It's VERY memory heavy. When I open 4 channels it could eat as much as 4GB, comparing to 300MB per card when it's open in Chrome. That's why I started writing Chrome App which will simulate native Slack client and be much more memory efficient.

As another commenter mentioned, it's extremely memory hungry. Right now, it's got 6 processes running, and it's chewing through a little over a gig of ram. I frequently (roughly once a week or so?) check process explorer and find slack hung and sitting on 3+GB.

Performance is sluggish on both the high end machines I use regularly (Dual xeon workstation, and an i7 6700k with 32GB/16GB ram respectively). The search functionality brings the UI to a halt, and scrolling through the message history isn't remotely close to smooth. Startup times are also quite long. I closed the app, and re-ran it. it was 5 seconds before the window appeared, and another 5 before my chat window was populated.

Slack is pretty good for a web app. You can tell they really worked hard to make it feel native.

But there are just some fundamental differences between desktop apps and web apps.

Just like a website, the Slack desktop app is slow. Open Apple Messages, and you'll see all your messages instantly. Open Slack, and you'll be greeted by a loading screen, followed by a loading screen with an insightful quip. Click on a different channel, and you'll see another loading screen, followed by another loading screen with a different funny message.

And then there are all these inonsistencies... Holding down the mouse on a popup menu doesn't work; you need to click to open, then click again to select. Resizing the sidebar is not possible.

All those Electron apps are extremely slow on my mac (Intel Core 2 Duo mid 2010, 4Gb RAM). I am using Slack web version (in Chrome also) and can't find any difference, except it is just a tab among others.