Unicode Technical Reports cover a wide range of
topics related to the implementation or development of the
Unicode Standard. These include topics such as:
- normalizing Unicode text for comparison and storage
- collating (sorting) Unicode strings
- determining line break opportunities or other segmentation boundaries in text
- regular expression syntax extensions for Unicode text
- compressing Unicode text
These reports are normatively referenced by a
number of international standards and by a wide range of
For a categorized list of the Unicode specifications, including specifications
defined in the Unicode Technical Reports and those defined in other locations in the
Unicode Standard, see the
Types of Unicode Technical Reports: UAX, UTS, UTR
There are three types of technical reports,
based on the authoritative status of the document:
A Unicode Standard Annex (UAX) forms an integral part
of the Unicode Standard, but is published as a separate
document. The Unicode Standard may require conformance to
normative content in a Unicode Standard Annex, if so specified
in the Conformance chapter of that version of the Unicode
Standard. The version number of a UAX document is always the same as
the version of the Unicode Standard of which it forms a part.
A Unicode Technical Standard (UTS) is an independent
specification. Conformance to the Unicode Standard does not
imply conformance to any UTS.
A Unicode Technical Report (UTR) contains informative
material. Conformance to the Unicode Standard does not imply
conformance to any UTR. Other specifications, however, are free
to make normative references to a UTR.
As technical reports, including UAXes and UTSes, are developed, the Unicode Technical
Committee approves the posting of proposed updates or preliminary versions for
public review. Publication of these draft versions does not
imply endorsement by the Unicode Consortium.
A Proposed Update of a UAX, UTS, or UTR
contains the draft of a proposed modification of an already published
UAX, UTS, or UTR.
A Draft Unicode Technical Report (DUTR)
has the basic structure and content required for a new technical report, but has not
yet received final approval for publication.
A Proposed Draft Unicode Technical Report (PDUTR)
is in an early stage of development.
Any technical report that has
Proposed Update, Draft, or Proposed Draft,
status is a preliminary document which may be updated,
replaced, or superseded by other documents at any time. Such
documents are not stable specifications; it is inappropriate to cite them
as other than works in progress. Their status is always clearly
indicated in the document.
Technical reports are created by the Unicode Consortium Technical
Committees (UTC and
CLDR-TC) following open,
For more information about the approval process,
see the FAQ on the Technical
Reports Development Process. When
appropriate, the Public
Review Issues page solicits review and feedback on initial drafts for or updates
to technical reports.
UTS #10, Unicode Collation Algorithm, has
an additional set of policies governing the maintenance
of the basic data table used in assigning collation weights
to characters. See
Change Management for the Unicode
Collation Algorithm and
UCA Default Table
Criteria for New Characters.
Each technical report has a unique and persistent report number that is part of its title.
For example, in UTS #10, Unicode Collation Algorithm, the "10" permanently
identifies that specification, and never changes as the document
The report numbers for stabilized, superseded or withdrawn reports
are never reused.
Each technical report also has a
revision number, which is then used to track and identify
each proposed update and each approved publication of the document.
UAXes and UTSes have a separate version number, in addition to their revision number.
The details of the meaning and assignment of version numbers for
those types of technical reports are specified below.
For information about citing versions of technical
reports, see Versions
of the Unicode Standard.
Uniform and persistent revision numbers are used
for all technical reports.
This revision number is incremented and a new URL reflecting that
revision number is provided
each time the file content is altered materially. Modifications to the
report are summarized in the change history section of each document.
Revision numbers are reflected directly in the permanent, versioned
file names used in the URL for the document. Thus,
Revision 30 of UTS #10 is named .../reports/tr10/tr10-30.html, while
the earlier Revision 28 of the same technical report is named
.../reports/tr10/tr10-28.html, and so on. There were some departures
from this scheme for very early publications, but this naming convention
is now followed for all technical reports.
Because revision numbers use whole
numbers, rather than a major.minor.update version syntax,
some technical reports have large revision numbers. Many
of the revision number changes, however, reflect
minor editorial changes to the documents, as
opposed to substantive changes to their contents.
editorial corrections such as fixing a broken link may be made without
assigning a new revision number. In such
cases the date in the report header will, however, be updated, to
indicate that a micro-edit has occurred.
