Split intentionally long messages into multiple postings of no more than 40,000 characters each, preferably less.40,000 characters is a lot for busy humans to read. Measure how long your messages can be.On Augwe'll reduce the maximum limit to 40,000 after a gradually lowering limits over several weeks. This behavior applies to all methods of posting messages to Slack: chat.postMessage, chat.postEphemeral, interactive message and slash command response URLs, incoming webhooks, and other ways to post. As with previous behavior, in addition to truncation you may find long messages automatically broken into multiple messages. When we truncate, we provide you a warning about it. Know now that messages with tremendously long text bodies will be truncated to (eventually) up to 40,000 characters. Previously, we asked you only to keep messages under 4,000 bytes but left the consequences ambiguous. The text field of messages is now limited to 100,000 characters, with the limit becoming 40,000 characters in August 2018. On Augwe started truncating messages containing more than 40,000 characters. Over the next several weeks, we slowly lowered the allowed character count. As of July 12, 2018, we truncate at 100,000 characters. We're tidying up the character limits on the text field of posted messages.īeginning April 25th, 2018, we truncated messages sent to Slack that are longer than 500,000 characters.