This scope lets an app "post messages in approved channels & conversations"
This feature was exclusive to our workspace apps developer preview. The preview has now ended, but fan-favorite features such as token rotation and the Conversations API will become available to classic Slack apps over the coming months.
chat:write only works with workspace apps.
This OAuth permission scope works with these Web API methods.
chat.delete- Deletes a message.
chat.meMessage- Share a me message into a channel.
chat.postEphemeral- Sends an ephemeral message to a user in a channel.
chat.postMessage- Sends a message to a channel.
chat.update- Updates a message.