Flag icons for languages
The use of flag icons, particularly national flags, for languages is a common practice. Such icons have long been used on tourist attraction signage, and elsewhere in the tourism space, but have found wider use in website localization where UX limitations have become apparent.
The usage remains widespread despite problems, such as being potentially insulting, since countries and languages don't have a one-to-one correspondence. The World [Wide Web Consortium] suggests not using such practice, and recommends using texts instead.
Types of flags icons
are the most commonly used flag icons for representing languages. They are generally chosen because they either represent the language's origin or the highest number of native speakers.
A diagonally divided flag between two or more nation states is sometimes used when more than one country is a major user of a language. Examples of this are the flags of the United Kingdom and the United States to indicate the English language; the flags of China and Taiwan to represent Mandarin; the flags of France, Belgium, and Canada to represent the French language; the flags of Spain and Mexico to represent the Spanish language; the flags of Portugal and Brazil to represent the Portuguese language; and the flags of Germany, Austria, and Switzerland to represent the German language.
Linguistic flags
Some international linguistic communities, particularly those of international auxiliary languages, have flags which encompass all the speakers of a language while avoiding the symbolism of national flags, though they are not as widely recognized.
Writing systems
National flags can also be used to distinguish between different written standards for a single language. For example, the flag of Taiwan is often used for Traditional Chinese and the flag of the [People's Republic of China] for Simplified Chinese.
Political motivations
Some Euronet ATMs display the Irish flag as a symbol for the English language. This was speculated to be a response to Brexit, with the Republic of Ireland as one of the only two remaining European Union member nations with English among their official languages. The Irish flag is more commonly used to signify the Irish language.