Mermaid Preview alternative: from /mermaid to diagrams your team can edit

Mermaid Preview does one job well: type /mermaid, paste code, get a PNG in the channel. It is free and open source. Teams usually look for an alternative when the diagram starts to change and a new PNG every time is not enough.

Direct answer: Arialine is a Mermaid Preview alternative for Slack. It covers the same workflow — a slash command (/arialine), paste Mermaid, rendered diagram in the channel, no AI needed for valid code — and adds an interactive HTML file, saved source, edits by replying in the thread, version history with Undo and Rewind, exports, and diagrams generated from plain language.

Everything Mermaid Preview does

Mermaid Preview	Arialine
/mermaid opens a dialog	/arialine opens the New diagram form
Paste Mermaid, post a PNG	Paste Mermaid, post a PNG and interactive HTML
Renders Mermaid diagram types	Renders the types in its Mermaid 11 renderer
No AI involved	Valid Mermaid is rendered without AI

What Arialine adds

• Source kept with the diagram. Export .mmd, PNG, SVG, or a PDF report of one or several versions.
• Edit in the thread. Reply "@arialine add a retry step after Payment" and the same diagram becomes version 2.
• History you can trust. Each version links to the Slack message that asked for it; Undo, Rewind and Branch are one click away.
• More ways in. Mention @arialine with a code block, share a .mmd file, or use the Render as diagram shortcut.
• AI when you want it. Describe a diagram and Arialine writes the Mermaid; invalid code can be repaired.
• Markdown to Canvas. Share a .md file and Mermaid blocks become images in a Slack Canvas.

Move over in one minute

1. Add Arialine to Slack and invite it: /invite @Arialine.
2. Type /arialine instead of /mermaid.
3. Paste the same code and press Create.
4. Reply in the board's thread to change it.

When to stay with Mermaid Preview

If you only need a picture, want a fully open-source tool, and prefer that no copy of the diagram is kept, Mermaid Preview is enough. Arialine stores the board's source and history on purpose, so the diagram can be edited later; its Free plan allows 3 boards.

See the full Arialine vs Mermaid Preview comparison.