3. Registry Format and Maintenance
This section defines the Language Subtag Registry and the maintenance
and update procedures associated with it, as well as a registry for
extensions to language tags (Section 3.7).
The Language Subtag Registry contains a comprehensive list of all of
the subtags valid in language tags. This allows implementers a
straightforward and reliable way to validate language tags. The
Language Subtag Registry will be maintained so that, except for
extension subtags, it is possible to validate all of the subtags that
appear in a language tag under the provisions of this document or its
revisions or successors. In addition, the meaning of the various
subtags will be unambiguous and stable over time. (The meaning of
private use subtags, of course, is not defined by the IANA registry.)
3.1. Format of the IANA Language Subtag Registry
The IANA Language Subtag Registry ("the registry") consists of a text
file that is machine readable in the format described in this
section, plus copies of the registration forms approved in accordance
with the process described in Section 3.5. The existing registration
forms for grandfathered and redundant tags taken from RFC 3066 will
be maintained as part of the obsolete RFC 3066 registry. The
remaining set of initial subtags will not have registration forms
created for them.
The registry is in the text format described below. This format was
based on the record-jar format described in [record-jar].
Each line of text is limited to 72 characters, including all
whitespace. Records are separated by lines containing only the
sequence "%%" (%x25.25).
Each field can be viewed as a single, logical line of ASCII
characters, comprising a field-name and a field-body separated by a
COLON character (%x3A). For convenience, the field-body portion of
this conceptual entity can be split into a multiple-line
representation; this is called "folding". The format of the registry
is described by the following ABNF (per [RFC4234]):
registry = record *("%%" CRLF record)
record = 1*( field-name *SP ":" *SP field-body CRLF )
field-name = (ALPHA / DIGIT) [*(ALPHA / DIGIT / "-") (ALPHA / DIGIT)]
field-body = *(ASCCHAR/LWSP)
ASCCHAR = %x21-25 / %x27-7E / UNICHAR ; Note: AMPERSAND is %x26
UNICHAR = "&#x" 2*6HEXDIG ";"
Figure 2: Registry Format ABNF
The sequence '..' (%x2E.2E) in a field-body denotes a range of
values. Such a range represents all subtags of the same length that
are in alphabetic or numeric order within that range, including the
values explicitly mentioned. For example 'a..c' denotes the values
'a', 'b', and 'c' and '11..13' denotes the values '11', '12', and
Characters from outside the US-ASCII [ISO646] repertoire, as well as
the AMPERSAND character ("&", %x26) when it occurs in a field-body,
are represented by a "Numeric Character Reference" using hexadecimal
notation in the style used by [XML10] (see
<http://www.w3.org/TR/REC-xml/#dt-charref>). This consists of the
sequence "&#x" (%x26.23.78) followed by a hexadecimal representation
of the character's code point in [ISO10646] followed by a closing
semicolon (%x3B). For example, the EURO SIGN, U+20AC, would be
represented by the sequence "€". Note that the hexadecimal
notation MAY have between two and six digits.
All fields whose field-body contains a date value use the "full-date"
format specified in [RFC3339]. For example: "2004-06-28" represents
June 28, 2004, in the Gregorian calendar.
The first record in the file contains the single field whose field-
name is "File-Date" (see Figure 3). The field-body of this record
contains the last modification date of this copy of the registry,
making it possible to compare different versions of the registry.
The registry on the IANA website is the most current. Versions with
an older date than that one are not up-to-date.
Figure 3: Example of the File-Date Record
Subsequent records represent subtags in the registry. Each of the
fields in each record MUST occur no more than once, unless otherwise
noted below. Each record MUST contain the following fields:
* Type's field-value MUST consist of one of the following
strings: "language", "extlang", "script", "region", "variant",
"grandfathered", and "redundant" and denotes the type of tag or
o Either 'Subtag' or 'Tag'
* Subtag's field-value contains the subtag being defined. This
field MUST only appear in records of whose 'Type' has one of
these values: "language", "extlang", "script", "region", or
* Tag's field-value contains a complete language tag. This field
MUST only appear in records whose 'Type' has one of these
values: "grandfathered" or "redundant". Note that the field-
value will always follow the 'grandfathered' production in the
ABNF in Section 2.1
* Description's field-value contains a non-normative description
of the subtag or tag.
