Markdown cheat sheet

Updated April 26, 2026 · 8 min reference · by Samuel Yoo

Every Markdown syntax you’ll need, side by side with the rendered output. This page covers CommonMark (the standard) plus GitHub-Flavored Markdown (GFM) extensions — the same dialect rendered by GitHub, the viewer, and most modern Markdown processors.

For interactive testing, paste any of these examples into the viewer and watch them render.

Headings

# H1 — page title
## H2 — section
### H3 — subsection
#### H4
##### H5
###### H6

Use a single H1 per page. Skipping levels (H1 → H3) hurts readability and SEO; go through each level in order.

Don’t: add # characters with no space — #heading is a tag, not a heading.

Paragraphs and line breaks

First paragraph.

Second paragraph — a blank line separates them.

A line break in a single paragraph requires
two trailing spaces, or an explicit \  backslash.

In GFM (GitHub’s flavor), a single newline becomes a <br> automatically — no trailing spaces needed. The viewer follows GFM behavior.

Emphasis

**bold** or __bold__
*italic* or _italic_
***bold italic***
~~strikethrough~~  (GFM)

Convention: use * and _ consistently. Some teams prefer **bold** (asterisks) for bold and _italic_ (underscores) for italic to make the distinction visually obvious.

Lists

Unordered

- Item one
- Item two
  - Nested (2-space indent)
- Item three

Ordered

1. First
2. Second
3. Third

The numbers don’t have to be sequential — Markdown auto-numbers them. Many authors write 1. for every line and let the renderer count.

Task lists (GFM)

- [x] Done
- [ ] Pending
- [ ] Also pending

Renders as checkboxes; usable as a TODO format in READMEs and issues.

Links

[Inline link](https://tooljo.com)
[Title attribute](https://tooljo.com "tooljo home")

<https://tooljo.com>          ← autolink
https://tooljo.com            ← autolink (GFM)

[Reference link][ref]
[Implicit reference][]

[ref]: https://tooljo.com
[Implicit reference]: https://tooljo.com

For long links repeated multiple times, reference-style keeps the prose clean. The reference definitions can go anywhere in the document.

Images

![Alt text](https://example.com/image.png)
![Alt text](image.png "Optional title")
[![Linked image](image.png)](https://example.com)

Always include alt text — it’s the SEO and accessibility signal. Reference-style works for images too:

![Logo][logo]

[logo]: assets/logo.svg "Company logo"

Code

Inline

Use the `format` function — backticks make code spans.

Fenced blocks

```js
function greet(name) {
  return `Hello, ${name}!`;
}
```

The language hint (js, python, rust, bash, etc.) enables syntax highlighting in renderers that support it. GitHub recognizes 600+ languages; most renderers know the popular dozen.

Indented blocks (legacy)

    Indented 4 spaces.
    Becomes a code block.

Avoid in new content — fenced blocks are clearer and let you specify a language.

Blockquotes

> A single-line quote.

> A multi-line quote.
> Continued on the next line.
>
> > Nested quote (use multiple `>`).

Tables (GFM)

| Column | Type | Notes |
|---|---|---|
| id | uuid | primary key |
| email | text | unique |

| Left | Center | Right |
|:-----|:------:|------:|
| L | C | R |

The : in the divider row sets alignment. Cells don’t have to line up visually in the source — the renderer normalizes them.

Horizontal rule

---
***
___

Three of any of these on their own line. --- is most common.

Escaping

Use \ to escape a Markdown character:

\*not italic\*
\# not a heading
\[not a link\](nowhere)

Inside code spans and code blocks, no escaping needed — content is verbatim.

Footnotes (GFM)

Here's a claim[^1] and another[^longer-name].

[^1]: First footnote.
[^longer-name]: A footnote with a more readable identifier.

Renders as superscript references with a list at the bottom.

HTML embeds

Markdown lets you embed raw HTML. Common useful cases:

<details>
  <summary>Click to expand</summary>
  Hidden content here.
</details>

<kbd>Cmd</kbd>+<kbd>K</kbd>

<sub>subscript</sub> and <sup>superscript</sup>

The viewer sanitizes the rendered HTML, so embedded <script> or event handlers are stripped — safe to render untrusted markdown.

Front matter (extension, not standard)

Many static-site generators (Jekyll, Hugo, Astro, Gatsby) support YAML or TOML front matter at the top of a Markdown file:

---
title: Hello
date: 2026-04-26
tags: [intro, demo]
---

# Hello world

This is not part of CommonMark or GFM. Renderers that don’t support it show the front matter as a literal --- rule and a list. Strip it before pasting into a generic Markdown viewer.

What’s NOT in standard Markdown

These are common requests that need extensions or a non-standard flavor:

When you need these, either embed HTML directly or pick a flavor that supports them (Pandoc Markdown, MultiMarkdown, AsciiDoc).

Rendering targets

The same Markdown source renders slightly differently across:

• GitHub — GFM with their internal CSS. The de facto reference.
• GitLab — GFM-compatible, plus extras (math via KaTeX, Mermaid native).
• Reddit — a heavily restricted subset.
• Discord — GFM-ish with Discord-specific timestamps and mentions.
• VS Code — preview pane uses markdown-it; supports GFM by default.
• Static site generators (Hugo, Jekyll, Astro, Gatsby) — usually GFM via a parser like Goldmark or marked.
• md.tooljo.com ← this site, GFM via marked + DOMPurify.

If a snippet renders fine here but not on the target platform, the issue is almost always (a) a non-standard extension or (b) the platform’s sanitization stripping HTML.

Syntax to memorize first

If you only learn five things:

1. # H1, ## H2 for structure.
2. **bold**, *italic* for emphasis.
3. - item for lists.
4. [text](url) for links.
5. ``` (triple backticks) for code blocks.

Everything else, look up here as needed.

Try it

• Markdown viewer — paste any of these examples and watch them render
• Markdown → HTML — copy clean HTML output
• HTML → Markdown — reverse direction
• What is Markdown? — background