Quick Reference

This reference covers CommonMark syntax and GitHub Flavored Markdown (GFM) extensions. Elements marked with "GFM" require GitHub Flavored Markdown support.

Standards Covered:

CommonMark 0.30 (2021)
GitHub Flavored Markdown (2017)

Compatibility:

GitHub, GitLab, Discord, Slack
Most modern Markdown parsers

Headers

H1-H6 Headers

Create hierarchical headers using 1-6 hash symbols

Syntax:

# H1
## H2
### H3
#### H4
##### H5
###### H6

Rendered Output:

H1

H2

H3

H4

H5

H6

Note: Always use a space after the hash. Avoid skipping header levels.

Alternative H1/H2

Alternative syntax for H1 and H2 using underlines

Syntax:

Header 1
========

Header 2
--------

Rendered Output:

Header 1
========

Header 2
--------

Note: Underline must be at least as long as the header text

Text Formatting

Bold Text

Make text bold using double asterisks or underscores

Syntax:

**bold text** or __bold text__

Rendered Output:

bold text or __bold text__

Note: Asterisks are more common and work in more contexts

Italic Text

Make text italic using single asterisks or underscores

Syntax:

*italic text* or _italic text_

Rendered Output:

italic text or _italic text_

Note: Use underscores when asterisks appear in the text

Bold and Italic

Combine bold and italic formatting

Syntax:

***bold and italic*** or ___bold and italic___

Rendered Output:

bold and italic or ___bold and italic___

Note: Can also use **_text_** or __*text*__

Strikethrough

Cross out text (GitHub Flavored Markdown)

Syntax:

~~strikethrough text~~

Rendered Output:

~~strikethrough text~~

Note: Not supported in all Markdown parsers

Inline Code

Format code or technical terms inline

Syntax:

`inline code`

Rendered Output:

inline code

Note: Use double backticks for code containing backticks: ``code with `backticks` ``

Lists

Unordered Lists

Create bullet lists using -, *, or +

Syntax:

- Item 1
- Item 2
  - Nested item
  - Another nested item
- Item 3

Rendered Output:

- Item 1
- Item 2
- Nested item
- Another nested item
- Item 3

Note: Use consistent markers. Indent nested items with 2 spaces

Ordered Lists

Create numbered lists using numbers and periods

Syntax:

1. First item
2. Second item
   1. Nested item
   2. Another nested
3. Third item

Rendered Output:

1. First item
2. Second item
1. Nested item
2. Another nested
3. Third item

Note: Numbers don't need to be sequential. Use 3 spaces for nesting

Task Lists

Create checkboxes (GitHub Flavored Markdown)

Syntax:

- [x] Completed task
- [ ] Incomplete task
- [x] Another completed task

Rendered Output:

- [x] Completed task
- [ ] Incomplete task
- [x] Another completed task

Note: Use [x] for checked, [ ] for unchecked

Links and Images

Inline Links

Create clickable links

Syntax:

[Link text](https://example.com)

Rendered Output:

[Link text](https://example.com)

Note: URLs are automatically linked in many parsers

Links with Titles

Add hover text to links

Syntax:

[Link text](https://example.com "Title text")

Rendered Output:

[Link text](https://example.com "Title text")

Note: Title appears on hover in most browsers

Reference Links

Define links separately for cleaner text

Syntax:

[Link text][1]

[1]: https://example.com

Rendered Output:

[Link text][1]

[1]: https://example.com

Note: Useful for documents with many repeated links

Images

Embed images using exclamation mark before link syntax

Syntax:

![Alt text](image.jpg "Optional title")

Rendered Output:

![Alt text](image.jpg "Optional title")

Note: Alt text is crucial for accessibility

Code Blocks

Fenced Code Blocks

Create code blocks with syntax highlighting

Syntax:

```javascript
function hello() {
  console.log('Hello!');
}
```

Rendered Output:

function hello() {
  console.log('Hello!');
}

Note: Specify language for proper highlighting

Indented Code Blocks

Create code blocks using 4-space indentation

Syntax:

    function hello() {
        console.log('Hello!');
    }

Rendered Output:

function hello() {
console.log('Hello!');
}

Note: No syntax highlighting with this method

Blockquotes

Simple Blockquotes

Create quoted text using >

Syntax:

> This is a blockquote
> spanning multiple lines

Rendered Output:

> This is a blockquote
> spanning multiple lines

Note: Add > to each line or use lazy continuation

Nested Blockquotes

Create nested quotes using multiple >

Syntax:

> Outer quote
> > Nested quote
> Back to outer quote

Rendered Output:

> Outer quote
> > Nested quote
> Back to outer quote

Note: Useful for email-style quote threading

Tables (GFM)

Basic Tables

Create tables using pipes and dashes

Syntax:

| Header 1 | Header 2 | Header 3 |
|----------|----------|----------|
| Cell 1   | Cell 2   | Cell 3   |
| Cell 4   | Cell 5   | Cell 6   |

Rendered Output:

| Header 1 | Header 2 | Header 3 |
|----------|----------|----------|
| Cell 1 | Cell 2 | Cell 3 |
| Cell 4 | Cell 5 | Cell 6 |

Note: Outer pipes are optional. Use at least 3 dashes for separators

Aligned Tables

Align columns using colons in separator row

Syntax:

| Left | Center | Right |
|:-----|:------:|------:|
| L1   |   C1   |    R1 |
| L2   |   C2   |    R2 |

Rendered Output:

| Left | Center | Right |
|:-----|:------:|------:|
| L1 | C1 | R1 |
| L2 | C2 | R2 |

Note: :--- (left), :---: (center), ---: (right)

Horizontal Rules

Create horizontal dividers

Syntax:

---
or
***
or
___

Rendered Output:

---
or
***
or
___

Note: Use at least 3 characters. Can have spaces between

Escaping

Escape Characters

Escape special characters with backslashes

Syntax:

\* Not italic \*
\# Not a header

Rendered Output:

\ Not italic \
\# Not a header

Note: Use \ before: \ ` * _ { } [ ] ( ) # + - . !

Common Mistakes and Solutions

❌ Common Mistakes

Missing spaces: Using #Header instead of # Header
Inconsistent indentation: Mixing tabs and spaces in lists
Incorrect nesting: Using wrong number of spaces for nested items
Unescaped characters: Using * or _ without escaping when not formatting
Missing blank lines: Not separating elements with blank lines

✅ Best Practices

Consistent spacing: Always use spaces after # for headers
Proper nesting: Use 2 spaces for unordered lists, 3 for ordered
Blank line separation: Add blank lines around headers, lists, and code blocks
Meaningful alt text: Always include descriptive alt text for images
Language specification: Always specify language for code blocks

Feature Compatibility

Feature	CommonMark	GitHub	Discord	Slack	Reddit
Headers	✅	✅	✅	✅	✅
Bold/Italic	✅	✅	✅	✅	✅
Strikethrough	❌	✅	✅	✅	✅
Tables	❌	✅	✅	❌	✅
Task Lists	❌	✅	❌	❌	❌
Math	❌	✅	❌	❌	❌

Related Resources

Learn More

Tools

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