The HTML5 <bdi> tag is a new addition to the tags that can be used with HTML5. BDI stands for Bi Directional Isolation. The HTML5 <bdi> tag is an important one because it isolates a part of the text that might be formatted or oriented in a different direction from the other text surrounding it. It is also one of the new formatting tags under HTML5. The HTML5 <bdi> tag is useful when embedding user-generated content with an unknown directionality.
The HTML5 <bdi> tag is commonly used when including language written with right-to-left scripts in a document. Some examples of these languages are Arabic, Persian, Hebrew, Urdu, and others. This is what leads to mixing in words or phrases in English or some other language that uses a left-to-right script. The result is called bidirectional or bidi text.
Since the HTML5 <bdi> tag is fairly new, it is not yet supported by the major browsers such as Firefox, Safari, Internet Explorer, Opera, and Google Chrome. The HTML5 <bdi> tag has no functional counterpart in the HTML4.01 since this is new to the HTML5 environment.
The HTML5 <bdi> tag is also capable of supporting the Global Attributes and Event Attributes in HTML5.
Here is an example of the HTML5 <bdi> tag:
User <bdi>إيان</bdi>: 120 clicks