English
ENIndo-EuropeanEnglish
Spoken by approximately 1.5 billion people worldwide
Writing Systems
Countries
Usage in Code
<!-- HTML lang attribute -->
<html lang="en">
/* CSS language selector */
:lang(en) { font-family: sans-serif; }
/* Accept-Language header */
Accept-Language: en
/* Intl API */
new Intl.DateTimeFormat('en').format(new Date())About English
English (English) is a Indo-European language identified by the ISO 639-1 code "en". It is spoken by approximately 1.5 billion people, primarily in United States, United Kingdom, Australia, Canada, India. The language uses the Latin writing system.
In web development, the ISO 639-1 language code is used in HTML lang attributes, HTTP Accept-Language headers, the JavaScript Intl API for locale-aware formatting, and content negotiation. Setting the correct language code improves accessibility for screen readers, enables proper text-to-speech pronunciation, and helps search engines serve content to the right audience. Browsers use this code for spell-checking, hyphenation, and font selection.
For SEO, specifying the content language via the lang attribute and hreflang tags helps search engines understand which language version of a page to show to users in different regions. This is essential for multilingual websites targeting international audiences.