The name of the bdo element stands for bidirectional override. The lang and dir attributes of most elements are designed to take care of most situations involving the mixture of writing systems that compose text in opposite directions. The bdo element is designed to assist in instances when the normal bidirectional algorithms must be explicitly overridden, due to various conversions during text processing. Because this element is not yet implemented in browsers, it is detailed here for informational purposes only.

The language being used for the element's attribute values and content. A browser can use this information to assist in proper rendering of content with respect to details such as treatment of ligatures (when supported by a particular font or required by a written language), quotation marks, and hyphenation. Other applications and search engines might use this information to aid the selection of spell-checking dictionaries and the creation of indices.