Editors' Note: The Download Now link will prompt a local download of the Firefox extension. To install the extension directly, open the file using your Firefox browser.
Use Tamper Data to view and modify HTTP/HTTPS headers and post parameters. Trace and time http response/requests. Security test Web applications by modifying POST parameters. FYI current version of Google Web Accelerator is incompatible with the tampering function of Tamper Data. Your browser will crash.