Today Slack has started throwing a spinner on me if I return to a tab after some interval (like 5 minutes?). It's kinda hard to even describe this eldritch horror, so bear with me: • I have a tab. It has Slack loaded on it all working. 🎈 • I switch tabs, go off and interact with some other site. • After some time I return to my Slack tab. • I'm faced with a white page with a tiny spinner in its geometric center. 💥 • A few (1-5) seconds later Slack returns. There's no sign of a page reload or anything. • I had to double-check, but I've definitely not restarted my browser or even closed the lid on my laptop in the interim. What.. is this? Is this some new idea in web development? I can't imagine what benefit it could possibly provide anyone. Is it a bug affecting just my computer? I can't conceive what sort of error of omission might lead to it.

I wonder if it's some way to deal with getting throttled in the bg? Like, the JS notices that it's been in the background for a while, meaning it doesn't get to check for fresh data, so instead of showing stale data they just block the ui and hit the server when you come back.

Ah that helps at least make sense of it. So the idea is that Slack is so mission-critical it can't afford to risk showing outdated information.. 😂

I don't see this, perhaps because I use the app rather than the website.

I use Slack in the browser, but I don't think I've seen this particular problem yet... (I'm using Firefox on macOS.)

There's a lot of factors that could be at play here: browser, device, device settings/context, HTTP caching/state, client side code, is a service worker involved etc. This behavior could be just one of those things e.g. bad client side code. Or a combination e.g. a device with "data saver" settings working with the browser to aggressively background inactive tabs not playing nicely with a service worker. As a data point I'm using Slack in the browser on MacOS and haven't seen this.

This is just a guess, but I'd assume this was the browser unloading the tab to save RAM, and scrambling to get it back! I feel like I've heard of browsers doing such things... but usually it appears from the user's point of view like a full refresh. For it not to have that behaviour the tab would have had to be snapshotted to disk or something...

Chrome has a "memory saver" which got turned on by default when it landed, but you can choose differently in settings, I think there are a few levels of aggression to select from! This background tab artifact could be because of that?