The Invisible Hand add-on for Firefox is an unobtrusive add-on that will notify the user if it knows of an Internet shop that is offering the product for less than the current shop the user is visiting. It will display a row beneath the tabs in Firefox whenever it found a shop with a lower price. The system only works if the user is visiting one of the 50+ supported Internet shops in the United Kingdom or United States.

The bar with the better price will not appear if there is no better price or if the shop is currently not supported by the Firefox add-on. There are currently a few problems associated with the add-on that I would like to outline below:

• Supports only 50+ shops in the UK or US. That’s ok for popular items but no where in the range that the price comparison services offers.This also means that users from other countries have no use for the add-on unless they do shop in the US or UK.
• A click on the better price button (or the other retailers button) will open that website in the same tab. There is no way of opening the site in a new tab or window.
• The service does not add (potential) shipping costs to the price comparison. It can be that the price at a lower price shop can turn out to be higher if shipping costs are added to the price.
• The service sometimes fails to find the right product. A Guitar Heroes 5 bundle with hardware for the Nintendo Wii for example was said to be about 30 Pounds cheaper at another retailer. It turned out to be that this was the version of the game without the hardware.
• The price comparison is restricted to the same country. It is for example not possible to see if the price in another country is cheaper than the price in the current country. This is probably linked to the shipping costs problem. It would make a lot of sense once more countries of one continent (e.g. Europe) are added so that users from one country could check if the product is a lot cheaper in another country (which often is the case if you look at the German and UK Amazon shop for example).

The service is currently in beta and the developers have already mentioned that they are working on several of the problems listed in this article. Invisible Hand is nevertheless an interesting alternative for Firefox users from the UK and US who do a lot of online shopping. Interested users can take a look at the developer website to see the list of supported retailers or download the add-on from the Mozilla Firefox website.

The Firefox add-on adds itself to the right-click menu. If a phrase has been selected on a webpage it will offer to search for it on various price comparison sites but also directly on shopping sites like eBay, Amazon and various other shopping portals. The sites that are displayed in the right-click menu can be configured by the user. There is however no option (currently) to add custom sites to the list. Only the sites that the software developer has added can be selected.

There is however a large selection of price comparison sites and shopping sites available and it is up to the user to add the ones that he is interested in or regularly using.

The selected shopping portal or price comparison site will be opened in a new tab in Firefox. There is also the option to search for the product in all sites in a category. This simply opens all of the sites in a new tab.

The author provides an option to suggest new websites which might be added to the database of sites at a later point in time. The Firefox add-on comes with a second option. If no text has been selected a right-click and the selection of RightClickBuy from the context menu will open a search form that can be used to search for products on a selected website.