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HttpFox: Data Checking Tool for Firefox

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Httpfox is a Firefox add-on that is handy for checking that your data is being recorded correctly as you build explicit questionnaire items. This entry shows you how to get HttpFox in your Firefox broswer and how to use the Add-on to check your data.

First, a reminder: Firefox is the default browser for previewing study materials and the data that comes from them. However, it is supremely important that you preview your study (every task) in other browsers. Internet Explorer is the browser that most commonly displays tasks differently. It’s also a good idea to look at your study using Chrome, Safari, and/or Opera.

Downloading Httpfox

First, make sure you have the latest version of Firefox (go to to find out if you need an update). Then, in a Firefox browser, go to Tools ► Add-ons. In the search bar, enter “HttpFox”. The results should have HttpFox 0.8.9 listed. Click “Install” and proceed through the warning about non-trusted add-ons.  To complete installation and start to use Httpfox, you will need to restart Firefox.

Opening Httpfox

When you open a Firefox browser, go to Tools►Add-Ons► Httpfox► Toggle Httpfox (you can also just hit Shift + F2). Depending on your Firefox display, you may also see a small icon of a blue circle with green and orange arrows in the lower right-hand corner of your screen that you can click on to open Httpfox.  Three boxes should appear in the lower section of your window. You can resize this section by pulling up or down on the top line of the section.

Using Httpfox

To preview the data for a particular task, open up the task in your browser. For least annoying results, close other tabs you may have open in that window (especially email!).  This will decrease the amount of extraneous information that is displayed in the Httpfox box.

With Httpfox open, click the “Start” button on the upper left corner of the httpfox box.

Answer the items in the task and pay attention to what data should be recorded (that is, don’t just answer randomly. Write down or otherwise keep track of the responses you enter so that you’ll know whether the output is correct).

After you have answered all the items (or intentionally left them blank), hit the button at the bottom of the page that, in a normal study, would lead to the next page in the study.  In the main browser window, you will receive an error message. Because you are looking at a task that is not part of a larger study, you have no active study session.  At this point, a line in the upper box should appear in the Httpfox box. The URL (in the right-hand column) in this line should say something like this: Click on that line once to highlight it.

Next, look below that first box to see five tabs (Headers, Cookies, etc). Click on the POST Data tab. You should now see a series of lines in the lower box of the httpfox add-on. If your data is recording correctly, you should see lines for each of your variables. The variable names are identified in the “Parameter” column, and the values that would be recorded (had you actually been taking a study) are listed in the “Value” column.

Make sure that each of your variables show up in the left-hand column and that each variable has the correct Value that you expected on the right. If anything is amiss, go back to your file and investigate the issue.

A few tips

  • If you want to stop recording, hit the “Stop” button, which is next to “Start”
  • You can close the Httpfox box without stopping the recording. Simply click the red “x” in the upper right corner of the Httpfox box
  • If you want to get rid of the recorded material that’s piling up in Httpfox, click “Clear”, which is next to the Stop button.
  • You can run an entire study while using Httpfox. However, each task will show up as a separate line in Httpfox. Often, there will be multiple lines for the same task, so you may have to scroll through some lines to find your data from each task.