Syntax
<p><dfn>Hoisting</dfn> is JavaScript's behavior of moving declarations to the top of scope.</p>Examples
Defining a Technical Term
Introducing and defining a term the first time it appears.
<p>A <dfn>closure</dfn> is a function bundled together with references to its surrounding state.</p>Defining Term with a Title Attribute
Adding a short definition as a tooltip.
<p><dfn title="A reusable block of code that performs a task">Function</dfn> declarations start with the function keyword.</p>Best practices
- Use <dfn> only at the point where a term is actually being defined, not every time it is mentioned afterward
- Combine with a title attribute or nearby explanation so the definition is genuinely available, not just implied by italics
- Consider pairing with a glossary section using a definition list for a list of defined terms
- Do not use dfn purely for italic styling on unrelated text
Browser compatibility
Support applies to the named feature, not every attribute or behaviour in this article. Versions refer to browsers, not operating systems.
<dfn>
Desktop
- Chrome
- Supported
From 15 - Firefox
- Supported
From 1 - Safari
- Supported
From 6 - Edge
- Supported
From 12 - Opera
- Supported
From 15
Mobile
- Safari on iOS
- Supported
From 6 - Chrome for Android
- Supported
From 18 - Firefox for Android
- Supported
From 4 - Samsung Internet
- Supported
From 1.0
MDN BCD record for this feature · MDN reference
Support history and limitations
Chrome
- From 15
Firefox
- From 1
Safari
- From 6
Edge
- From 12
Opera
- From 15
Safari on iOS
- From 6
Chrome for Android
- From 18
Firefox for Android
- From 4
Samsung Internet
- From 1.0
MDN BCD 8.1.5 · Dataset built 2026-10-08 · Mapping reviewed 2026-10-21. These dates are not individual browser-test or claim-verification dates. Unknown means the data does not establish support.