Conditional comment

In <a href="/facts/Internet_Explorer/uL8a4Y5l">Internet Explorer</a> (IE) versions <a href="/facts/Internet_Explorer_5/HaSYzQEg">5</a> through <a href="/facts/Internet_Explorer_9/A78zjnWY">9</a>, a conditional comment is text formatted as a <a href="/facts/Comment_(computer_programming)/Q8hHFq8h">comment</a> in <a href="/facts/HTML/sSc3fT78">HTML</a> <a href="/facts/Source_code/o9J6Jv23">source code</a> with special syntax that IE interprets as a <a href="/facts/Conditional_(computer_programming)/8gDQTqUD">conditional statement</a>. A conditional comment specifies whether to include or exclude code based on the evaluation of a <a href="/facts/Conditional_expression/8gDQTqUD">conditional expression</a> and is generally used to support different versions of IE or a browser other than IE.
Support for conditional comments was introduced in IE version 5 and dropped in version 10. In IE 10, conditional comments are not supported when the page is in standards mode (document mode 10). There exists an adjacent technology in <a href="/facts/JScript/HyuCUU2D">JScript</a> (Microsoft's non-standard implementation of <a href="/facts/JavaScript/XhhIIEsl">JavaScript</a>) called conditional compilation, which uses @-prefixed codes in the style of preprocessor macros in C and C++. Conditional compilation was introduced in <a href="/facts/Internet_Explorer_4/ztoV77jR">IE 4</a>, and was supported up through IE 10, in both standards and compatibility modes.

Conditional comment open-in-new

Conditional comment