Markdown Cheat Sheet — Every Common Syntax with Examples

Markdown is a lightweight markup language created by John Gruber in 2004. The idea: plain text that already looks readable in an email client compiles to clean HTML. CommonMark (2014) standardised the core; GitHub Flavored Markdown (GFM) adds tables, task lists, and autolinks. This guide pulls the syntax you'll actually use from both.

Headings

# H1 (page title — exactly one per page)
## H2 (section)
### H3 (subsection)
#### H4
##### H5
###### H6

There's a Setext alternative — === below text for H1, --- for H2 — but every modern tool supports atx (#), so prefer that.

Inline styling

**bold** or __bold__
*italic* or _italic_
~~strikethrough~~
`inline code`
==highlight== (some processors only)

Putting i*tal*ic in the middle of a word trips some parsers. Split with spaces or apply only to whole words.

Lists

- unordered (-, *, + all work)
- second item
  - nest with 2 spaces of indent
    - deeper

1. ordered
2. auto-numbered
3. write any number — renumbered from 1
   1. nest with 3 spaces (or a tab)

For nesting, use 2 or 4 spaces. Tabs behave differently across parsers.

Links and images

[label](https://example.com)
[label](https://example.com "tooltip")

Autolink: <https://example.com>

Reference style:
This is a [Markdown][1] document.

[1]: https://daringfireball.net/projects/markdown/

Image: ![alt text](image.png)
Image + link: [![alt](image.png)](https://example.com)

Reference style keeps the prose clean — long URLs don't interrupt sentences. Reuse a single ID for repeated links.

Code blocks

Inline `code` uses single backticks.

```
Fenced block. No language.
```

```javascript
// language hint — syntax highlighting
const x = 42;
```

Or use 4-space indent:
    function foo() {
      return 42;
    }

To include backticks inside a fence, use four backticks for the outer fence or switch to ~~~ (tildes).

Blockquotes

> A single-line quote.
>
> Blank `>` separates paragraphs.
>
> > Nested quote.

> Use **bold**, *italic*, `code` inside quotes.
> Lists work too:
>
> - item 1
> - item 2

Tables (GFM)

| Left | Center | Right |
|:---|:---:|---:|
| A | B | C |
| 1 | 2 | 3 |

The colons in the separator row set alignment — :--- left, :---: center, ---: right. Aligning the pipes visually helps readability but parsers don't require it.

For line breaks inside a cell, use <br>. A real newline breaks the table. For anything complex, drop to raw HTML <table>.

Task lists (GFM)

- [ ] unchecked
- [x] checked
- [ ] nestable
  - [x] sub-item checked

Heavily used in GitHub Issues, PRs, and READMEs. [ ] / [x] inside a list.

Footnotes (extension)

Footnotes[^1] live at the bottom of the page.

[^1]: The footnote body. Aggregated automatically.

Not part of CommonMark, but supported by GFM, Pandoc, MkDocs, and others. Handy for citations.

Horizontal rule

---  (three dashes)
***  (three asterisks)
___  (three underscores)

All equivalent; --- is the convention.

Line breaks and paragraphs

The classic Markdown gotcha — a blank line separates paragraphs; plain newlines are squashed.

First line.
Same paragraph (newline ignored).

A blank line = new paragraph.

Two trailing spaces at end of line
=> hard line break (<br>)

Trailing spaces are invisible and easy to lose. Some parsers also accept \ (backslash + newline) as a hard break.

Embedded HTML

Most Markdown processors pass HTML through.

<details>
<summary>Collapsible section</summary>

You can still use **Markdown** inside.

</details>

<sub>subscript</sub> or <sup>superscript</sup>

Some sandboxed environments (GitHub README) strip out script and iframe tags for security.

Escaping

Prefix a special character with \ to render it literally.

\* literal asterisk
\# avoid a heading
\_ literal underscore
\` literal backtick

Emoji and mentions (GFM)

:rocket: :tada: :white_check_mark:
@username  ← mention (GitHub etc.)
#123       ← issue reference

Conversion tools

Iterating with a live preview is the fastest way to learn — Markdown Preview renders as you type and sanitizes with DOMPurify against XSS. Moving an existing HTML page to Markdown? HTML → Markdown converts headings, lists, links, code, and tables automatically.

Common gotchas

• Merged lists — two adjacent lists without a blank line between them combine. Separate with one blank line.
• Pipes inside table cells — escape as \|.
• List indentation — 2 spaces work in some parsers but fail in others. 4 spaces is the safest.
• Triple backticks inside a code block — use a four-backtick fence or switch to ~~~.

Summary

• Headings #, bold **, italic *, code `.
• Lists with - / 1.; nest by indenting (2 or 4 spaces).
• Links [text](url), images ![alt](url).
• Fenced code blocks with ``` plus a language hint. Tables and task lists are GFM extras.
• Two newlines = new paragraph. Single newlines are ignored.