How to Italicize Text in Markdown

The quick answer: Wrap text with single asterisks — italic text — to make it italic. This works universally across GitHub, Obsidian, Notion, Discord, and all CommonMark-compliant renderers.

Basic Syntax

Two syntaxes produce italic text in markdown:

• italic text — single asterisk (recommended)
• _italic text_ — single underscore

Both render visually identical output. However, single asterisks are the universally safer choice. Underscores have an important limitation: they can fail mid-word on many parsers.

Why Underscores Sometimes Fail

The CommonMark specification requires that underscore-delimited emphasis cannot open or close inside a word. This is intentional — many English words contain underscores in technical contexts (like variable_name) and treating every underscore as italic would cause chaos.

This works: _entire phrase italicized_

This does NOT work on most parsers: _un_natural (attempting to italicize "un" inside a word)

Asterisks don't have this restriction, which is why they're the preferred choice.

Combining Italic with Other Formatting

Bold + Italic

Use three asterisks for bold italic: bold and italic text

Nested Emphasis

You can nest italic inside bold: This is bold with some italic inside

Or bold inside italic: This is italic with some bold inside

Italic Inside Other Elements

Italic works inside headings, blockquotes, list items, and table cells: ## Italic heading > Italic text inside a blockquote - List item with italic word

Platform-by-Platform Breakdown

GitHub and GitLab

Both asterisk and _underscore_ work for italic. GitHub follows the CommonMark spec strictly, so mid-word underscores don't italicize — use asterisks for safety.

Obsidian

Full support for both syntaxes. Obsidian's editor highlights italic text in the source view so you can see formatting at a glance.

Notion

Notion supports both text and _text_ in its markdown import mode. In the Notion editor UI, use Ctrl+I / Cmd+I. Exported markdown from Notion uses asterisks.

Discord

Discord supports italic with single asterisks. Underscores also work in Discord. There is no rendering difference between the two.

Slack

Slack uses its own mrkdwn format, which diverges from standard markdown:

• Slack uses _underscore_ for italic — not asterisk
• Asterisks in Slack create bold text

This is a frequent source of confusion when copying markdown between platforms. Always check whether you're targeting Slack or a standard markdown renderer.

Common Mistakes

Spaces Inside Asterisks

text — wrong: spaces inside the asterisks prevent rendering text — correct: asterisks touch the text directly

Mismatched Delimiters

*italic_ — wrong: opening and closing delimiters must match italic — correct

Mid-Word Underscores

_un_natural — won't render italic on GitHub or most CommonMark parsers unnatural — asterisk version does work mid-word (though unusual)

Forgetting to Close

*italic text — the opening asterisk without a matching closing asterisk will render as a literal asterisk character, not italic.

Real-World Use Cases

Technical Documentation

When introducing a new technical term, italicize it on first use: "The idempotency key ensures that duplicate requests don't create duplicate results." This is a documentation convention borrowed from academic writing.

AI-Generated Content

When you export content from ChatGPT or Claude, italic is often used for book titles, technical concepts, and nuanced emphasis. Paste into MarkdownTools and the preview will show you exactly how the italic renders before you export to PDF.

Markdown in Git Commits

Italic is less useful in Git commit messages (which are plain text), but in GitHub issue and PR descriptions, italic works well for quoting variable names or file paths: The config.json file was renamed to settings.json.

Study Notes in Obsidian

Obsidian users frequently italicize vocabulary terms, foreign words, and first-mention concepts in their knowledge base notes — matching academic citation style.

Italic vs Bold: When to Use Which

Bold is for high-urgency emphasis — things the reader must notice. Use it for warnings, key terms that define the document's core idea, and critical action items. Italic is for soft emphasis — things the reader should notice but that aren't urgent. Use it for titles, introduced terms, and nuance. Both together (bold italic) should be extremely rare — reserved for the most critical warnings in technical documentation.

A practical rule: if you'd highlight it with a physical highlighter on paper, use bold. If you'd read it with a slight emphasis in your head but wouldn't stop someone to point it out, use italic.

Tips for AI-Generated Content

AI models like ChatGPT and Claude frequently use italic for:

• Titles of documents, books, and software
• Introducing technical vocabulary
• Quoting a concept being discussed abstractly ("the notion of emergence in complex systems")

When cleaning up AI-generated markdown, italic is usually correct as-is. The main thing to watch for is whether the output targeted Slack (where it'll show literal underscores) or a standard renderer.

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See the Markdown Italic reference for complete syntax details and platform support.

Ready to put this into practice? Paste your markdown into the free MarkdownTools PDF exporter or HTML converter — no signup required.