Firefox did not have a comparable built-in feature until now. Users who wanted to install experimental features had to go to the Mozilla Labs website or the Firefox add-on repository to do so.

This changes with the introduction of Mozilla Labs’ Lab Kit, a new Firefox 4 add-on that pushes new experimental features right to the user’s web browser.

For now, only three experimental add-ons are available: Test Pilot, collecting “structured user feedback through Firefox”, Speak Words, an add-on that we have reviewed earlier and Contacts, which we did review earlier this year as well.

Users who install Lab Kit will automatically install all add-ons that it contains. For this initial release it means that all three add-ons are pushed to the browser. Test Pilot and Contacts require a restart of the browser, while Speak Words functions right away without restart.

The way this is implemented is not the most user friendly in my opinion. Pushing all add-ons of the Lab Kit to the browser without offering an option to customize the selection may turn away many users who otherwise would be interested in trying out those experimental features.

It is however possible to uninstall the add-ons individually after installation of the Lab Kit, but it is not clear at this moment how this will affect future add-on updates.

Major updates to contents of the Lab Kit are shown to the user in form of a notification, Lab Kit surely is an experimental feature as well, and it is likely that the developers will add options to customize it in future versions. The most pressing feature that is currently missing is a selection menu to only install and monitor selected experimental add-ons. (via)

Experimental on the other hand did not reflect the unreviewed state of the add-on that well which is probably the main reason why Mozilla switched from listing this add-ons as experimental to unreviewed.

Mozilla users who visit the add-on repository now will only find one optional checkbox entry in the add-on listings called “Show unreviewed add-ons” which will add unreviewed add-ons to the list of displayed add-ons.

The Add To Firefox button next to each add-on has also been changed to give the user visual information about the add-on. Unreviewed add-ons are displayed with a yellow button and a Not Reviewed text beneath them while reviewed add-ons are still shown with a green button and no additional text.

The extension repositories have changed in another, important manner. A user visiting the Mozilla website with a supported product, e.g. the Firefox web browser, will now see in the general add-on listings if the add-on supports the installed version of the product.

Add-ons that are not available for the Mozilla product of the user are shown in a lighter yellow with a red icon and the text Not available for “product name”.

Visual indicators have also been added when a user clicks on an unreviewed or unavailable product. A click on an unreviewed add-on will display an overlay with the text “Caution: This add-on has not been reviewed by Mozilla. Be careful when installing third-party software that might harm your computer.”

A click on the Add To Firefox button will install the add-on nevertheless.

An add-on that is not available for the software version installed on the user’s system will display the warning “This add-on has not been updated to work with your version of Firefox.” with the option to install anyway.

A combination of the two visual reminders is also possible (for unreveiwed and unavailable add-ons). While we are at it, the add-on listings can also display the two white boxes Add to Firefox and Continue to Download.

The white Add to box basically indicates an incompatible add-on while the continue to download box indicates that an End-User License Agreement has to be accepted before the add-on can be downloaded and installed.

What’s your take on the changes introduced?

The only requirement is to install the Copy and Paste add-on for Firefox on both computers and configure them accordingly. Configuring means setting up the other computer’s IP – be it local or remote – and the port that should be used to establish the connection.

The extension provides the means to check if a connection can be established and will display the information in the configuration.

Users who want to use this extension should note that this extension will send all text that is copied to the clipboard to the other computer. There is currently no way to turn it on or off whenever that feature is needed. This could be a privacy risk as there is no information provided how the data is transferred. Our guess is that the data is transferred unencrypted which could mean that anyone monitoring the network traffic will be able to access the data.

The add-on is currently in experimental stage and the author asked explicitly for feedback for his extension. It is very likely that he will add those buttons to a later version of his add-on to increase the security. As of now the only way to deal with this is to set the add-on to inactive or remove the IPs of the second computer whenever it is not needed.