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GitHub Markdown Guide

Every GitHub Flavored Markdown feature in one place. 30+ features with copy-paste syntax and live previews.

30+ featuresGFM compliantUpdated 2026Free forever

Quick Reference

All GitHub markdown syntax at a glance.

Feature	Syntax	Notes
Bold	`text`	Double asterisks
Italic	`text`	Single asterisks or underscores
Bold Italic	`*text*`	Triple asterisks
Strikethrough	`~~text~~`	Double tildes (GFM)
Subscript	`<sub>text</sub>`	HTML sub tag
Superscript	`<sup>text</sup>`	HTML sup tag
Heading	`# H1 ... ###### H6`	Hash + space
Inline Link	`[text](url)`	Square brackets + parentheses
Reference Link	`[text][id]`	Define [id]: url elsewhere
Autolink	`https://...`	Bare URLs auto-link in GFM
Inline Code	`code`	Single backticks
Code Block	```\ncode\n```	Triple backticks
Syntax Highlight	```js\ncode\n```	Language after backticks
Unordered List	`- item`	Dash, asterisk, or plus
Ordered List	`1. item`	Number + period
Task List	`- [ ] todo`	Interactive checkboxes (GFM)
Blockquote	`> text`	Greater-than sign
Alert	`> [!NOTE]`	NOTE, TIP, WARNING, CAUTION, IMPORTANT
Table	`\| a \| b \|`	Pipes + header separator row
Image	`![alt](url)`	Exclamation + link syntax
Footnote	`[^1]`	Define [^1]: text at bottom
Details	`<details>...</details>`	Collapsible sections
Mermaid	```mermaid\n...\n```	Diagrams rendered natively

Text Formatting

GitHub supports 6 inline text styles including GFM strikethrough and HTML sub/superscript.

Bold

Make text bold with double asterisks

README.md

bold text

Italic

Emphasize text with single asterisks

README.md

italic text

Bold Italic

Combine bold and italic

README.md

bold italic text

Strikethrough

Cross out text (GFM extension)

README.md

~~strikethrough text~~

Subscript

Subscript text using HTML

README.md

H₂O

Superscript

Superscript text using HTML

README.md

x² + y²

Headings & Links

Six heading levels and three link formats including GFM autolinks.

Headings

Six levels from H1 (largest) to H6 (smallest)

README.md

Heading 1

Heading 2

Heading 3

Heading 4

Inline Link

Link with custom display text

README.md

GitHub

Reference Link

Define URLs separately for cleaner source

README.md

GitHub

Autolink

Bare URLs become clickable automatically (GFM)

README.md

https://github.com

Code

Inline code, fenced code blocks, and syntax highlighting for 500+ languages.

Inline Code

Highlight code within a sentence

README.md

git status

Fenced Code Block

Multi-line code with triple backticks

README.md

const hello = 'world'\nconsole.log(hello)

Syntax Highlighting

Add language name for colored highlighting

README.md

def greet(name):\n    return f"Hello, {name}!"

Lists

Unordered, ordered, nested, and interactive task lists.

Unordered List

Bullet points with dashes, asterisks, or plus signs

README.md

First item
Second item
Third item

Ordered List

Numbered list items

README.md

First item
Second item
Third item

Nested List

Indent with 2 spaces for sub-items

README.md

Parent item
- Child item
- Child item
Another parent

Task List

Interactive checkboxes (GFM extension)

README.md

☑ Write the code
☑ Run the tests
☐ Update docs

Blockquotes & Alerts

Standard blockquotes plus GitHub's five colored alert callout types.

Blockquote

Quote text with greater-than sign

README.md

This is a blockquote

Nested Blockquote

Multiple levels of quoting

README.md

First level
Nested quote
Deeply nested

Alert — Note & Tip

Informational and helpful callouts

README.md

ℹ️ Note
Useful information that users should know.

💡 Tip
Helpful advice for doing things better.

Alert — Warning, Caution & Important

Urgency and critical information callouts

README.md

⚠️ Warning
Urgent info that needs immediate attention.

🛑 Caution
Negative potential consequences of an action.

💬 Important
Key information users need to know.

Tables

GitHub Flavored Markdown tables with alignment and formatted content.

Basic Table

Pipes for columns, hyphens for header separator

README.md

Feature	Status
Bold	✅ Supported
Tables	✅ Supported

Column Alignment

Use colons in the separator row

README.md

Left	Center	Right
A	B	C
D	E	F

Formatted Table Content

Use inline formatting inside table cells

README.md

Feature	Syntax
Bold	`text`
Italic	`text`

Media & References

Images, footnotes, and anchor links for navigation within documents.

Image

Embed images with alt text

README.md

[Image: Screenshot of app]

Footnote

Add references that appear at the bottom

README.md

Here is a statement¹.

This is the footnote content. ↩

Anchor Link

Link to a heading within the same document

README.md

Installation

...
Back to top

GitHub-Specific Features

Collapsible sections, mermaid diagrams, and relative file links — unique to GitHub.