* Added's field-value contains the date the record was added to
The 'Subtag' or 'Tag' field MUST use lowercase letters to form the
subtag or tag, with two exceptions. Subtags whose 'Type' field is
'script' (in other words, subtags defined by ISO 15924) MUST use
titlecase. Subtags whose 'Type' field is 'region' (in other words,
subtags defined by ISO 3166) MUST use uppercase. These exceptions
mirror the use of case in the underlying standards.
The field 'Description' MAY appear more than one time and contains a
description of the tag or subtag in the record. At least one of the
'Description' fields MUST be written or transcribed into the Latin
script; the same or additional fields MAY also include a description
in a non-Latin script. The 'Description' field is used for
identification purposes and SHOULD NOT be taken to represent the
actual native name of the language or variation or to be in any
particular language. Most descriptions are taken directly from
source standards such as ISO 639 or ISO 3166.
Note: Descriptions in registry entries that correspond to ISO 639,
ISO 15924, ISO 3166, or UN M.49 codes are intended only to indicate
the meaning of that identifier as defined in the source standard at
the time it was added to the registry. The description does not
replace the content of the source standard itself. The descriptions
are not intended to be the English localized names for the subtags.
Localization or translation of language tag and subtag descriptions
is out of scope of this document.
Each record MAY also contain the following fields:
* For fields of type 'language', 'extlang', 'script', 'region',
and 'variant', 'Preferred-Value' contains the subtag of the
same 'Type' that is preferred for forming the language tag.
* For fields of type 'grandfathered' and 'redundant', a canonical
mapping to a complete language tag.
* Deprecated's field-value contains the date the record was
* Prefix's field-value contains a language tag with which this
subtag MAY be used to form a new language tag, perhaps with
other subtags as well. This field MUST only appear in records
whose 'Type' field-value is 'variant' or 'extlang'. For
example, the 'Prefix' for the variant 'nedis' is 'sl', meaning
that the tags "sl-nedis" and "sl-IT-nedis" might be appropriate
while the tag "is-nedis" is not.
* Comments contains additional information about the subtag, as
deemed appropriate for understanding the registry and
implementing language tags using the subtag or tag.
* Suppress-Script contains a script subtag that SHOULD NOT be
used to form language tags with the associated primary language
subtag. This field MUST only appear in records whose 'Type'
field-value is 'language'. See Section 4.1.
The field 'Deprecated' MAY be added to any record via the maintenance
process described in Section 3.3 or via the registration process
described in Section 3.5. Usually, the addition of a 'Deprecated'
field is due to the action of one of the standards bodies, such as
ISO 3166, withdrawing a code. In some historical cases, it might not
have been possible to reconstruct the original deprecation date. For
these cases, an approximate date appears in the registry. Although
valid in language tags, subtags and tags with a 'Deprecated' field
are deprecated and validating processors SHOULD NOT generate these
subtags. Note that a record that contains a 'Deprecated' field and
no corresponding 'Preferred-Value' field has no replacement mapping.
The field 'Preferred-Value' contains a mapping between the record in
which it appears and another tag or subtag. The value in this field
is STRONGLY RECOMMENDED as the best choice to represent the value of
this record when selecting a language tag. These values form three
1. ISO 639 language codes that were later withdrawn in favor of
other codes. These values are mostly a historical curiosity.
2. ISO 3166 region codes that have been withdrawn in favor of a new
code. This sometimes happens when a country changes its name or
administration in such a way that warrants a new region code.
3. Tags grandfathered from RFC 3066. In many cases, these tags have
become obsolete because the values they represent were later
encoded by ISO 639.
Records that contain a 'Preferred-Value' field MUST also have a
'Deprecated' field. This field contains a date of deprecation.
Thus, a language tag processor can use the registry to construct the
valid, non-deprecated set of subtags for a given date. In addition,
for any given tag, a processor can construct the set of valid
language tags that correspond to that tag for all dates up to the
date of the registry. The ability to do these mappings MAY be
beneficial to applications that are matching, selecting, for
filtering content based on its language tags.
Note that 'Preferred-Value' mappings in records of type 'region'
sometimes do not represent exactly the same meaning as the original
value. There are many reasons for a country code to be changed, and
the effect this has on the formation of language tags will depend on
the nature of the change in question.
In particular, the 'Preferred-Value' field does not imply retagging
content that uses the affected subtag.
