How to Create ASCII Diagrams for Code Documentation (2026)
Draw boxes, arrows, and flowcharts in plain text for README files, code comments, and pull request descriptions. Free ASCII diagram editor.
- Draw boxes, arrows, and flowcharts in plain text for README files, code comments, and pull request descriptions.
- What Are ASCII Diagrams?.
- When to Use ASCII Art Over Images.
- Covers using the ascii diagram editor.
- Covers common diagram patterns.
What Are ASCII Diagrams?
ASCII diagrams are visual representations made entirely from text characters. They use box-drawing characters (┌─┐│└─┘) for structure, arrows (→ ← ↑ ↓) for flow, and regular text for labels. They've been a staple of software documentation since the 1970s because they render identically in every terminal, editor, and code review tool. Unlike images, they're searchable, diffable, and never break due to missing assets. When you see an architecture diagram in a code comment, a flow description in a README, or a state machine in a pull request, that's ASCII art at work.
When to Use ASCII Art Over Images
Use ASCII diagrams in code comments where images aren't possible. Use them in README.md files where you want the diagram to render without hosting images. Use them in pull request descriptions and commit messages. Use them in CLI tool documentation where users read output in a terminal. Use them in any context where the diagram should be version-controlled alongside code. Don't use ASCII diagrams for complex UML, detailed architecture diagrams with dozens of components, or anything that needs color coding — those deserve a proper diagramming tool.
auto-fill and auto-fit behave differently when there are fewer items than columns. Use auto-fill to keep empty tracks; auto-fit to collapse them.Using the ASCII Diagram Editor
Select the Box tool and drag on the grid to create rectangles with proper box-drawing characters. Switch to the Arrow tool to draw connections between boxes — horizontal and vertical lines with directional arrowheads. The Text tool lets you type labels directly on the grid. The Eraser removes individual characters. When you're done, click Copy to grab the entire diagram as plain text — the export trims trailing whitespace automatically so the output is clean. The grid auto-highlights your drawing area as you work.
width, height, top, or left. These trigger layout recalculations on every frame and can drop performance below 60fps.Common Diagram Patterns
The most common ASCII diagram is a simple box-and-arrow architecture: Client → API → Database. For request/response flows, use bidirectional arrows with labels. For decision trees, use diamond shapes (built from / and characters) or labeled branches. State machines work well with boxes connected by labeled arrows. File tree structures use └── and ├── branch characters. Sequence diagrams alternate vertical bars (│) with horizontal arrows (→) between participants. Keep diagrams under 60 characters wide for readability in code review tools with limited column width.