# Start a diagram

Paste or drop Mermaid you already have, open an example, or start a new blank diagram.

## Paste Mermaid text

Copy Mermaid text from anywhere, open the [diagram page](/diagram) and press **⌘V** (Mac) or **Ctrl+V** (Windows). You can also right-click the diagram and choose **Paste**.

Line9 replaces the diagram on the page with the one you pasted. To go back, click **Undo** in the message that appears.

You can paste a whole chat reply or Markdown document: Line9 uses the first Mermaid diagram in it. Pasting a Line9 link opens the diagram it links to.

## Drop or open a file

Drag a file onto the diagram page, or open the menu in the top-left corner and choose **Diagram ▸ Open from file…**. Line9 opens:

- `.mmd` and `.mermaid` files
- `.md` files that contain a Mermaid diagram

With [Line9 Pro](/docs/getting-started#line9-pro), **Diagram ▸ Open…** finds any diagram your team has published.

## Open an example

Choose **Diagram ▸ Examples** and pick one. The examples are grouped by subject, from business processes to architecture. Line9 opens a copy for you to change.

![The menu open at Diagram, then Examples, which lists Parcel Delivery and seven groups of examples.](/images/docs/screens/start-a-diagram/examples.png)

You can also browse the examples, with their Mermaid text, in the [flowchart examples library](/mermaid).

## Start a new blank diagram

Choose **Diagram ▸ New diagram**, then **Flowchart** or **Sequence diagram**. The text opens on the left, ready for you to type.

With Line9 Pro, a new flowchart opens in the Line9 editor instead. The [editor tutorial](/docs/editor-tutorial) builds one step by step.

## Have an AI draw it

Connect Line9 to ChatGPT, Claude or another chat app, and it draws the diagrams you ask for with Line9. See [Line9 in chat apps](/docs/mcp). Developers using a coding agent, such as Claude Code or Codex, can use the [Line9 CLI](/docs/cli).

Without Line9 connected, ask the AI for a Mermaid flowchart, then paste its reply onto the diagram page.

## Keep your diagram

Line9 keeps your latest diagram in this browser and opens it again when you come back. Opening or starting another diagram replaces it.

To keep a diagram, copy a link, export it or publish it. See [Share a link, image or text](/docs/share).

## Two diagram types: flowcharts and sequence diagrams

Line9 lays out two types of Mermaid diagram.

A **flowchart** shows the steps of a process and the decisions between them.

![The expense approval flowchart, from the employee's claim, through approval, to payment.](/images/docs/diagrams/expense-approval.svg)

A **sequence diagram** shows who sends what to whom, in order.

![A sequence diagram of an expense claim passing between the employee, the expenses app, the line manager and Finance.](/images/docs/diagrams/expense-claim-sequence.svg)

Line9 opens other types of Mermaid diagram too, such as pie charts and Gantt charts. Mermaid draws these, and the diagram page shows a **Mermaid** label at the top.

## Diagram size limit

Line9 lays out diagrams of up to 100 nodes. Mermaid draws a larger diagram instead, with the same **Mermaid** label. A diagram that size is hard to read, so you may want to split it into several smaller ones.

## Next

- [Edit the diagram's text](/docs/diagram-text): how Mermaid text describes a diagram.
- [Nodes, edges and groups](/docs/nodes-edges-and-groups): the parts a flowchart is made of.
- [Line9 in chat apps](/docs/mcp): have ChatGPT or Claude draw diagrams with Line9.