Read a Slack Canvas as Markdown

slackcli canvas lists Slack canvases and reads them as Markdown, which makes them usable in a terminal, a diff, or an AI agent’s context.

canvas list

slackcli canvas list
slackcli canvas list --limit=50
slackcli canvas list --channel=C1234567890     # canvases shared in one channel
slackcli canvas list --json

Option	Default	Purpose
--limit <number>	20	How many to return (1–1000)
--channel <id>	—	Channel ID, URL or name ("#general") whose shared canvases to list
--workspace <id|name>	—	Workspace to use
--json	off	JSON output
--fields <list>	all	With --json, only these comma-separated fields (dot paths allowed)

With --json, an empty result writes nothing to stdout and exits 0.

canvas read

# By canvas file ID
slackcli canvas read F1234567890

# From its Slack URL
slackcli canvas read https://myteam.slack.com/docs/T012AB/F1234567890

# The canvas attached to a channel or DM
slackcli canvas read --channel=C1234567890

# Raw HTML, no conversion
slackcli canvas read F1234567890 --raw

# JSON, with the Markdown in a `markdown` field
slackcli canvas read F1234567890 --json

Option	Purpose
--channel <id>	Read the canvas attached to this channel or DM
--raw	Print the source HTML instead of Markdown
--workspace <id|name>	Workspace to use
--json	JSON output including metadata and the Markdown
--fields <list>	With --json, only these comma-separated fields (dot paths allowed)

--raw takes precedence over --json: with both, stdout carries the HTML, not JSON. --fields then has nothing to select from and is ignored (it is still validated).

Canvas IDs are file IDs: F followed by alphanumerics. Either give one or use --channel (the canvas ID wins when both are given). A channel with no canvas is reported on stderr with exit code 0 and nothing on stdout. An unknown canvas ID exits 1 with Slack’s error.

What the conversion handles

Slack canvas exports are Quip-based HTML with custom elements. The converter is dependency-free and covers headings, bold/italic/strike/code, links, ordered and unordered and nested lists, task lists, blockquotes, fenced code blocks (preserved verbatim, so inline tags inside them are not mangled), tables as GFM, embedded files and links, and emoji.

<@U…> and <#C…> mentions are resolved to display names and channel names after conversion, so you get @Rafael and #engineering rather than raw IDs.

Limits and failure modes

• Downloads are capped at 10 MB; a larger canvas is refused rather than buffered.
• If the download comes back as a Slack sign-in page — which is what an expired token produces — SlackCLI detects it and tells you to re-authenticate instead of printing HTML at you.
• Reading a canvas needs file-read permission: files:read for standard tokens.