The field 'Preferred-Value' MUST NOT be modified once created in the
registry. The field MAY be added to records of type "grandfathered"
and "region" according to the rules in Section 3.3. Otherwise the
field MUST NOT be added to any record already in the registry.
The 'Preferred-Value' field in records of type "grandfathered" and
"redundant" contains whole language tags that are strongly
RECOMMENDED for use in place of the record's value. In many cases,
the mappings were created by deprecation of the tags during the
period before this document was adopted. For example, the tag
"no-nyn" was deprecated in favor of the ISO 639-1-defined language
Records of type 'variant' MAY have more than one field of type
'Prefix'. Additional fields of this type MAY be added to a 'variant'
record via the registration process.
Records of type 'extlang' MUST have _exactly_ one 'Prefix' field.
The field-value of the 'Prefix' field consists of a language tag
whose subtags are appropriate to use with this subtag. For example,
the variant subtag '1996' has a 'Prefix' field of "de". This means
that tags starting with the sequence "de-" are appropriate with this
subtag, so "de-Latg-1996" and "de-CH-1996" are both acceptable, while
the tag "fr-1996" is an inappropriate choice.
The field of type 'Prefix' MUST NOT be removed from any record. The
field-value for this type of field MUST NOT be modified.
The field 'Comments' MAY appear more than once per record. This
field MAY be inserted or changed via the registration process and no
guarantee of stability is provided. The content of this field is not
restricted, except by the need to register the information, the
suitability of the request, and by reasonable practical size
The field 'Suppress-Script' MUST only appear in records whose 'Type'
field-value is 'language'. This field MUST NOT appear more than one
time in a record. This field indicates a script used to write the
overwhelming majority of documents for the given language and that
therefore adds no distinguishing information to a language tag. It
helps ensure greater compatibility between the language tags
generated according to the rules in this document and language tags
and tag processors or consumers based on RFC 3066. For example,
virtually all Icelandic documents are written in the Latin script,
making the subtag 'Latn' redundant in the tag "is-Latn".
3.2. Language Subtag Reviewer
The Language Subtag Reviewer is appointed by the IESG for an
indefinite term, subject to removal or replacement at the IESG's
discretion. The Language Subtag Reviewer moderates the ietf-
languages mailing list, responds to requests for registration, and
performs the other registry maintenance duties described in
Section 3.3. Only the Language Subtag Reviewer is permitted to
request IANA to change, update, or add records to the Language Subtag
The performance or decisions of the Language Subtag Reviewer MAY be
appealed to the IESG under the same rules as other IETF decisions
(see [RFC2026]). The IESG can reverse or overturn the decision of
the Language Subtag Reviewer, provide guidance, or take other
3.3. Maintenance of the Registry
Maintenance of the registry requires that as codes are assigned or
withdrawn by ISO 639, ISO 15924, ISO 3166, and UN M.49, the Language
Subtag Reviewer MUST evaluate each change, determine whether it
conflicts with existing registry entries, and submit the information
to IANA for inclusion in the registry. If a change takes place and
the Language Subtag Reviewer does not do this in a timely manner,
then any interested party MAY use the procedure in Section 3.5 to
register the appropriate update.
Note: The redundant and grandfathered entries together are the
complete list of tags registered under [RFC3066]. The redundant tags
are those that can now be formed using the subtags defined in the
registry together with the rules of Section 2.2. The grandfathered
entries include those that can never be legal under those same
The set of redundant and grandfathered tags is permanent and stable:
new entries in this section MUST NOT be added and existing entries
MUST NOT be removed. Records of type 'grandfathered' MAY have their
type converted to 'redundant'; see item 12 in Section 3.6 for more
information. The decision-making process about which tags were
initially grandfathered and which were made redundant is described in
RFC 3066 tags that were deprecated prior to the adoption of this
document are part of the list of grandfathered tags, and their
component subtags were not included as registered variants (although
they remain eligible for registration). For example, the tag
"art-lojban" was deprecated in favor of the language subtag 'jbo'.
The Language Subtag Reviewer MUST ensure that new subtags meet the
requirements in Section 4.1 or submit an appropriate alternate subtag
as described in that section. When either a change or addition to
the registry is needed, the Language Subtag Reviewer MUST prepare the
complete record, including all fields, and forward it to IANA for
insertion into the registry. Each record being modified or inserted
MUST be forwarded in a separate message.
