Known Issues - Calls on iOS

This is a list of known issues for those of you using Calls on Slack for iOS 2.90.

If you experience a problem not included on this list, email or type /feedback and your issue into Slack to report the problem. And then we’ll fix that one too!

  1. Users occasionally would see unhelpfully truncated error messages. Seeing "Ahmed has Do Not..." as an error message is not as useful as one including the words “…Disturb mode enabled”. Particularly if you’ve already called him to ask what it meant.
  2. Sometimes we show a "Call Ended" message when you didn't choose to end the call, rather than (more correctly, and politely) an error message about why the call had to end so suddenly.
  3. In rare cases, just after installing the app, calls can fail due to two embarrassing problems:
    1. A rare bug where we think you are on a call with yourself. So we say "user is on another call," which you both are, and, simultaneously, aren’t. :grimacing:
    2. You call someone… but we don't ring them. So, unsurprisingly, they never pick up.
    3. Call has therefore failed. On multiple levels.
  4. Sometimes the avatar goes off-center on an iPad. Which is damaging to aesthetics, but not call quality.
  5. If you try calling from 2 (or more) devices simultaneously and then muting one device, both devices will show a muted icon, even though you are only muted on one device. So beware: everyone can still hear you. And you can hear them. Saying things like: “Why are you calling from two devices? Why would you do that?”
  6. When receiving a call on an iPad and the Mac App, if you accept from the iPad, the Mac App will still continue to ring. (Expected behavior is that if you accept on one device, all others stop ringing, which we’re busy fixing). Sorry to bother you with so much unnecessary ringing.
  7. In Group Calls it actually says MPDM in several places. There’s logic: That’s our old internal acronym for a group direct message. But you didn’t need to know that.
  8. If you reconnect to a call, you will see yourself in the participant list twice. As you know, you can only be yourself. And that is enough.
  9. What happens: when user A is calling user B and user B has not responded yet, but then user C calls user B.... user A's call gets cut off. In other words, a bug with Call Waiting. It’s complicated, but basically: Call Waiting doesn’t work as you might expect. No one’s cutting anyone off intentionally, it’s all just bugs. Always assume good intentions.
  10. There may be reconnection issues when moving through areas where you’re switching from wifi to cellular data and back, meaning that sometimes the call won't reconnect. This is unfortunate on a mobile device, and high on our priority list.
  11. In very rare instances, users may get a message saying they “can't start a call because they are on another call”, when they are not, in fact, on another call. “But I am not on another call.” they might very reasonably say. It is true, they are not.
  12. If, during a call, you plug in headphones, and tap on speaker (e.g. speakerphone), audio won’t route to iPhone just won't. You want it to, but it won't. One day it will.
  13. If a call goes over 1 hour, the call duration can no longer be trusted. It’s “more than an hour” though, if that helps.
  14. Some elements of call UI on an iPhone 4S might overlap, which is phonist. We’re working on improving this.
  15. If you’re on a call on an iPad, and the Slack app gets backgrounded you won't be able to tap on anything when the call ends and you return to Slack. Killing the app and restarting fixes the issue.
  16. Even if speaker is off, the first two rings get routed to the speaker. Sorry about that.
  17. If user is on a team with Calls disabled, they will currently still see /call in the slash command list. If a user on a team with Calls disabled tries to use the /call slash command, she will get a response "invalid command" which it is, but we could be more helpful in our manner of telling you so.
  18. If you are signed into two iOS devices and purposefully try to call your friend on both at the same time, the app is going to say your teammate is busy. The fact we know this proves that it is something that people have tried to do. Why, we do not know. We are teaching the app to be smarter about this in the future, but for now, while we are still in the past, please… just… don't?
  19. Sometimes when user signs into a new team that has Calls enabled we don't register this fact quite fast enough, so they can't receive calls via push notification (which is the main way that one receives Calls). Killing the app and restarting fixes it. We just need a little kick sometimes.
  20. Any audio that is currently playing before a Slack call (incoming or outgoing) should fade out when the call begins. But it is not. Instead the Slack call merges with the music (or whatever) playing in the background. Users may hear their music and the other people on the call at the same time. Users on the other end of the call will only hear your voice and not the music, which is unfortunate, as otherwise we could legitimately call it a karaoke feature. Instead, we are fixing it.
  21. User is able to pin/star the call cells. This will not have any affect on the outgoing or incoming Slack call. In the later versions we have removed the ability to pin and star the call cells, so users should be discouraged from using this feature. We never meant to let them do that. Mainly because it makes literally no sense.
  22. Sometimes, even with wifi that is not too bad, you may get a message that it is not possible be on a call without being connected to the internet
    1. To avoid this problem, switch to a better network and try calling again. We are working to lower the app’s high standards and work on a fix to help calls work on wifi that is, frankly, good enough.
  23. In an ongoing Slack call, if a user opens music file stored on Slack then it may break the call for some, while others may hear some weird noises. To avoid this problem, just don't open music files while on a Slack call. Why would you do that? You wouldn't do that. Don't do that.
  24. Sometimes in calls started from within a direct message users may not be able to hear one another. This happens very rarely, but is a pretty fundamental failing. Start the call again and it should fix itself. And then we will fix it. And everything will be wonderful.
  25. Currently, it is not possible to use bluetooth devices with Slack Calls. You are still tethered to your phone, for now.

NB: We realize that the post above may occasionally read like a comedy post about the most ridiculous bugs imaginable, but it is not, we swear it.

If you don't see your particular issue listed here, congratulations! You may have discovered a hitherto unrecorded bug! Email us at or type /feedback and the problem into any Slack message window to report it. And thank you!