The Composer tab enables you to manually build and send HTTP, HTTPS, and FTP requests.
The Composer contains three major sections used to construct a request and observe the response.
The bottom section is a response inspector, which shows the response from the executed request.
Fiddler's Composer is adding by default its
User-Agentso that it sends HTTPS request correctly. You could remove the default
User-Agentheader but notice that this could break composing a secure request (HTTPS). The default key-value
The Composer supports creating a request while using one of the following HTTP methods:
- GET - Requests a representation of the specified resource. Requests using GET should only retrieve data.
- PUT - replaces all current representations of the target resource with the request payload.
- POST - Used to submit an entity to the specified resource, often causing a change in state or side effects on the server.
- DELETE - Deletes the specified resource.
- HEAD - Asks for a response identical to a GET request, but without the response body.
- TRACE - Performs a message loop-back test along the path to the target resource.
- SEARCH - Used by a client to ask the server to perform a query operation (described by the request payload) over some set of data scoped to the effective request URI.
- PROPFIND - Retrieves properties defined on the resource identified by the Request-URI.
- PATCH - Used to apply partial modifications to a resource.
- MKCOL - The method may be included in the scope of a transaction by submitting a Transaction Header with a lock token that corresponds to that transaction.
- MOVE - Used to move a resource to the location specified by a request Uniform Resource Identifier (URI
- LOCK - Used to take out a lock of any access type on a resource so that another principal will not modify the resource while it is being edited.
- UNLOCK - Used to remove the lock on the resource at the request Uniform Resource Identifier (URI).
- OPTIONS - Used to describe the communication options for the target resource.
The URL field is the place to endpoint URL for the composed request.
From the HTTP Version drop-down, you can select the following HTTP versions:
- HTTP 2.0
- HTTP 1.2
- HTTP 1.1
- HTTP 1.0
- HTTP 0.9
The Headers, Params and Body section is allowing you to further modify your request by adding your custom Headers, Params, Body, and observing the composed request via the Raw view.
Enables you to add/modify your request headers (e.g.,
Add a new header by entering the header key-value pair and then clicking the tick.
Adds the new header to your request. The header can now be disabled/enabled or completely deleted.
Most of the servers using newer versions of TLS will require a User-Agent header to be set. By default, Fiddler Everywhere will a User-Agent key set with value Fiddler Everywhere and description Lets servers and network peers identify the application, operating system, vendor, and version of the requesting user agent. The header is non-mandatory, but keep in mind that without valid User-Agent, some requests to secure servers might fail.
Enables you to add query parameters to your request URL easily. Adds any key-value pair appended through the Params view to the request URL.
Add new query params by entering the params key-value pair and then clicking the tick.
Add the new query params to your request URL. The params can be disabled/enabled or completely deleted.
Enables you to manually specify the data that should be sent with the request.
The view is a raw representation of the composed request. This view is non-editable.
With the Response Inspector, you can inspect the received response (from the executed request). The inspector provides several views to visualize different parts of the request in specific formats. Find detailed information on each inspector type in the dedicated article about Inspector Types
A session previosly captured in the Live Traffic could be loaded in the Composer for applying further modifications.
Select the desired session and make a right-click to open the context menu. From the context menu, select Edit in Composer. Alternatively, select the session and use the keyboard shortcut by pressing key E.
The session opens in a new Composer window and then you could change the desired values. For example, change the data payload, modify the headers, test the authentication, etc.