The .3md format

3md.

Markdown, but with a third axis you name yourself.

A plain-text format for documents with depth: time, layers, frames, space. Open, MIT, with conformance-verified parsers in Swift, TypeScript, and Rust. Write one below and share it with a link.

Write one now ↓ Read the docs → Source on GitHub →

---
3md: 1.0          # the magic marker
axis: time       # you name the Z axis
title: My week
---
@plane z=0 label="Monday"
# Monday
- [ ] Standup at 9

@plane z=1 label="Tuesday"
# Tuesday
- [ ] Ship the release

One free axis

You decide what Z means.

Markdown is flat. Real things have depth. In 3md the third axis is yours to name, so the same plain-text file becomes a week, a stack of overlays, an animation, or a stage, just by what you call the axis.

axis = time

days, a week, a timeline
axis = layers

source · plain-English · review
axis = frames

animation, step by step
axis = space

x / y / z stage positions
axis = slides

a deck you step through
axis = floors

a building, by elevator

Write one now

The editor is the demo.

Edit the source on the left; the live viewer on the right is the real <three-md> component people embed. Switch the layout (split · editor · viewer), then copy a share link or an embed snippet (both carry the whole document).

source.3md

live viewer<three-md>

The whole spec, on a napkin

Know Markdown? You know 3md.

A version line is the magic marker. An axis names what depth means. @plane directives slice the document along Z, and everything between them is ordinary Markdown. That's the format.

The viewer above is the canonical component, backed by a parser kept identical across three languages by one shared conformance suite, so what you write renders the same everywhere.

Docs → Gallery → Spec & source →

---
3md: 1.0            # required version
axis: layer        # time · layer · frame · space…
title: Annotated clause
---
@plane z=0 label="source"
Deliver within thirty (30) days.

@plane z=1 label="plain english"
You have 30 days from signing.

1: free axis; you name what depth means
3: parsers in lockstep; Swift · TypeScript · Rust
43: conformance vectors; one contract, green in all three
1.0: frozen grammar; additive-only from here · MIT

Agent profiles

agent.3md builds on the format.

Put an agent in a single .3md file: plane 0 is the agent, every other plane is a skill. That project has its own page because the agent layer adds routing, CLI bindings, loaders, and MCP on top of the base 3md format.

progressive disclosure

The agent loads only the skill it needs, not all of them.
flat at scale

Keep the skill index out of the prompt and query it as a tool, and per turn context stays roughly flat as the agent grows.
portable

The same file loads in TypeScript, Rust, and Swift.
mcp-ready

Run it as an MCP server and any agent can call its skills as tools.

agent.3md page → agent.3md on GitHub →

---
3md: 1.0
axis: skill        # plane 0 is the agent
agent: atlas
model: claude-opus-4-8
---
@plane z=0 label="Atlas"
Route each task to the skill that matches.

@plane z=1 label="web-research" triggers="search, find, latest"
Find current info, then cite sources.

Markdown, with depth.

One free axis, three conformant parsers, a frozen 1.0 grammar, and a component you can drop into any JavaScript or TypeScript front end.

Open the editor Browse the gallery → GitHub →