Bandwidth+ is a free app that can monitor your bandwidth usage. The app runs on your Menubar. Its icon displays how much data has been transfered since it is running. This is the addition of download plus upload transfers, by default. But you can set the app to show only uploads or only downloads. When you click on the icon, a small window will pop-up. This will display the name of your wireless network, and how much data has been uploaded, downloaded, and the total.
Bandwidth+ was apparently designed for users who have a monthly bandwidth usage limit, or a quota. Thus, it comes with an interesting feature that should be of use to those users. In the Preferences window, this feature is called Monthly. You simply select your network, what type of transfer you want the app to keep track of (uploads and downloads, uploads only or downloads only) and you specify what your quota is. When you do this, a bar will be displayed every time you click on the Menubar icon showing you how much you have used, and how much is left. If you have some bandwidth left, the bar will be green, when you are running near your limit it will be yellow, and once you pass it, it will be red.
In short, this is a great app for anyone who is interested in how much bandwidth they use over the course of the month. Unfortunately, the app doesn't let you see exactly how much data you have transfered in a specific time frame.
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