Bold and Italic in Markdown: Complete Emphasis Guide

Using bold and italic in markdown is one of the first things every writer learns, and for good reason: emphasis is how you signal importance, introduce terminology, and guide a reader’s attention through a document. Markdown handles emphasis through simple punctuation wrapping, with multiple syntax options for each style. This guide covers every emphasis type available in standard and extended markdown, with practical notes on when to use each one.

Quick Answer: In markdown, **text** produces bold, *text* produces italic, and ***text*** produces bold italic. Prefer asterisks over underscores for consistency. The CommonMark spec, which over 95% of markdown tools follow, explicitly defines how these 3 emphasis markers interact, including strikethrough (~~text~~) in extended flavors like GitHub Flavored Markdown.

How Do You Make Text Bold in Markdown?

Bold text is produced by wrapping a word or phrase in double asterisks or double underscores:

**This text is bold**
__This text is also bold__

Both render identically. The convention in most style guides and codebases is to prefer double asterisks (**) because they are less ambiguous than underscores in certain edge cases (more on that below).

Bold is appropriate for:

• Key terms being defined or introduced
• Critical warnings or important notes
• Labels in a list of items with descriptions
• The first occurrence of a proper noun in technical documentation

Do not bold text just to add visual variety. Every bolded phrase signals to the reader “this is important.” If everything is bold, nothing is.

How Do You Make Text Italic in Markdown?

Italic uses single asterisks or single underscores:

*This text is italic*
_This text is also italic_

Italics are conventionally used for:

• Titles of works (books, films, albums, software)
• Foreign language words or phrases
• Technical terms on first use (as an alternative to bold)
• Gentle emphasis, less urgent than bold

The book *The Elements of Style* is worth reading.
The Latin phrase *per diem* means "per day."
This process is called *lazy evaluation*.

How Do You Combine Bold and Italic in Markdown?

To apply both bold and italic simultaneously, use triple asterisks or a combination of asterisks and underscores:

***This text is bold and italic***
**_This is also bold and italic_**
*__This is also bold and italic__*

All three approaches render the same way. Triple asterisks (***) are the most explicit and widely supported option.

Use bold-italic sparingly. It carries the highest visual weight and should be reserved for genuinely critical information, warnings, or the most important terms in a document.

How Does Strikethrough Work in Markdown?

Strikethrough wraps text in double tildes and is available in most extended markdown processors (GitHub Flavored Markdown, many editors):

~~This text is crossed out~~

Common uses for strikethrough:

• Showing outdated or deprecated information that still needs to be visible for context
• Demonstrating a correction (“The price was $50 $40”)
• Completed items in a prose list (as opposed to task list checkboxes)
• Showing a “before” state in a comparison

Note that strikethrough (~~) is not part of the original CommonMark specification and may not render in all environments. GitHub Flavored Markdown supports it, which means it works across all GitHub repositories, pull requests, and wikis. GitHub Flavored Markdown is used by over 100 million developers worldwide, making strikethrough one of the most widely encountered extended syntax features. If you need it to work in a specific platform, test it first. For a complete reference of what GFM adds beyond standard markdown, see the GitHub Flavored Markdown guide.

Is There Underline Syntax in Markdown?

Standard markdown has no underline syntax. Underlining was intentionally omitted because underlined text is visually associated with hyperlinks on the web, and using it for emphasis causes confusion.

If you genuinely need underlined text (for example, in legal documents or academic formatting), you can use inline HTML:

<u>This text is underlined</u>

This works in most markdown renderers, but use it with care. Underlined non-link text creates an accessibility issue: users who rely on visual cues to identify links may click underlined text expecting navigation and get nothing.

A better alternative is almost always bold or italic, depending on the type of emphasis you need.

Does Markdown Support Text Highlighting?

Some markdown processors support text highlighting with double equals signs:

==This text is highlighted==

This renders as text with a yellow background highlight (similar to a physical highlighter pen). It is supported in tools like Obsidian, Typora, and some static site generators, but is not part of CommonMark or GitHub Flavored Markdown.

