If you use Hangouts on the web, you'll be familiar with the fact that Google has changed things up with the app a couple of times over the past few years. At first, Hangouts was only accessible from Gmail and inside of Google+, then Google finally launched a standalone application for Chrome and gave it a chat heads style interface. In its most recent and current design iteration, Hangouts for the web now displays as an open window that has the list of conversations on one side with the open conversation on the other. To some, the new Hangouts can feel a little bit messy, and today Google has integrated a new option which allows users to clean things up just a little bit.
This new feature added to Hangouts on the web is called "Dense Mode" and the idea behind it is to help users feel like Hangouts is a little less cluttered. If you enable Dense Mode what it will do is remove the avatars and recent messages from the window so that you have a more condensed view of things. This surely won't be to everyone's liking, so naturally, it's just as easy to disable Dense Mode as it is to enable the new feature.
To access it and try things out, or just to see how it looks, all users have to do is open up the settings menu after opening the Hangouts for the web app. There will now be a little box that states "Use Dense Roster" that you can check, and once done the avatars of each conversation will disappear from the side that is listing all of your conversations. This looks a little more dated and such, but if you don't care for the avatars and profile pics you now have a way to get rid of them so the list of conversations only shows contact names. If you don't care so much to read the names of every conversation in the list, this new Dense Mode feature is not for you as it is likely simpler to just look at the avatars and see who is messaging you.