Pidgin

The interface is rather simple and it doesn't seem to have the degree of customizability that Miranda IM enjoyed in its golden days. But it's still good - will take after your native system theme without introducing any visual bloat. The Tango icons are pretty nice, much better than the ugly flat/line nonsense you see everywhere.

Functionality is also pretty bare-bones and traditional, but it will most likely satisfy your chat needs. The custom smilie function is fun! There's no shady crap like ads or server redirects too. The novel approach to accounts, keeping multiple, i.e. possibly different protocol users online might seem a bit weird at first, but it doesn't really get in the way once you get the hang of it, plus it might be actually of use to some. Very light on resources. This is a perfect program for XMPP/Jabber users.

Tip: if you want something other than the default status icons or smilies, go here . If some themes don't seem to work, rename the images in them so that there's no spaces, and edit theme.xml file so that it points to the correct files.

I have fond memories of Pidgin from the 90's. I want to like it. But it's clunky AF. The clincher for me is that the lurch OMEMO plugin just does not play nice with others. Hit or miss (mostly miss) on sending out messages. They are never received and messages like this are delivered from the servers instead, "I sent you an OMEMO encrypted message but your client doesn’t seem to support that..."

I really wish one of these desktop apps would follow the example of something like the android app blabber.im. Examples of a clean UI and flawless performance are out there.

The best I've found so far for a windows client is Gajim, it has gotten OMEMO to work most of the time. But it's also stuck in a bygone era of fledgling UIs.

It takes 85Mb of space. OTR is not built-in. It must be found elsewhere. It's titled "pidgin-otr-4.0.0-1.exe". It works. Overall a problem-free program. XMPP works fine. Can be encrypted with OTR. Nearly all others were defective in one way or another, but this one is functional. Connects and sends messages and receives messages well.

Pidgin does not support Facebook Messenger, but the Purple-Facebook plug-in does.

https://github.com/dequis/purple-facebook/wiki

It works with most platforms it just works

Note: The only reason I don't give it 5 stars is because the interface is wicked dated (like pre-Windows XP dated). With a UI update (yes, I know how much work that would be) Pidgin would steamroll every other messenger on the planet.

Yo, this is easily the best messenger app I have ever used. I've been building computers for well over 20 years, so I've seen a lot of messaging clients come and go. Pidgen, thanks to some lovely http hacking, is compatible with protocols that no longer have an API (specifically I'm thinking of Facebook Messenger, but I'm sure there are other gated protocols that it supports).

The sheer volume of plugins for Pidgin is frankly insane. It has a plugin system based on libpurple, so it supports a lot of functions that are overlooked in many messenger apps. For example, autoresponders, which are nothing short of brilliant for people like me who have ADD and juggle tens of messaging platforms to stay in touch with people. Without being able to shoot back a quick "I'll get back to you shortly..." people start to think I'm ignoring them (I'm not).

There are tons of other plugins that do all kinds of housekeeping and automation as well as (of course) connect to other messaging protocols, some of which are inaccessible with commercial apps.

Installing plugins can be a little bit tedious for the non-savvy, but really isn't that hard (for the ones that have docs anyway). Generally, you just unzip a .dll to the plugins directory, restart, and Bob's your uncle. Connecting to Facebook messenger was actually quite a bit easier than Hangouts (yep, supports Hangouts via Gtalk protocol).

Without a doubt, the most robust, extensible, user-friendly and powerfully versatile desktop IM client available, and it's FOSS on top of that! Highly recommended.