Collapsible Section

Expandable content with <details> tag

README.md

Click to expand

Hidden content goes here.

Item 1
Item 2

Mermaid Diagram

Render diagrams natively in GitHub

README.md

Start→Decision→Do it

Rendered as interactive SVG on GitHub

Relative File Link

Link to files within the same repository

README.md

Read the docs
See the source

Unsupported in GitHub Markdown

Standard features that GitHub strips or does not render.

Underline

No native underline syntax — <u> tags are stripped in most contexts

Embedded Videos

Use linked thumbnail images or GitHub's video upload instead

Custom CSS

GitHub sanitizes all style attributes and <style> tags

Colored Text

No <font> or style-based color support — use diff code blocks for green/red

Pro Tips

1Keyboard Shortcuts in Issues/PRs

Press Cmd/Ctrl+B for bold, Cmd/Ctrl+I for italic, and Cmd/Ctrl+K to insert a link. GitHub's web editor has built-in markdown toolbar buttons too.

2Drag-and-Drop Images

Drag images directly into any GitHub text area (issues, PRs, comments). GitHub uploads them automatically and inserts the markdown image syntax for you.

3Reference Issues and PRs

Type # followed by a number to reference issues/PRs (e.g., #123). Use owner/repo#123 for cross-repository references. These automatically become clickable links.

Fixes #42
See also org/repo#100

4@Mention Users and Teams

Use @username to mention a person or @org/team to mention an entire team. They'll receive a notification and the mention becomes a link to their profile.

5Diff Syntax Highlighting

Use the "diff" language in code blocks to highlight additions (green) and deletions (red). Prefix lines with + or - to mark changes.

```diff
- old line removed
+ new line added
  unchanged line
```

6Permalink to Code

Click a line number on any GitHub file, then press Y to get a permanent link to that exact version. Paste the URL in markdown and GitHub renders it as an embedded code snippet.

Frequently asked questions

Everything you need to know.

What is GitHub Flavored Markdown (GFM)?

GitHub Flavored Markdown (GFM) is GitHub's extended version of standard markdown (CommonMark). It adds tables, task lists, strikethrough, autolinks, and alert callouts on top of the standard syntax. GFM is used in READMEs, issues, pull requests, comments, wikis, and discussions.

What is GitHub Flavored Markdown (GFM)?

How do I create a table in GitHub markdown?

Use pipes (|) to separate columns and hyphens (-) for the header separator row. Example: | Name | Value | on the first line, | --- | --- | on the second, then your data rows. Use colons for alignment: :--- (left), :---: (center), ---: (right).

How do GitHub markdown alerts work?

GitHub supports five alert types using blockquote syntax: > [!NOTE], > [!TIP], > [!IMPORTANT], > [!WARNING], and > [!CAUTION]. Each renders with a distinct color and icon. Place the alert marker on its own line inside a blockquote, then add your content on the following lines.

Does GitHub markdown support mermaid diagrams?

Yes. GitHub natively renders mermaid diagrams inside fenced code blocks with the "mermaid" language identifier. Supported diagram types include flowcharts, sequence diagrams, class diagrams, Gantt charts, pie charts, and more. The diagrams render as SVGs directly in your markdown.

How do task lists (checkboxes) work on GitHub?

Use - [ ] for an unchecked item and - [x] for a checked item. In issues and pull requests, task lists are interactive — you can click the checkboxes to toggle them. GitHub also shows a progress bar when an issue contains task lists.

Can I use HTML in GitHub markdown?

GitHub allows a subset of HTML tags in markdown: <details>, <summary>, <sub>, <sup>, <br>, <hr>, <kbd>, <picture>, <source>, and a few others. Most styling attributes and <script>/<style> tags are stripped for security. The <details> tag is especially useful for collapsible sections.

How do footnotes work in GitHub markdown?

Add a footnote reference in your text with [^1] and define it anywhere in the document with [^1]: Your footnote text. GitHub automatically numbers footnotes and places them at the bottom of the rendered page with backlinks. Footnote identifiers can also be words: [^note].

What programming languages does GitHub syntax highlighting support?

GitHub uses Linguist for syntax highlighting and supports 500+ languages. Common ones include javascript, typescript, python, ruby, go, rust, java, c, cpp, csharp, swift, kotlin, bash, sql, html, css, json, yaml, and markdown. Use the language name or alias after the opening triple backticks.

How do I link to a specific heading in GitHub markdown?

GitHub auto-generates anchor IDs for every heading by lowercasing the text and replacing spaces with hyphens. Link to them with [Link text](#heading-text). For example, ## Getting Started becomes #getting-started. Special characters are removed and duplicates get a -1, -2 suffix.

What is the difference between GitHub markdown and standard markdown?

Standard markdown (CommonMark) covers the basics: headings, bold, italic, links, images, code, lists, and blockquotes. GitHub Flavored Markdown adds tables, task lists, strikethrough (~~text~~), autolinks, footnotes, alert callouts, mermaid diagrams, and math expressions (LaTeX). GFM also allows certain HTML tags.

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