# Fiddler CLI Command Reference This article lists the built-in commands of the [Fiddler CLI](https://www.telerik.com/fiddler/fiddler-everywhere/documentation/command-line/fiddler-cli) and shows how to use them. Commands are case-insensitive. Arguments are positional—pass values directly after the command name, without option names. ## Commands | Command | Description | Example | | :------------------------------------ | :------------------------------------------------------------------------------------------------------------------------ | :------------------------------------------------------- | | `start` | Starts capturing traffic through the system proxy. | `fiddler-cli start` | | `stop` | Stops capturing traffic through the system proxy. | `fiddler-cli stop` | | `status` | Shows the application and proxy status. | `fiddler-cli status` | | `show` | Shows and focuses the Fiddler Everywhere main window. | `fiddler-cli show` | | `hide` | Hides the Fiddler Everywhere main window. | `fiddler-cli hide` | | `clear` or `cls` | Deletes the completed live sessions and keeps the active (still running) sessions. | `fiddler-cli clear` | | `dump [directory]` | Exports the live sessions to a SAZ file, and then clears them. Saves the file to the Desktop when you omit the directory. | `fiddler-cli dump ./captures` | | `bpu [text]` | Breaks before requests whose URL contains the text. Omit the text to clear the breakpoint. | `fiddler-cli bpu example.com/api` | | `bpv [method]` or `bpm [method]` | Breaks before requests with the specified HTTP method. Omit the method to clear the breakpoint. | `fiddler-cli bpm POST` | | `bps [status]` | Breaks before responses with the specified HTTP status code (`100`–`599`). Omit the status to clear the breakpoint. | `fiddler-cli bps 500` | | `bpafter [text]` or `bpa [text]` | Breaks before responses whose request URL contains the text. Omit the text to clear the breakpoint. | `fiddler-cli bpa example.com/api` | | `g` or `go` | Resumes all sessions paused at breakpoints. | `fiddler-cli go` | | `urlreplace ` | Adds a temporary URL replacement. Run without values to clear it. | `fiddler-cli urlreplace example.com staging.example.com` | | `overridehost ` | Adds a temporary host mapping. Run without values to clear all host mappings added through the CLI. | `fiddler-cli overridehost example.com 127.0.0.1:8080` | | `help`, `--help`, `-h`, or no command | Lists the available commands. | `fiddler-cli help` | Any other command name is forwarded to the `OnCliCommand` handler of the active script. For details, see [Custom CLI Commands](https://www.telerik.com/fiddler/fiddler-everywhere/documentation/scripting/script-custom-cli-commands). ## Capture and Application Commands ### start and stop The `start` command enables the Fiddler Everywhere system proxy and starts capturing traffic. The `stop` command disables the system proxy. ```sh fiddler-cli start ``` ```txt Proxy enabled. ``` If the proxy is already in the requested state, the CLI reports `Proxy is already enabled.` or `Proxy is already disabled.`. If Fiddler Everywhere cannot change the proxy state, the command fails with the `proxy_unavailable` error. ### status The `status` command reports the sign-in, proxy, and scripting state of Fiddler Everywhere. It doesn't require a signed-in user. ```sh fiddler-cli status ``` The output contains the following values (`True` or `False`): | Value | Description | | :----------------- | :-------------------------------------------------------------------------------- | | `userSignedIn` | The user information is loaded and a user profile exists (the user is signed in). | | `proxyEnabled` | System traffic capturing is enabled. | | `scriptingEnabled` | Scripting is switched on and at least one script is marked as enabled. | ### show and hide The `show` command shows and focuses the Fiddler Everywhere main window. The `hide` command hides it. Use `show` after starting Fiddler Everywhere with the `--hidden` option. ```sh fiddler-cli --hidden start fiddler-cli show ``` ## Session Commands ### clear and cls The `clear` command (or its alias `cls`) deletes the completed sessions from the **Live Traffic** list. Sessions that are still in progress are kept. After the command completes, Fiddler Everywhere also clears the session selection in the **Live Traffic** list. ```sh fiddler-cli clear ``` ```txt Cleared 42 completed live session(s); active sessions were kept. ``` ### dump The `dump` command exports the live sessions to a SAZ file and then clears the exported sessions. The CLI creates a uniquely named file, for example, `fiddler-cli-dump-20250101-093000123-.saz`, so running the command repeatedly never overwrites previous exports. * When you omit the directory, the CLI saves the file to your Desktop. * A relative directory is resolved from the current working directory of the terminal. * The directory must already exist. Otherwise, the command fails with the `invalid_arguments` error. * Fiddler Everywhere clears the exported sessions only after the export succeeds. If the export fails, the sessions remain in the **Live Traffic** list. The command prints the full path to the created file: ```txt Live sessions exported to '/Users//Desktop/fiddler-cli-dump-20250101-093000123-....saz' and cleared. path: /Users//Desktop/fiddler-cli-dump-20250101-093000123-....saz ``` If there are no live sessions, the CLI prints `No live sessions to dump.