If a record represents a new subtag that does not currently exist in
the registry, then the message's subject line MUST include the word
"INSERT". If the record represents a change to an existing subtag,
then the subject line of the message MUST include the word "MODIFY".
The message MUST contain both the record for the subtag being
inserted or modified and the new File-Date record. Here is an
example of what the body of the message might contain:
LANGUAGE SUBTAG MODIFICATION
Description: Natisone dialect
Description: Nadiza dialect
Comments: This is a comment shown
as an example.
Figure 4: Example of a Language Subtag Modification Form
Whenever an entry is created or modified in the registry, the
'File-Date' record at the start of the registry is updated to reflect
the most recent modification date in the [RFC3339] "full-date"
Before forwarding a new registration to IANA, the Language Subtag
Reviewer MUST ensure that values in the 'Subtag' field match case
according to the description in Section 3.1.
3.4. Stability of IANA Registry Entries
The stability of entries and their meaning in the registry is
critical to the long-term stability of language tags. The rules in
this section guarantee that a specific language tag's meaning is
stable over time and will not change.
These rules specifically deal with how changes to codes (including
withdrawal and deprecation of codes) maintained by ISO 639, ISO
15924, ISO 3166, and UN M.49 are reflected in the IANA Language
Subtag Registry. Assignments to the IANA Language Subtag Registry
MUST follow the following stability rules:
1. Values in the fields 'Type', 'Subtag', 'Tag', 'Added',
'Deprecated' and 'Preferred-Value' MUST NOT be changed and are
guaranteed to be stable over time.
2. Values in the 'Description' field MUST NOT be changed in a way
that would invalidate previously-existing tags. They MAY be
broadened somewhat in scope, changed to add information, or
adapted to the most common modern usage. For example, countries
occasionally change their official names; a historical example
of this would be "Upper Volta" changing to "Burkina Faso".
3. Values in the field 'Prefix' MAY be added to records of type
'variant' via the registration process.
4. Values in the field 'Prefix' MAY be modified, so long as the
modifications broaden the set of prefixes. That is, a prefix
MAY be replaced by one of its own prefixes. For example, the
prefix "en-US" could be replaced by "en", but not by the
prefixes "en-Latn", "fr", or "en-US-boont". If one of those
prefixes were needed, a new Prefix SHOULD be registered.
5. Values in the field 'Prefix' MUST NOT be removed.
6. The field 'Comments' MAY be added, changed, modified, or removed
via the registration process or any of the processes or
considerations described in this section.
7. The field 'Suppress-Script' MAY be added or removed via the
8. Codes assigned by ISO 639, ISO 15924, and ISO 3166 that do not
conflict with existing subtags of the associated type and whose
meaning is not the same as an existing subtag of the same type
are entered into the IANA registry as new records.
9. Codes assigned by ISO 639, ISO 15924, or ISO 3166 that are
withdrawn by their respective maintenance or registration
authority remain valid in language tags. A 'Deprecated' field
containing the date of withdrawal is added to the record. If a
new record of the same type is added that represents a
replacement value, then a 'Preferred-Value' field MAY also be
added. The registration process MAY be used to add comments
about the withdrawal of the code by the respective standard.
The region code 'TL' was assigned to the country 'Timor-
Leste', replacing the code 'TP' (which was assigned to 'East
Timor' when it was under administration by Portugal). The
subtag 'TP' remains valid in language tags, but its record
contains the a 'Preferred-Value' of 'TL' and its field
'Deprecated' contains the date the new code was assigned
10. Codes assigned by ISO 639, ISO 15924, or ISO 3166 that conflict
with existing subtags of the associated type, including subtags
that are deprecated, MUST NOT be entered into the registry. The
following additional considerations apply to subtag values that
A. For ISO 639 codes, if the newly assigned code's meaning is
not represented by a subtag in the IANA registry, the
Language Subtag Reviewer, as described in Section 3.5, SHALL
prepare a proposal for entering in the IANA registry as soon
as practical a registered language subtag as an alternate
value for the new code. The form of the registered language
subtag will be at the discretion of the Language Subtag
Reviewer and MUST conform to other restrictions on language
subtags in this document.
