An extremely weird problem I’ve started to have recently is that basically whenever the launcher tries to download any updates, it literally kills my Internet connection, as if it’s somehow overloading the router. Basically the download starts, ramps up to a reasonable download speed level for about 30 seconds, and then abruptly stops - but it’s not just a Blizzard server connection, but literally the Internet connection “dying” - i.e. PC and phone drop WiFi connection, and the led indicator on router goes from green to yellow, indicating there’s no Internet. After a while it comes back and the process starts again.
In this manner it took me several hours to install D4 - I basically have to let the Internet die, then come back up, download a few extra %, then die again, and so on. The actual gameplay is fine.
This happens both on my desktop PC and gaming laptop, and I’ve tried connecting to two separate routers (one in my home office, one that directly receives the fiber optic cable from the ISP that then feeds the home office router). In fact on my laptop I’ve downloaded the D4 update in a hotel in another country, and the behavior was similar (launch, ramp up speed, drop to ~0 for several minutes, start again). The actual internet connection there was good - latency in-game ~60ms and download speeds of ~100Mbps. Once the game was updated, no issues.
I have a good internet connection (optic fiber up to 500Mbps on a good day), everything else is stable and works fine - e.g. Steam downloads, various types of streaming content, actual gaming. The issue reproducibly happens specifically and only with launching Blizzard updates, on two separate computers.
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I have the same problem, thought something was broken with my net, but its the damn battlenetapp totally killing my whole house, 2 different routers and the netbox. How is it even possible
Same Problem for me. Thought it was my connection. But it is only with the BattleNet Launcher and can be replicated every time since 3-4 weeks. Cant play DIablo because of this because i cant download the updates.
facing exactly same issue here. connection going on / off, downloads / updates impossible.
Same Problem,
every time an update for Diablo IV starts to download,
the connection in the whole house broke down to zero and
the download speed broke to some kb/s.
We’ve got a 1000 MB/s connection, how is this possible?
So out of curiosity, does anyone from Blizzard actually read this forum? It is clear that this is an actual technical bug that, although it seems to affect a minor portion of users, is quite serious and game-breaking - so at the very least it would be interesting to understand if this is something the tech team intends to look into. A game download should not be able to kill the entire internet connectivity…
I’m in Europe but I was looking if anyone else has that weird issue.
I have a 1Gb/s fiber, so it isn’t that easy to saturate it. I suppose the Battle.net app opens way too many parallel connections or something like that when patching. 
I am not in the US either, just used US forums as they seemed more active.
Very clearly there’s a specific issue with the Battle.net app. I have most recently downloaded the entirety of BG3 from Steam in one go with no hiccups (and that’s a 100Gb download), yet patching D4 keeps bricking my optic fibre connection (first brick was at just 18% for the rather small 1.1.2 patch). Would be good if someone from Blizzard would actually acknowledge their awareness of this (probably not very common, else there’d be more complaining) issue and whether they intend to look into it.
I too have “connection issues” while the Bnet app is actively doing something.
I have the same issue.
I tried limiting my speed, hoping the client would also limit the amount of connections it would try to establish. This worked for me.
I actually set the limit really high, i have a 1 Gbit/s connection, so i tried setting my download limit to 100MB/s (100000KB/s in the client. and my download went through, with some weird spikes.
This is not an ideal solution, hopefully blizzard will get it together and fix this. It seems to be an issue you should not experience in 2023.