Professional

Custom actions

• Last updated: March 31, 2025

• Read time: 3 Minutes

Custom actions are tasks that you can apply to HTTP messages in Burp Repeater to extract, transform, and analyze data.

Custom actions are powered by Bambdas, which are snippets of code that run directly from Burp Suite's interface.

You can use custom actions to:

• Analyze responses - Extract data, count elements, decode and encode message content, and check for specific content.

• Retrieve additional data - Perform lookups, resolve hostnames, and fetch external data.

• Resend requests - Modify headers, parameters, or body content and resend the request.

Adding custom actions

You can add Bambdas to the Custom actions side panel in Repeater in the following ways:

• Load existing Bambdas - Load Bambdas from your Bambda library. To start populating your library, you can download and import Bambdas from our GitHub repository. For more information, see Importing Bambdas.

• Create new Bambdas - Write your own custom action Bambdas.

• Add sample Bambdas - If the Custom actions panel is empty, click Add samples to load a set of example Bambdas that you can try out.

Loading Bambdas from your library

You can load previously saved Bambdas from your Bambda library into the Custom actions side panel.

To load a Bambda from your library:

1. In Repeater, click Custom actions to open the Custom actions side panel.

2. Click Load.

3. Select a recent Bambda from the list.

4. If the Bambda you want to load isn't in the list, click View all to view all Bambdas stored in your library.

5. Select a Bambda.

6. Click Load.

If the Bambda is error-free, it's added to the Custom actions side panel, ready for use.

Burp displays any errors in the Compilation errors panel of the Custom actions editor. You'll need to fix these before you can add the Bambda to the Custom actions side panel. For more information, see Troubleshooting Bambdas.

Creating Bambdas

You can write your own custom action Bambdas to meet your specific requirements.

For more information, see Creating custom actions.

Running custom actions

From the Custom actions side panel, you can run Bambdas manually and configure them to run automatically after a response has been received for a sent request. Your custom action Bambdas are available from any Repeater tab.

You can apply custom action Bambdas in the following ways:

• Run - Click to run the Bambda manually.

• Auto-run on send - Click A to enable auto-run. The Bambda runs when you send a request in the Repeater tab with auto-run enabled.

Bambda output is shown in the Output panel. To clear the output, click Clear.

Managing custom actions

You can manage your custom actions Bambdas from the Custom actions side panel:

• Edit - Click beside the Bambda you want to edit.

• Rename - Right-click the Bambda, then select Rename.

• Save a Bambda to your library - Right-click the Bambda, then select Save to library to store it in your Bambda library.

• Save a copy of a Bambda to your library - Right-click the Bambda, then select Save copy to library. A copy of the Bambda is saved to your library. This replaces the original Bambda in the Custom actions panel.

• Remove from list - Right-click a Bambda that is saved in your library, then select Remove from list. The Bambda is removed from the Custom actions side panel but remains in your library for future use.

• Delete - Right-click a Bambda that isn't saved in your library, then select Delete. This permanently removes the Bambda.