Side project · 2 min read
Mermaid for Jira
None of the Jira diagram apps worked, so I built a free one with AI in a couple of hours after work.
Free. Your usage counts toward my Atlassian allowance. Not on the Marketplace. Read the source first if you like.
Free Mermaid editor and viewer
free · nothing is saved↑ that's Mermaid: text in, diagram out
We needed diagrams that could live within tickets themselves and be edited at the time of refinement. Simply creating diagrams in Miro or similar and screenshotting didn't cut it.
None of the Marketplace apps worked. I tried several that all claimed they did. Some didn't show up at all after install. The official Mermaid one asked for a login, so I created an account. Only to find out that one doesn't work at all.
So I built my own.
What it is
Mermaid turns text into diagrams. My app puts them in a panel on the Jira issue, right next to the ticket they're about. You write the diagram as text, or click shapes together, and change it there whenever the ticket changes.
It isn't a whiteboard. The text is always the source of truth, and two people can't edit the same diagram live.
Building it
Mermaid styles kept getting blocked. Jira runs apps in a sandbox that doesn't allow inline styles, and that's exactly how Mermaid colours its diagrams. So the app bakes the colours straight into the SVG instead.
Other than that, it surprised me how easy it was to build this with AI. It wasn't even a week, it was a couple of hours after work.
Free, and never on the Marketplace
Ideally I wanted this listed on the Atlassian Marketplace for free. But Atlassian still bills for free apps. Since January 2026 the developer pays for any usage above a monthly free allowance. This one has no server and no database, so it doesn't use much, but the bill for everyone's usage would still land on me, and I wouldn't control who installs it. So it will never be on the Marketplace.
But you can install it in one click. Yes, that's on me too: your usage counts toward my free allowance. The difference is I can switch the link off if it ever gets out of hand. Still not on the Marketplace though.
You need to be an admin of a Jira Cloud site. Or star the repo and register it under your own Atlassian account, so your usage counts against your own allowance. The README has the steps.
What it asks for: permission to read and write issue properties, nothing else. Your diagrams are stored on the Jira issue itself. Their contents aren't sent to my server or any external service. (This demo page loads Mermaid and web fonts from public CDNs.)