B. For all subtags whose meaning is derived from an external
standard (i.e., ISO 639, ISO 15924, ISO 3166, or UN M.49),
if a new meaning is assigned to an existing code and the new
meaning broadens the meaning of that code, then the meaning
for the associated subtag MAY be changed to match. The
meaning of a subtag MUST NOT be narrowed, however, as this
can result in an unknown proportion of the existing uses of
a subtag becoming invalid. Note: ISO 639 maintenance
agency/registration authority (MA/RA) has adopted a similar
C. For ISO 15924 codes, if the newly assigned code's meaning is
not represented by a subtag in the IANA registry, the
Language Subtag Reviewer, as described in Section 3.5, SHALL
prepare a proposal for entering in the IANA registry as soon
as practical a registered variant subtag as an alternate
value for the new code. The form of the registered variant
subtag will be at the discretion of the Language Subtag
Reviewer and MUST conform to other restrictions on variant
subtags in this document.
D. For ISO 3166 codes, if the newly assigned code's meaning is
associated with the same UN M.49 code as another 'region'
subtag, then the existing region subtag remains as the
preferred value for that region and no new entry is created.
A comment MAY be added to the existing region subtag
indicating the relationship to the new ISO 3166 code.
E. For ISO 3166 codes, if the newly assigned code's meaning is
associated with a UN M.49 code that is not represented by an
existing region subtag, then the Language Subtag Reviewer,
as described in Section 3.5, SHALL prepare a proposal for
entering the appropriate UN M.49 country code as an entry in
the IANA registry.
F. For ISO 3166 codes, if there is no associated UN numeric
code, then the Language Subtag Reviewer SHALL petition the
UN to create one. If there is no response from the UN
within ninety days of the request being sent, the Language
Subtag Reviewer SHALL prepare a proposal for entering in the
IANA registry as soon as practical a registered variant
subtag as an alternate value for the new code. The form of
the registered variant subtag will be at the discretion of
the Language Subtag Reviewer and MUST conform to other
restrictions on variant subtags in this document. This
situation is very unlikely to ever occur.
11. UN M.49 has codes for both countries and areas (such as '276'
for Germany) and geographical regions and sub-regions (such as
'150' for Europe). UN M.49 country or area codes for which
there is no corresponding ISO 3166 code SHOULD NOT be
registered, except as a surrogate for an ISO 3166 code that is
blocked from registration by an existing subtag. If such a code
becomes necessary, then the registration authority for ISO 3166
SHOULD first be petitioned to assign a code to the region. If
the petition for a code assignment by ISO 3166 is refused or not
acted on in a timely manner, the registration process described
in Section 3.5 MAY then be used to register the corresponding UN
M.49 code. At the time this document was written, there were
only four such codes: 830 (Channel Islands), 831 (Guernsey), 832
(Jersey), and 833 (Isle of Man). This way, UN M.49 codes remain
available as the value of last resort in cases where ISO 3166
reassigns a deprecated value in the registry.
12. Stability provisions apply to grandfathered tags with this
exception: should all of the subtags in a grandfathered tag
become valid subtags in the IANA registry, then the field 'Type'
in that record is changed from 'grandfathered' to 'redundant'.
Note that this will not affect language tags that match the
grandfathered tag, since these tags will now match valid
generative subtag sequences. For example, if the subtag 'gan'
in the language tag "zh-gan" were to be registered as an
extended language subtag, then the grandfathered tag "zh-gan"
would be deprecated (but existing content or implementations
that use "zh-gan" would remain valid).
3.5. Registration Procedure for Subtags
The procedure given here MUST be used by anyone who wants to use a
subtag not currently in the IANA Language Subtag Registry.
Only subtags of type 'language' and 'variant' will be considered for
independent registration of new subtags. Handling of subtags needed
for stability and subtags necessary to keep the registry synchronized
with ISO 639, ISO 15924, ISO 3166, and UN M.49 within the limits
defined by this document are described in Section 3.3. Stability
provisions are described in Section 3.4.
This procedure MAY also be used to register or alter the information
for the 'Description', 'Comments', 'Deprecated', or 'Prefix' fields
in a subtag's record as described in Section 3.4. Changes to all
other fields in the IANA registry are NOT permitted.
Registering a new subtag or requesting modifications to an existing
tag or subtag starts with the requester filling out the registration
form reproduced below. Note that each response is not limited in
size so that the request can adequately describe the registration.
