Arialine does everything Mermaid Preview does in Slack — a slash command, paste Mermaid, a rendered diagram in the channel — and does it better, with interactive HTML, saved source, thread edits, versions and AI.
Start with Mermaid Preview
Mermaid Preview is a free, open-source app for one job: turn Mermaid you already wrote into a PNG in Slack. Its Marketplace listing documents on-demand generation without retaining diagram source or PNG copies on its servers.
A review with Mermaid Preview
Evaluate Arialine
Use Arialine when Mermaid source, addressed revisions and the source message behind each applied change need a shared board in Slack. Review generated output before accepting it.
A review with Arialine
| Capability | Mermaid Preview | Arialine |
|---|---|---|
| Slash command that opens a Mermaid dialog | /mermaid | /arialine |
| Paste Mermaid, get a rendered diagram in the channel | ||
| Mermaid diagram types (flowchart, sequence, class, state, ER, Gantt, pie, journey, timeline…) | ||
| Renders valid Mermaid without AI | ||
| PNG image in Slack | ||
| Interactive HTML file with pan and zoom | — | |
| Mention the app with a code block, or share a .mmd file | — | |
| Source kept with the diagram; export .mmd, PNG, SVG | — | |
| Edit the diagram by replying in its thread | — | |
| Version history with Undo, Rewind and Branch | — | |
| Each change linked to the Slack message behind it | — | |
| Generate Mermaid from a plain-language description | — | |
| Automatic repair of invalid Mermaid (optional) | — | |
| Markdown files with Mermaid blocks rendered as a Slack Canvas | — | |
| PDF report of one or several versions | — | |
| Works from Slack's AI assistant (MCP) | — | |
| Free and open source | Free plan; not open source | |
| Keeps no copy of the diagram | Keeps source and history so you can edit |
Add Arialine to my Slack/arialine → New diagram → pasteflowchart LR
A[Checkout] --> B{Payment ok?}
B -->|yes| C[Create order]
B -->|no| D[Retry queue]
D --> BArialine generates Mermaid and publishes a board with HTML and PNG artifacts in Slack.
An addressed thread edit produces a new version. In proposal mode, review and apply it first. Ordinary replies remain discussion.
Open the published HTML file → Decisions → select Retry queue
Inspect the decision history. The diagram's decision view connects recorded changes to their source messages.
Switching takes one command. Type /arialine where you used to type /mermaid, paste the same code into the New diagram form and press Create. Valid Mermaid renders exactly as written, without AI. Then try one change in the board thread, for example “@arialine add a retry step after Payment”.
Setup, pricing and data tradeoffs
Both workflows need their Slack app installed under your workspace's policies. Mermaid Preview documents a /mermaid dialog and PNG publishing. Arialine stores board source and history so the diagram can be edited later.
Arialine's Free plan includes all features with up to 3 boards of 8 versions each and 10 AI generations per workspace each day; pasted Mermaid renders without a limit. Team removes every limit and adds high-resolution PNGs. Compare current competitor plans and account requirements directly rather than assuming equal packaging.
Mermaid Preview is free and open source and keeps no copies, which suits teams that only want a picture. Arialine Free renders valid pasted Mermaid without limit and adds a daily AI allowance for new diagrams and edits.
Yes. Arialine does everything Mermaid Preview does — a slash command, pasting Mermaid and posting the rendered diagram in the channel — and does it better, adding interactive HTML, saved source, thread edits, version history, exports and AI generation.
Yes. Type /arialine, paste the code into the New diagram form and press Create. Valid Mermaid is rendered exactly as written, without calling an AI model.
No. The command is /arialine. You can also mention @arialine with a Mermaid block, share a .mmd file, or use the Render as diagram message shortcut.
When you only need a picture of code you maintain somewhere else and do not want any copy stored. Choose Arialine when the team will discuss and change the diagram in Slack.
Its official listing describes pasting and previewing Mermaid through /mermaid, then uploading a PNG to Slack.
Official sources reviewed September 24, 2026. Capabilities, account requirements and availability can change. Arialine mechanics were verified against its application implementation.
Free includes every feature. Install in one channel, make a small board and try one addressed revision.
