Markdown Emphasis Nesting & Precedence
Last updated: 2026-10-14
Emphasis Nesting & Precedence CommonMark core
How * and _ open and close emphasis is CommonMark's hairiest rule set — flanking (which side of the text the marker hugs). Most cross-renderer emphasis quirks trace back here.
| Group | Edge Cases & Rules |
|---|---|
| Spec level | CommonMark core |
| Spec version | CommonMark 0.31.2 + GFM |
📝 Syntax
mix *italic* and **bold** per level▶ Live Example
Edit Markdown on the left, see the result on the right
💡 Key points
⚠️ Warning Same-marker nesting (*a *b* c*) is ambiguous across renderers — avoid it.
💡 Tip Mix markers per level (* inside _), or use HTML <em>/<strong> for complex cases.
❓ FAQ
Q Why is the rule set so complex?
A Legacy: CommonMark models real-world Markdown.pl output with flanking rules.
Q What is the safest nesting style?
A Different marker per level (**_bold italic_**), or semantic HTML tags.
Q What is special about underscore flanking?
A Intraword underscores never emphasize (snake_case stays safe); asterisks have no such rule.
📚 See also
BoldCommonMark core ItalicCommonMark core