There's no way to automatically show edited text as strikethrough, though, so you'll need to first strikethrough old text then add your new message if you want to retain the original message when editing things.

The S button will strikethrough your text. Select text, then click the link icon in the formatting toolbar Select. Or, if your Slack account shows an Aa button on the right of the text input box, click that to show the formatting toolbar to give you quick access to Slack's text formatting options. UPDATE: Slack has finally added this functionality to their chat interface (source). Use the formatting button: Select text and hover your mouse over it, and Slack shows handy formatting options-the S button will strikethrough your text.Select your text, press that keyboard shortcut, and Slack will strikethrough that text. Use the Slack strikethrough keyboard shortcut: CMD/ Ctrl+ Shift+ X.Slack will then format that text strikethrough. Add a tilde before and after your text: The quickest way to type strikethrough text is to type a tilde ~, then type your text, then close with another ~ like ~this~.That gives you several ways to strikethrough text in Slack: Markdown is an easy-to-read, easy-to-write plain text format that can optionally be converted to HTML, which is commonly used in the open source community for documentation. What am I doing wrong None of the example Markdown links work so far in my Slack app. This is probably a coincidence, but after Mattermost announced markdown support last week, Slack announced the same feature yesterday. Slack uses Markdown-style characters to format messages, along with keyboard shortcuts and a new rich text editor. Slack Markdown for Links Are Not Resolving.

Slack markdown