Is a Slack channel/group/im/mpim id unique across different teams? In other words, can two teams have channels with the same id?
I read the docs, searched on Google and here on SO, but could not get confirmation if channel IDs are unique or not.
Slack plans to clarify this in documentation soon. While in the present day you'd probably get by just fine assuming IDs are unique across different teams, we strongly recommend scoping all of your storage and retrieval by team ID.
Essentially, we recommend considering IDs as only unique within teams, regardless of if experientially they are globally unique.
This is the best way to protect yourself for the future.
来源：https://stackoverflow.com/questions/35566439/is-a-slack-channel-id-unique-across-teams