slack-copy

Markdown on the clipboard, ready to paste into Slack.

Requirements

• macOS (the clipboard write goes through osascript; with --no-copy the converter prints on any platform)
• Node.js 18+

Install

From npm:

npx slack-copy message.md
# or
npm install -g slack-copy

Pre-publish, run it straight from GitHub:

npx github:finnjanssens/slack-copy message.md

Or as an Agent Skill for Claude Code, Cursor, Codex, opencode, or any other agent the skills CLI supports:

npx skills add finnjanssens/slack-copy -g        # every detected agent
npx skills add finnjanssens/slack-copy -g -a claude-code   # one agent

Or manually:

git clone https://github.com/finnjanssens/slack-copy.git
ln -s "$(pwd)/slack-copy" ~/.claude/skills/slack-copy

See SKILL.md for the skill instructions.

Slack's default composer is rich text: the one with the B I U toolbar. It does not interpret mrkdwn, so pasting *bold* or <url|label> into it leaves the asterisks, pipes and brackets sitting there literally. mrkdwn is only interpreted for messages sent through the API, or when you turn on the "format messages with markup" preference, which replaces the rich composer entirely.

So this puts two clipboard flavours down at once:

• text/html — what the rich composer actually reads. Pasting produces real bold, lists, code and links, with no Slack setting involved.
• plain text — mrkdwn, as a fallback for markup mode and for API posting.

Usage

npx slack-copy message.md                              # convert and copy
npx github:finnjanssens/slack-copy message.md          # pre-publish, from GitHub
cat message.md | npx slack-copy
npx slack-copy --no-copy msg.md                        # print only
npx slack-copy --html msg.md                           # print the HTML it copies

Reads a file argument or stdin. Prints the mrkdwn on stdout, since it is the readable one to eyeball. macOS only: the clipboard write goes through osascript, because pbcopy can only carry plain text.

Conversions

See references/conversions.md for the full Markdown → mrkdwn/HTML table.

Test

npm test        # unit suite + eval rows
node evals/check.js   # evals only

test.ts is the unit suite; evals/ holds the data-driven evals: one row in evals/cases.json pins one behaviour, and evals/check.js reports by row ID. A new behaviour is a new row, and CI runs both on every PR.