The fields in the "Record Requested" section SHOULD follow the
requirements in Section 3.1.
LANGUAGE SUBTAG REGISTRATION FORM
1. Name of requester:
2. E-mail address of requester:
3. Record Requested:
4. Intended meaning of the subtag:
5. Reference to published description
of the language (book or article):
6. Any other relevant information:
Figure 5: The Language Subtag Registration Form
The subtag registration form MUST be sent to
<email@example.com> for a two-week review period before it can
be submitted to IANA. (This is an open list and can be joined by
sending a request to <firstname.lastname@example.org>.)
Variant subtags are usually registered for use with a particular
range of language tags. For example, the subtag 'rozaj' is intended
for use with language tags that start with the primary language
subtag "sl", since Resian is a dialect of Slovenian. Thus, the
subtag 'rozaj' would be appropriate in tags such as "sl-Latn-rozaj"
or "sl-IT-rozaj". This information is stored in the 'Prefix' field
in the registry. Variant registration requests SHOULD include at
least one 'Prefix' field in the registration form.
Extended language subtags are reserved for future standardization.
These subtags will be REQUIRED to include exactly one 'Prefix' field
once they are allowed for registration.
The 'Prefix' field for a given registered subtag exists in the IANA
registry as a guide to usage. Additional prefixes MAY be added by
filing an additional registration form. In that form, the "Any other
relevant information:" field MUST indicate that it is the addition of
Requests to add a prefix to a variant subtag that imply a different
semantic meaning will probably be rejected. For example, a request
to add the prefix "de" to the subtag 'nedis' so that the tag
"de-nedis" represented some German dialect would be rejected. The
'nedis' subtag represents a particular Slovenian dialect and the
additional registration would change the semantic meaning assigned to
the subtag. A separate subtag SHOULD be proposed instead.
The 'Description' field MUST contain a description of the tag being
registered written or transcribed into the Latin script; it MAY also
include a description in a non-Latin script. Non-ASCII characters
MUST be escaped using the syntax described in Section 3.1. The
'Description' field is used for identification purposes and doesn't
necessarily represent the actual native name of the language or
variation or to be in any particular language.
While the 'Description' field itself is not guaranteed to be stable
and errata corrections MAY be undertaken from time to time, attempts
to provide translations or transcriptions of entries in the registry
itself will probably be frowned upon by the community or rejected
outright, as changes of this nature have an impact on the provisions
in Section 3.4.
When the two-week period has passed, the Language Subtag Reviewer
either forwards the record to be inserted or modified to
email@example.com according to the procedure described in Section 3.3, or
rejects the request because of significant objections raised on the
list or due to problems with constraints in this document (which MUST
be explicitly cited). The Language Subtag Reviewer MAY also extend
the review period in two-week increments to permit further
discussion. The Language Subtag Reviewer MUST indicate on the list
whether the registration has been accepted, rejected, or extended
following each two-week period.
Note that the Language Subtag Reviewer MAY raise objections on the
list if he or she so desires. The important thing is that the
objection MUST be made publicly.
The applicant is free to modify a rejected application with
additional information and submit it again; this restarts the two-
week comment period.
Decisions made by the Language Subtag Reviewer MAY be appealed to the
IESG [RFC2028] under the same rules as other IETF decisions
All approved registration forms are available online in the directory
http://www.iana.org/numbers.html under "languages".
Updates or changes to existing records follow the same procedure as
new registrations. The Language Subtag Reviewer decides whether
there is consensus to update the registration following the two-week
review period; normally, objections by the original registrant will
carry extra weight in forming such a consensus.
Registrations are permanent and stable. Once registered, subtags
will not be removed from the registry and will remain a valid way in
which to specify a specific language or variant.
Note: The purpose of the "Description" in the registration form is to
aid people trying to verify whether a language is registered or what
language or language variation a particular subtag refers to. In
most cases, reference to an authoritative grammar or dictionary of
that language will be useful; in cases where no such work exists,
other well-known works describing that language or in that language
MAY be appropriate. The Language Subtag Reviewer decides what
constitutes "good enough" reference material. This requirement is
not intended to exclude particular languages or dialects due to the
size of the speaker population or lack of a standardized orthography.
Minority languages will be considered equally on their own merits.
