LC
ISOISO 639 is the international standard for language identification, providing the short alphabetic codes that libraries, information systems, and software applications use to represent languages. From MARC records to HTML lang attributes, ISO 639 codes are ubiquitous in metadata and computing. The standard is maintained through a multi-part structure, with the Library of Congress serving as the registration authority for the widely used three-letter codes in Part 2.
Background
The need for standardized language codes emerged in the 1960s as international information exchange grew. The original ISO 639 standard was first published in 1967, providing two-letter codes for a limited set of major languages. As demand for broader language coverage grew, Part 2 was developed in 1998 with three-letter codes covering nearly 500 languages. Part 3, maintained by SIL International, extended this to comprehensive coverage of all known human languages (over 7,000 codes). Additional parts address language groups and families (Part 5) and established a framework for the overall code space.
Purpose & Scope
ISO 639 assigns codes to individual languages and language groups for use in terminology, bibliography, and information systems. The standard is organized into several parts:
| Part | Code Length | Scope | Registration Authority |
|---|---|---|---|
| ISO 639-1 | 2 letters | Major world languages (~180 codes) | Infoterm |
| ISO 639-2 | 3 letters | Broader coverage (~490 codes), includes bibliographic (B) and terminological (T) variants | Library of Congress |
| ISO 639-3 | 3 letters | Comprehensive coverage of all known languages (~7,900 codes) | SIL International |
| ISO 639-5 | 3 letters | Language families and groups | Library of Congress |
Part 1 codes (e.g., en for English, fr for French) are the most widely used in web technologies and software localization. Part 2 codes (e.g., eng, fre/fra) are standard in library cataloging and MARC records.
Key Elements / Properties
Each entry in the ISO 639 code lists includes:
| Field | Description |
|---|---|
| Alpha-2 code | Two-letter code (Part 1 only) |
| Alpha-3 code | Three-letter code (Parts 2, 3, 5) |
| English name | The English name of the language |
| French name | The French name of the language |
| Bibliographic code | In Part 2, some languages have a separate bibliographic code derived from the English name |
| Terminological code | In Part 2, some languages have a separate terminological code derived from the native name |
Serializations & Technical Formats
The ISO 639 code lists are published as tabular datasets. The Library of Congress provides the ISO 639-2 code list in downloadable text format and as a searchable web database. ISO 639-3 code tables are available from SIL International in tab-delimited format. The codes themselves are embedded in MARC records (field 008, field 041), XML xml:lang attributes, HTML lang attributes, and HTTP Accept-Language headers, among many other contexts.
Governance & Maintenance
ISO 639 is maintained under ISO Technical Committee 37 (Terminology and other language and content resources). Individual parts have separate registration authorities: Infoterm for Part 1, the Library of Congress for Parts 2 and 5, and SIL International for Part 3. Requests for new codes or changes are submitted to the relevant registration authority, which evaluates them according to established criteria. The Library of Congress publishes an online form for requesting additions or changes to the ISO 639-2 code list.
Notable Implementations
ISO 639 codes are used in virtually every information system that deals with multilingual content. In libraries, they appear in MARC records and are fundamental to language-based searching and filtering. The IETF BCP 47 language tag standard builds on ISO 639 codes as its foundation. Web standards including HTML, XML, and HTTP use ISO 639 codes for language identification. Operating systems, programming language libraries, and localization frameworks all rely on these codes. The Unicode CLDR (Common Locale Data Repository) uses ISO 639 as the basis for its locale identifiers.
Related Standards
- MARC 21 -- Uses ISO 639-2 codes for language identification in bibliographic and authority records.
- IETF BCP 47 -- The standard for language tags on the Internet, which uses ISO 639 codes as its primary language subtags.