`. The following examples export the sessions to a specific directory: ```powershell # Windows PowerShell fiddler-cli dump C:\captures fiddler-cli dump "$env:USERPROFILE\My Captures" fiddler-cli dump .\captures ``` ```bat :: Windows Command Prompt fiddler-cli dump C:\captures fiddler-cli dump "%USERPROFILE%\My Captures" fiddler-cli dump .\captures ``` ```sh # macOS and Linux fiddler-cli dump ~/captures fiddler-cli dump "$HOME/My Captures" fiddler-cli dump ./captures ``` You can open the exported SAZ files in Fiddler Everywhere. For more information, see [Exporting and Importing Sessions](https://www.telerik.com/fiddler/fiddler-everywhere/documentation/collaboration/exporting-and-importing). > tip Only one `clear`, `cls`, or `dump` command can run at a time. If you run another one while the previous command is still in progress, the CLI reports the `operation_in_progress` error. ## Breakpoint Commands Breakpoint commands pause matching sessions so that you can inspect and modify them in Fiddler Everywhere before they continue. For more information about breakpoints, see [Breakpoints](https://www.telerik.com/fiddler/fiddler-everywhere/documentation/modify-and-filter-traffic/breakpoints). | Command | Pauses | Matches when | | :------------------------------- | :------------------------------------------------ | :-------------------------------------------------------- | | `bpu ` | Requests, before they are sent to the server | The request URL contains the text. | | `bpv ` or `bpm ` | Requests, before they are sent to the server | The request method equals the value, for example, `POST`. | | `bps ` | Responses, before they are returned to the client | The response status code equals the value. | | `bpafter ` or `bpa ` | Responses, before they are returned to the client | The request URL contains the text. | Each breakpoint command holds a single value. Running the command again with a new value replaces the previous one. Running the command without a value clears that breakpoint. For example: ```sh fiddler-cli bpu example.com/api # Break on requests to example.com/api fiddler-cli bpu example.com/auth # Replace the URL condition fiddler-cli bpu # Clear the URL breakpoint ``` The text and method values that you pass to the breakpoint commands are **case-sensitive**. For example, `fiddler-cli bpu /API/` doesn't match the `/api/` URLs, and `fiddler-cli bpm POST` doesn't match requests that use a lowercase method value. The `g` command (or its alias `go`) resumes all sessions that are currently paused at a breakpoint: ```txt Resumed 3 paused session(s). ``` ### Example: Debugging an API Call The following flow pauses the responses of failing API calls, lets you inspect them, and then cleans up: 1. Start capturing and set a response breakpoint for server errors: ```sh fiddler-cli start fiddler-cli bps 500 ``` 2. Reproduce the problem in your application. Fiddler Everywhere pauses each response with status code `500` so that you can inspect or modify it in the **Live Traffic** list. 3. Resume the paused sessions: ```sh fiddler-cli go ``` 4. Clear the breakpoint and export the captured sessions for later analysis: ```sh fiddler-cli bps fiddler-cli dump ``` ## Temporary Rule Commands The `urlreplace` and `overridehost` commands create temporary rules that modify the captured traffic. The temporary rules and the breakpoints that you set through the CLI behave as follows: * They are stored in memory and are lost when you close Fiddler Everywhere. * They apply even when the **Rules** switch in the **Rules** tab is off. * They are evaluated before the rules defined in the **Rules** tab and take priority over them. * They don't appear in, and don't change, the rules saved in the **Rules** tab. ### urlreplace The `urlreplace ` command replaces the `find` text with the `replace` text in the URL of each future request that contains `find`. The match is case-sensitive. ```sh # Send production API calls to a staging server fiddler-cli urlreplace api.example.com api.staging.example.com ``` The CLI holds a single URL replacement. Running the command with new values replaces the previous replacement. To remove the text from URLs, pass an empty string as the replacement value: ```sh fiddler-cli urlreplace "/v2/" "" ``` To clear the URL replacement, run the command without values: ```sh fiddler-cli urlreplace ``` ### overridehost The `overridehost ` command routes the requests for `host` to `target`. Both values must be a hostname, an IP address, or a `host:port` pair. ```sh # Route example.com to a local development server fiddler-cli overridehost example.com localhost:5000 ``` Unlike `urlreplace`, you can add multiple host overrides—each call adds a new mapping. For HTTPS requests, Fiddler Everywhere ignores the certificate name mismatch that the redirection causes. To clear all host overrides added through the CLI, run the command without values: ```sh fiddler-cli overridehost ``` ```txt Cleared 2 Fiddler CLI host override(s). ``` ## See Also * [Fiddler CLI](https://www.telerik.com/fiddler/fiddler-everywhere/documentation/command-line/fiddler-cli) * [Custom CLI Commands](https://www.telerik.com/fiddler/fiddler-everywhere/documentation/scripting/script-custom-cli-commands) * [Modifying Traffic with Rules](https://www.telerik.com/fiddler/fiddler-everywhere/documentation/modify-and-filter-traffic/modify-traffic-with-rules) * [Exporting and Importing Sessions](https://www.telerik.com/fiddler/fiddler-everywhere/documentation/collaboration/exporting-and-importing)