3.6. Possibilities for Registration
Possibilities for registration of subtags or information about
o Primary language subtags for languages not listed in ISO 639 that
are not variants of any listed or registered language MAY be
registered. At the time this document was created, there were no
examples of this form of subtag. Before attempting to register a
language subtag, there MUST be an attempt to register the language
with ISO 639. Subtags MUST NOT be registered for codes that exist
in ISO 639-1 or ISO 639-2, that are under consideration by the ISO
639 maintenance or registration authorities, or that have never
been attempted for registration with those authorities. If ISO
639 has previously rejected a language for registration, it is
reasonable to assume that there must be additional, very
compelling evidence of need before it will be registered in the
IANA registry (to the extent that it is very unlikely that any
subtags will be registered of this type).
o Dialect or other divisions or variations within a language, its
orthography, writing system, regional or historical usage,
transliteration or other transformation, or distinguishing
variation MAY be registered as variant subtags. An example is the
'rozaj' subtag (the Resian dialect of Slovenian).
o The addition or maintenance of fields (generally of an
informational nature) in Tag or Subtag records as described in
Section 3.1 and subject to the stability provisions in
Section 3.4. This includes descriptions, comments, deprecation
and preferred values for obsolete or withdrawn codes, or the
addition of script or extlang information to primary language
o The addition of records and related field value changes necessary
to reflect assignments made by ISO 639, ISO 15924, ISO 3166, and
UN M.49 as described in Section 3.4.
Subtags proposed for registration that would cause all or part of a
grandfathered tag to become redundant but whose meaning conflicts
with or alters the meaning of the grandfathered tag MUST be rejected.
This document leaves the decision on what subtags or changes to
subtags are appropriate (or not) to the registration process
described in Section 3.5.
Note: four-character primary language subtags are reserved to allow
for the possibility of alpha4 codes in some future addition to the
ISO 639 family of standards.
ISO 639 defines a maintenance agency for additions to and changes in
the list of languages in ISO 639. This agency is:
International Information Centre for Terminology (Infoterm)
Aichholzgasse 6/12, AT-1120
Phone: +43 1 26 75 35 Ext. 312 Fax: +43 1 216 32 72
ISO 639-2 defines a maintenance agency for additions to and changes
in the list of languages in ISO 639-2. This agency is:
Library of Congress
Network Development and MARC Standards Office
Washington, D.C. 20540 USA
Phone: +1 202 707 6237 Fax: +1 202 707 0115
The maintenance agency for ISO 3166 (country codes) is:
ISO 3166 Maintenance Agency
c/o International Organization for Standardization
Case postale 56
CH-1211 Geneva 20 Switzerland
Phone: +41 22 749 72 33 Fax: +41 22 749 73 49
The registration authority for ISO 15924 (script codes) is:
Unicode Consortium Box 391476
Mountain View, CA 94039-1476, USA
The Statistics Division of the United Nations Secretariat maintains
the Standard Country or Area Codes for Statistical Use and can be
Statistical Services Branch
United Nations, Room DC2-1620
New York, NY 10017, USA
3.7. Extensions and Extensions Registry
Extension subtags are those introduced by single-character subtags
("singletons") other than 'x'. They are reserved for the generation
of identifiers that contain a language component and are compatible
with applications that understand language tags.
The structure and form of extensions are defined by this document so
that implementations can be created that are forward compatible with
applications that might be created using singletons in the future.
In addition, defining a mechanism for maintaining singletons will
lend stability to this document by reducing the likely need for
future revisions or updates.
Single-character subtags are assigned by IANA using the "IETF
Consensus" policy defined by [RFC2434]. This policy requires the
development of an RFC, which SHALL define the name, purpose,
processes, and procedures for maintaining the subtags. The
maintaining or registering authority, including name, contact email,
discussion list email, and URL location of the registry, MUST be
indicated clearly in the RFC. The RFC MUST specify or include each
of the following:
o The specification MUST reference the specific version or revision
of this document that governs its creation and MUST reference this
section of this document.
o The specification and all subtags defined by the specification
MUST follow the ABNF and other rules for the formation of tags and
subtags as defined in this document. In particular, it MUST
specify that case is not significant and that subtags MUST NOT
exceed eight characters in length.
o The specification MUST specify a canonical representation.
o The specification of valid subtags MUST be available over the
Internet and at no cost.
o The specification MUST be in the public domain or available via a
royalty-free license acceptable to the IETF and specified in the
o The specification MUST be versioned, and each version of the
specification MUST be numbered, dated, and stable.
o The specification MUST be stable. That is, extension subtags,
once defined by a specification, MUST NOT be retracted or change
in meaning in any substantial way.
o The specification MUST include in a separate section the
registration form reproduced in this section (below) to be used in
registering the extension upon publication as an RFC.
o IANA MUST be informed of changes to the contact information and
URL for the specification.
