Inspectors

Fiddler's Inspectors display the request and the response for the selected session in the Live Traffic list. The inspectors are located in the right panel with the Request inspectors above the Response inspectors.

Select a session (from the Live Traffic list) to load its data into the Inspector's section. Request inspectors are shown at the top and Response inspectors are shown at the bottom (on the right panel)

Inspectors for Traffic Monitoring

The Inspectors allow you to view the content of each session's request and response in a variety of different formats. Fiddler supports multiple inspector types for the sessions' request (at the top) and response (at the bottom). Click on the desired Inspector's name (for example, Image or Raw) to switch the loaded Inspector.

Inspector types

Headers Inspector

The Headers Inspector allows you to view the HTTP headers of the request and the response. Headers Inspector

There are some conceptual differences between Request Headers and Response Headers, as listed below.

Request Headers

Every HTTP request begins with plaintext headers that describe what the client requests as a resource or operation. The first line of the request (the "Request line") contains three values: the HTTP method (for example GET), the URL path which is being requested (for example "/index.html"), and the HTTP version (for example "HTTP/1.2"). Request line can consist of one or more rows containing name-value pairs of metadata about the request and the client, such as the User-Agent and Accept-Language.

Response Header

Like the HTTP request, every HTTP response begins with plaintext headers that describe the result from the request. The first line of the response (the "Status line") contains the HTTP version (for example "HTTP/1.1"), the response status code (for example "200"), and the response status text (for instance "OK"). Following the Status line, are one or more lines containing name-value pairs of metadata about the response and the server, such as the length of the response file, the Content-Type, and how the response may be cached.

Text Inspector

The Text inspector allows you to view the request and response bodies as text. The Text Inspector truncates the data it shows at the first null byte it finds, making it an inappropriate choice for displaying binary content.

Most of the Inspector is a large text area that displays the body text interpreted using the character set detected using the headers, the byte-order-marker, or an embedded META tag declaration.

Text Inspector

Image Inspector

The Image Inspector (Response only) allows you to view the response bodies as an image. The Inspector can display most common web image formats, including JPEG, PNG, and GIF, as well as less common formats like cursors, WebP, JPEG-XR, bitmaps, TIFF. The Inspector does not support displaying SVG graphics (SVG responses can be viewed using the Web inspector).

Image Inspector

WebForms Inspector

The WebForms inspector (Request only) parses the request's query string and body for any HTML form-data. If a form is found, it is parsed, and the name/value pairs are displayed in the grid view. The Inspector works best with application/x-www-form-urlencoded data used by most simple web forms.

WebForms Inspector

Web Inspector

The Web Inspector (Response only) allows you to view responses in a web browser control, which provides a quick preview of how a given response may appear in a browser. The web browser control is configured to prevent additional downloads when rendering the response (to avoid flooding the Live Traffic list), meaning that most images and styles will not be displayed. Additionally, scripting and navigating are blocked, providing a read-only preview.

WebForms Inspector

Cookies Inspector

The Cookies inspector displays the contents of any outbound Cookie and Cookie2 request headers and any inbound Set-Cookie, Set-Cookie2 and P3P response headers.

Cookies Inspector

Raw Inspector

The Raw inspector allows you to view the complete request and response, including headers and bodies, as text.

Most of the Inspector is a large text area that displays the body text interpreted using the character set detected using the headers, the byte-order-marker, or an embedded META tag declaration.

Raw Inspector

JSON Inspector

The JSON Inspector interprets the selected request or response body as a JavaScript Object Notation (JSON) formatted string, showing a tree view of the JSON object's nodes. In case when the body can't be interpreted as JSON, the tree view will remain empty (as demonstrated for the request in the screenshot below). The JSON inspector can render the data even if the request/response is compressed or has HTTP chunked encoding applied.

The Inspector provides Expand All / Collapse All toggle button that will expand or collapse all nodes of the JSON tree.

JSON Inspector

If the JSON data is malformed (if, for instance, the name component of a name/value pair is unquoted), the JSON inspector will show a warning in the footer.

XML Inspector

The XML Inspector interprets the selected request or response body as an Extensible Markup Language (XML) document, showing a tree view of the XML document's nodes. If the body can't be interpreted as XML, the tree view will remain empty (as demonstrated for the request in the screenshot below). Each XML element is represented as a node in the tree. The attributes of the element are displayed in square brackets after the element's name.

XML Inspector

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