges: bytes
    age: 339925
    cache-control: max-age=604800
    content-type: text/html; charset=UTF-8
    date: Fri, 05 Apr 2024 08:26:52 GMT
    etag: "3147526947"
    expires: Fri, 12 Apr 2024 08:26:52 GMT
    last-modified: Thu, 17 Oct 2019 07:18:26 GMT
    server: ECS (sed/58EA)
    vary: Accept-Encoding
    x-cache: HIT
    content-length: 1382
    <!doctype html>
        <title>Fiddler Everywhere - Example Domain</title>
        <meta charset="utf-8" />
        <meta http-equiv="Content-type" content="text/html; charset=utf-8" />
        <meta name="viewport" content="width=device-width, initial-scale=1" />
        <style type="text/css">
        body {
            background-color: #f0f0f2;
            margin: 0;
            padding: 0;
            font-family: -apple-system, system-ui, BlinkMacSystemFont, "Segoe UI", "Open Sans", "Helvetica Neue", Helvetica, Arial, sans-serif;
        h1 {
            color: white
        div {
            width: 600px;
            margin: 5em auto;
            padding: 2em;
            background-color: darkslategray;
            border-radius: 0.5em;
            box-shadow: 2px 3px 7px 2px rgba(0,0,0,0.02);
        a:link, a:visited {
            color: #38488f;
            text-decoration: none;
        @media (max-width: 700px) {
            div {
                margin: 0 auto;
                width: auto;
        <h1>Modified by Fiddler Everywhere</h1>
        <p>This domain is for use in illustrative examples in documents. You may use this
        domain in literature without prior coordination or asking for permission.</p>

This sample Fiddler rule maps an HTTP request to return a manually-crafted response.

Creating "Map Local (File)" rule

Instead of manually creating a DAT file that contains a proper response, you can use one of Fiddler's predefined DAT files available through the Return Predefined Response action.

Once the rule is created, enable the Rules tab, toggle the rule switch, and start capturing traffic.

Activating the "Map Local (File)" rule

Download a ready-to-use "Map Local (File)" rule as a FARX file, which you can import through the Rules toolbar.

See Also