IANA will maintain a registry of allocated single-character
(singleton) subtags. This registry MUST use the record-jar format
described by the ABNF in Section 3.1. Upon publication of an
extension as an RFC, the maintaining authority defined in the RFC
MUST forward this registration form to firstname.lastname@example.org, who MUST
forward the request to email@example.com. The maintaining authority of
the extension MUST maintain the accuracy of the record by sending an
updated full copy of the record to firstname.lastname@example.org with the subject
line "LANGUAGE TAG EXTENSION UPDATE" whenever content changes. Only
the 'Comments', 'Contact_Email', 'Mailing_List', and 'URL' fields MAY
be modified in these updates.
Failure to maintain this record, maintain the corresponding registry,
or meet other conditions imposed by this section of this document MAY
be appealed to the IESG [RFC2028] under the same rules as other IETF
decisions (see [RFC2026]) and MAY result in the authority to maintain
the extension being withdrawn or reassigned by the IESG.
Figure 6: Format of Records in the Language Tag Extensions Registry
'Identifier' contains the single-character subtag (singleton)
assigned to the extension. The Internet-Draft submitted to define
the extension SHOULD specify which letter or digit to use, although
the IESG MAY change the assignment when approving the RFC.
'Description' contains the name and description of the extension.
'Comments' is an OPTIONAL field and MAY contain a broader description
of the extension.
'Added' contains the date the RFC was published in the "full-date"
format specified in [RFC3339]. For example: 2004-06-28 represents
June 28, 2004, in the Gregorian calendar.
'RFC' contains the RFC number assigned to the extension.
'Authority' contains the name of the maintaining authority for the
'Contact_Email' contains the email address used to contact the
'Mailing_List' contains the URL or subscription email address of the
mailing list used by the maintaining authority.
'URL' contains the URL of the registry for this extension.
The determination of whether an Internet-Draft meets the above
conditions and the decision to grant or withhold such authority rests
solely with the IESG and is subject to the normal review and appeals
process associated with the RFC process.
Extension authors are strongly cautioned that many (including most
well-formed) processors will be unaware of any special relationships
or meaning inherent in the order of extension subtags. Extension
authors SHOULD avoid subtag relationships or canonicalization
mechanisms that interfere with matching or with length restrictions
that sometimes exist in common protocols where the extension is used.
In particular, applications MAY truncate the subtags in doing
matching or in fitting into limited lengths, so it is RECOMMENDED
that the most significant information be in the most significant
(left-most) subtags and that the specification gracefully handle
When a language tag is to be used in a specific, known, protocol, it
is RECOMMENDED that the language tag not contain extensions not
supported by that protocol. In addition, note that some protocols
MAY impose upper limits on the length of the strings used to store or
transport the language tag.
3.8. Initialization of the Registries
Upon adoption of this document, an initial version of the Language
Subtag Registry containing the various subtags initially valid in a
language tag is necessary. This collection of subtags, along with a
description of the process used to create it, is described by
[RFC4645]. IANA SHALL publish the initial version of the registry
described by this document from the content of [RFC4645]. Once
published by IANA, the maintenance procedures, rules, and
registration processes described in this document will be available
for new registrations or updates.
Registrations that are in process under the rules defined in
[RFC3066] when this document is adopted MAY be completed under the
former rules, at the discretion of the Language Tag Reviewer (as
described in [RFC3066]). Until the IESG officially appoints a
Language Subtag Reviewer, the existing Language Tag Reviewer SHALL
serve as the Language Subtag Reviewer.
Any new registrations submitted using the RFC 3066 forms or format
after the adoption of this document and publication of the registry
by IANA MUST be rejected.
An initial version of the Language Tag Extensions Registry described
in Section 3.7 is also needed. The Language Tag Extensions Registry
SHALL be initialized with a single record containing a single field
of type "File-Date" as a placeholder for future assignments.