Based on our record, Slack RTM API seems to be more popular. It has been mentiond 1 time since March 2021. We are tracking product recommendations and mentions on various public social media platforms and blogs. They can help you identify which product is more popular and what people think of it.
Oh, my bad, in that case you probably have to use the Real Time Messaging API for Slack. Source: over 2 years ago
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