If your target environment supports it, highlight is useful for:

• Marking key passages in notes
• Drawing attention to specific values in technical documentation
• “Spoiler” text that should stand out visually

Check your renderer’s documentation before relying on highlight syntax in documents you plan to share across multiple platforms. Highlight, along with subscript, superscript, definition lists, and other non-standard features, is covered in the markdown extended syntax guide.

Asterisks vs. Underscores: Which Should You Use for Emphasis?

Both * and _ work for bold and italic, so why does convention favor asterisks?

The key difference is how parsers handle emphasis within words. The CommonMark specification explicitly states that underscore-based emphasis does not work mid-word, while asterisk-based emphasis does:

un*believ*able    --> un<em>believ</em>able  (works)
un_believ_able    --> un_believ_able          (does not work in strict parsers)

For whole-word emphasis, both work fine. But for consistency and to avoid surprises, the community standard is to use asterisks for *italic* and **bold**, and reserve underscores for contexts where you need a visual distinction.

The markdown cheat sheet shows both options side by side for quick reference.

How Do You Nest Emphasis in Markdown?

You can nest different types of emphasis, but the syntax needs to close in the correct order (innermost first):

You can combine **bold with *italic* inside it**.

Renders as: You can combine bold with italic inside it.

Mismatched nesting (opening with **, then *, then closing ** before *) will not render correctly in strict parsers. Always close the innermost tag first.

Can Emphasis Span Multiple Words and Paragraphs?

Emphasis can span multiple words, but not multiple paragraphs:

**This entire phrase is bold.**
*This whole sentence is italic.*

If you need a multi-paragraph emphasis effect, you will need to mark each paragraph individually. This is by design; multi-paragraph emphasis is a rare typographic need and usually signals that a different structural element (a blockquote or a callout component) is more appropriate.

What Are the Most Common Emphasis Mistakes in Markdown?

Spaces inside emphasis markers. * italic * (with spaces after the asterisk) will not render as italic in most parsers. The content must start immediately after the opening marker: *italic*.

Unpaired markers. A single asterisk with no closing pair is rendered as a literal asterisk. If your bold or italic is not rendering, check for an unclosed marker somewhere in the document.

Emphasis inside code spans. Markdown emphasis markers are not processed inside backtick code spans. `**not bold**` renders as literal asterisks inside a code span, which is the correct behavior.

Emphasis and punctuation. Place your closing emphasis marker before punctuation in most cases:

Read *Moby-Dick*, the classic novel.    (correct)
Read *Moby-Dick,* the classic novel.    (acceptable but less clean)

What Are the Best Practices for Using Emphasis in Markdown?

Limit bold to the most important phrase per section. If every paragraph has multiple bolded phrases, the visual hierarchy breaks down and readers stop responding to the signal.

Use italics for exactly the things italics are for. Titles, foreign terms, technical introductions. Using italics for casual emphasis weakens the convention over time.

Never use emphasis to substitute for document structure. If you find yourself bolding entire sentences repeatedly, that is a sign you need a heading or a callout block, not more emphasis.

Be consistent across a document. If you bold a term on first introduction, bold it consistently throughout (or switch to normal text after the introduction). Inconsistent emphasis looks careless and confuses readers about what is being emphasized.

Avoid stacking too many emphasis types. Bold-italic-highlight-strikethrough on the same word is visually noisy and semantically unclear. One type of emphasis per phrase is almost always enough.

How Do You See Emphasis Rendered in Real Time?

The fastest way to understand how emphasis renders is to try it yourself. Open edtr.md and experiment with the syntax in this guide. Type **bold**, *italic*, ~~strikethrough~~, and ***bold italic*** in the editor and watch the preview update in real time.

For a complete reference of everything in standard markdown beyond emphasis, including links, images, tables, and code blocks, the how to write in markdown guide has it all in one place. If you are just getting started and want a gentler introduction to the full markdown syntax, the markdown for beginners guide is the right starting point.