Invisible Hand: Firefox extension can save you money on online purchases


Invisible Hand is a free Firefox extension that kicks into action when you visit any of a number of well-known online shopping sites. It can monitor the pages you are browsing and notify you if the items you are looking at are available at a better price in any of the other sites on its network.

There’s a big debate that’s started after the latest economic crash over why or whether the previously dominant “Efficient Market Theory” in economics has failed and been discredited. It is now thought that one of the main premises that underlie this theory, that of “perfect information” in the marketplace over time is an unrealistic assumption that simply is never the case.

And though it will not save the Efficient Market Theory, Invisible Hand will definitely make your online shopping activity more intelligent by giving you instant access to the best prices that may be available with other vendors for the items that you are shopping for. Here are more notes:

  • How it works: Invisible Hand works in the background while you surf. If it detects that you are looking at any of the sites that are among the network of shopping sites that it monitors, it will immediately scan the other sites on its network, fetch other available prices, and display these as clickable links in a toolbar on your page.
  • Sites that are monitored: seem to over-represent books and electronics stores (including Amazon, Borders,, Best Buy, NewEgg, as well as many others). For a bigger list look here. There is somewhat of a bias for US and UK outfits.
  • Accuracy: in my experience testing of this software it was able to find accurate and useful information and lower prices on many items that I would typically shop for. Note, however, that in many cases shipping charges can be misleading, resulting in inaccurate recommendations (as an example, recommending something on site A that may cost 9$ with a $3.99 shipping charge over the same item on site B priced at $10 with free shipping).
  • Performance: the question here is how responsive Invisible Hand is and how quickly it can query and retrieve information (as well as how bandwidth intensive it is). Unfortunately I cannot really answer this question; all I can say from a purely subjective perspective is that at times it seems to take longer than I expected for the data to be obtained, even with my hi-speed broadband connection.
  • Invisible hand iconThe user interface: there isn’t one. Look for the Invisible Hand icon (which is a downward pointing arrow, see image to the right) for some information on what’s going on. A grey icon means Invisible Hand could not find information; a green one means that it does have information, and you can click on it to invoke this info in the toolbar. There is an obvious need for a third color that says: I haven’t even started looking into this item, but will do so ASAP, and a fourth that says: this site isn’t supported, sorry.
  • Privacy: promises not to collect any information aside from the items you are browsing for.
  • No guarantees: it is quite possible that you are able to find a better deal on your own than what Invisible Hand recommends (although I would say it is unlikely).
  • Bugs: I’ve had the experience where Invisible Hand refuses to make recommendations on an item (I should say, states that it has no recommendations to make), even when it had provided information a few hours earlier. Restarting Firefox magically brought the info back.

The verdict: a great software for online shopping that can potentially save you money from the moment you install it. If I could wish for something (aside from the remarks in the “User Interface” section above), it would be the ability to switch this one off by default until such a time as I am ready to press a button and ask it to quickly check for other or better prices for whatever I am looking at at that particular moment. It seems that for it to constantly querying and checking prices all the time and on every page I visit would in most (but not all) cases be a waste of bandwidth.

Having said the above I will say that I am impressed with Invisible Hand, am certain it will come in handy, and will definitely keep it permanently installed in Firefox. The FAQ page suggests that an Internet Explorer version may be in the works.

Version Tested: 1.5

Compatibility: Firefox 2.0-3.5

Go to the Invisible Hand home page to download the latest version (approx 41.3K).