Web Essentials 2010 is the first version and doesn't have most of the features in the newer versions.Download
If you want to install an older version of Web Essentials 2013, please visit the GitHub releases page.
The GitHub releases page contains several files per version. The extension to install is the .vsix file.
If you already have Web Essentials 2013 installed, you must first uninstall it if you wish to install an older version.
You can now get the latest nightly builds of Web Essentials 2013 automatically delivered in Visual Studio. These builds aren't actual nightly builds, but will be updated several times a week.
This is recommended if you need specific bug fixes and can't wait till the next official release or you just like to live on the cutting edge.
The purpose of the nightly builds is to make sure that you always have the latest and greatest, as well as help the Web Essentials team to find bugs earlier, so they can be fixed before the next official release is published.
You will still be notified by Visual Studio to update to the official builds. The nightly builds simply gives you more updates between the official releases.
In Visual Studio go to Tools -> Options -> Environment -> Extensions and Updates.
Click the Add button and fill in the name and URL fields.
Name: Web Essentials 2013
And finally click the Apply button.
That's it. You've now added the nightly feed to Visual Studio and updates will start to show up in Tools -> Extensions and Updates dialog
If you just want to install the latest nightly build without setting Visual Studio up for the nightly build following the steps above, then you can certainly do that too.
By installing the nightly build directly will still make Visual Studio alert you when an update to the official release is ready to be installed. This option is good if you just want to try out the latest and greatest but don't want to opt in to the frequent updates coming in the nightly feed.
Direct download: http://vswebessentials.com/nightly/feed/webessentials2013.vsix