Revision Back Link Trail
Each technical report has links to the
previous approved revision of the report and to the latest
approved revision of the report, allowing readers to find and
cite a particular revision. The back links to previous approved
revisions can be followed all the way back to the initial
drafts of the documents, if so desired, allowing examination
of the complete history of the specification.
Proposed update revisions of documents are not included
in the back link trail of previous approved revisions, but
any specific proposed update can still be accessed on
the Unicode website by using the relevant revision number
of that proposed update in the URL for the document.
Version Numbers for UAXes
Because each UAX is formally a part of version of the Unicode
Standard, it is given a version number in addition to its
revision number. The version number always matches the
version of the Unicode Standard that it constitutes a part
of, and the version number reflects the
same major.minor.update format of the Unicode Standard.
For details regarding how major.minor.update versioning is
used for the Unicode Standard, see
About Versions of the Unicode Standard.
Version Numbers for UTSes
UTSes also have a version number in addition to their
revision number, but the conventions for assignment of
version numbers for UTSes differ somewhat from UAXes.
In some cases UTSes use major.minor format version numbers to distinguish
minor updates of the documents from major changes in the
specification. Such version numbers apply only to the UTS
in question and are not synchronized with versions of
the Unicode Standard.
In other cases a UTS may have associated data which is maintained
in synchrony with repertoire additions to the Unicode Standard.
In those cases, the UTS may be given a major.minor.update
version number which matches the version of the Unicode Standard
reflected in the data files.
Over time, a particular UTS may change its maintenance status,
and change from development that is not synchronized with releases
of the Unicode Standard to development which is synchronized
with those releases. When this happens, the version numbering
scheme for the specification changes as well. For example,
UTS #39, Unicode Security Mechanisms, was first published
as Version 2, then Version 3, but changed to Version 6.3.0
when its maintenance mode changed to synchronize with the
Unicode Standard, Version 6.3.0.
Data files associated with UAXes are formally a part of the
Unicode Character Database (UCD),
an integral part of each version of
the Unicode Standard. Such data files are updated for each release
of the Unicode Standard. Often there are no substantive
changes required for particular data files, but the versions are bumped
and new files are published, so that implementers have
a complete set of data for each release.
Some UTSes are also associated with data files. If the UTS is
maintained in synchrony with the Unicode Standard, then its data
files are also updated with each release, and the naming conventions
for the UTS data directories also reflect the version numbering.
However, such data files are not formally a part of the Unicode
UTRs may also have associated data files. In such cases, because
a UTR has no version number distinct from its revision number,
the associated data files are published in a data directory which
reflects the revision number. A new revision data directory is
created each time the UTR itself is updated, but such revisions are
not synchronized with releases of the Unicode Standard.
Data files for UTSes or UTRs are
maintained in separate folders under
https://www.unicode.org/Public/. The location of each set of
data files is documented in the corresponding UTS or UTR. Each folder
contains a complete set of data files for that version of the
The UAXes, UTSes, and some of the UTRs have stable HTML anchors defined for section headers. These enable direct links to those sections. More recent versions of technical reports have stable HTML anchors for tables, figures, each formal rule or definition, and the modification history of the document. For example:
A superseded report has been replaced by or incorporated into some other specification.
Implementations and external specifications that claim conformance
should preferably be updated to the replacement.
For example, UAX #13 Newline Guidelines
became Section 5.8, Newline Guidelines
in the Core Specification of the Unicode Standard as of Version 4.0.
A withdrawn report is no longer supported by the Unicode Consortium.
A stabilized report is neither superseded nor withdrawn,
but no longer actively maintained — usually because
the specification is stable and no further development is anticipated.
Superseded, withdrawn and stabilized reports
are listed as such on the
Technical Reports page,
each with a link to a page explaining the change in status (Example).
Where applicable, that page also provides information on
where the material was incorporated.
Prior to 2003, several minor versions of the Unicode Standard were
published as Unicode Technical
Reports or as Unicode Standard Annexes. Such reports are listed in their own
the Technical Reports page. Instead of a direct link to the last approved document for those minor
versions, the reports page has a link to a page providing a summary for
that version of the Unicode Standard.
Errata to technical reports and other specifications may be
posted on the Updates and Errata page. To report errors in
published documents, such as the Unicode Standard or technical
reports, use the Unicode Consortium's contact form.