Edit a Mermaid diagram together
Shared Mermaid is a small collaborative editor for Mermaid text. One diagram source sits beside the Room, every participant edits that same source, and each browser renders the diagram locally as the text changes. You can start from a Flowchart, Sequence, State or ER starter and then rewrite it into whatever the conversation needs.
Quick facts
- Price
- Free; no account or signup
- Shared state
- One Mermaid source string
- Starter templates
- Flowchart, Sequence, State, ER
- Preview
- Rendered locally in each browser
- Source limit
- 12 KiB
- File export
- No download; Copy source instead
How it works
- Open Shared Mermaid in the Room and pick a starter template, or paste Mermaid text straight into the editor.
- Edit the source. The preview redraws as you type, and the Room receives the change once your typing settles.
- Talk it through in Room voice or chat while everybody watches the same diagram update.
- Use Copy source to take the finished Mermaid text into your repository, documentation or issue tracker.
What you can do
- Edit one shared Mermaid source with live local preview.
- Start from Flowchart, Sequence, State or ER starter templates.
- See the last version that parsed stay on screen when new text does not parse.
- Keep editing while somebody else is editing, with a genuine conflict reported rather than silently merged.
- Copy the Mermaid source out at any time.
Why use it in a Free4Chat Room
It is the tool for the moment when a sentence stops being enough: drawing a request flow, sketching the states a thing moves through, or agreeing on how two services talk to each other. Because the editor is in the Room, the diagram and the discussion about it are in the same place, and a correction can be made by the person who spotted it rather than being described to whoever owns the file.
Limits & privacy
The picture never leaves the browser. Only the Mermaid source travels between participants, and each browser renders it locally, so there is no rendering service, no image upload and no arbitrary HTML. Text that does not parse is reported beside the preview and the last version that did parse stays on screen instead of being replaced. Nothing is stored: no account, no document history, no multiple documents, and no file download, so Copy source is how you take the finished diagram away.
Frequently asked questions
Can I download the diagram as a PNG or SVG?
No. The Room sandbox does not grant file downloads, so there is no Download button and no image export in this App. Copy source gives you the Mermaid text, which you can paste into any tool that renders Mermaid and export the image there.
Does the picture get uploaded anywhere?
No. Only the Mermaid source text is shared between the people in the Room, and each browser renders that text itself. There is no rendering service, no image upload and no external diagram service involved.
What happens if I type Mermaid that does not parse?
The error is reported next to the preview and the last version that did parse stays on screen, so a half-finished edit never destroys the diagram the Room is looking at. Fixing the text and getting a valid render again is what clears it.
What if two people edit at the same time?
One of those versions becomes the Room's diagram on every browser, and the other is not silently thrown away. The browser that kept the losing text is told whose version the Room kept and is offered a one-click way to use it, so a real conflict is visible rather than merged character by character.
Is there a history of the diagram?
No. There is one diagram, no versions, no undo history across participants and no permanent document. If you need the result later, copy the source before the Room ends.
Can I paste arbitrary HTML into a label?
No. Labels are rendered as SVG text with Mermaid's strict security level, so diagram content never becomes an HTML subtree, and the text size and edge count are bounded so one large paste cannot hang the Room.