Corrigenda to the Unicode Standard
The Table of Corrigenda shows the complete list of formal corrigenda to
the Unicode Standard. See also the list
of current Updates and Errata.
The table lists each corrigendum on the left and then states the
relevant information about that corrigendum. The column with the
effective date also lists the Unicode Technical Committee action and/or
Public Review Issue (PRI) that led to its creation in brackets following
The applicable versions column lists the range of Unicode versions
relevant to a particular corrigendum. An implementation claiming
conformance to any version of Unicode in that range may also claim
conformance to one or more of the corrigenda applicable to that version.
References to versions with applied corrigenda can be made as shown at
Corrigenda are fixed in the Unicode Standard at the first available release opportunity. For each corrigendum, the Unicode version in which it was fixed and the date of the release of that version are also shown in the table.
Implementations which claim conformance to that fixed version (or later) need not separately reference a corrigendum, as the error has already been corrected in the
The final column in the table lists the relevant chapter, Unicode Standard Annex
(UAX), or data file from the Unicode Character Database where the results of the correction
Each version of the Unicode Standard, once published, is absolutely
stable and will never change. Implementations or specifications
that refer to a specific version of the Unicode Standard can
rely upon this stability. However, if those implementations or
specifications are upgraded to a later version of the Unicode
Standard, then of course some changes may be necessary to
account for changes in Unicode between versions: addition of
new characters, addition of new properties, specification of
new algorithms, and so on.
Occasionally an error is found in a particular version of the Unicode Standard which is of sufficient importance that the UTC issues a formal corrigendum notice, prior to the release of the subsequent version of the
standard. Corrigenda are limited in number; the entire list of such notices is specified in the table on this page.
A formal corrigendum notice does not change the contents of any previously published versions of the standard. Instead, it provides a mechanism whereby an implementation, protocol, or other standard can cite or claim conformance to an existing version of the Unicode Standard with the corrigendum applied.
This may be required in particular instances when an implementation, protocol, or standard otherwise supports a particular version of the Unicode Standard, but for security or interoperability reasons must apply a particular critical fix.
In a reference or claim of conformance to a particular version of the Unicode Standard, if the citation does not specifically mention a corrigendum, then the corrigendum does not apply for that reference or conformance claim.
All corrigenda must be in compliance with the
Character Encoding Stability Policy.
Corrigenda are reviewed and approved by the Unicode Consortium officers to
ensure compliance with that policy. See also the
FAQ on Normalization for more information about stability considerations and normalization.
In some instances, particularly for protocols making use of Unicode normalization, an implementation may have requirements to maintain complete stability in an algorithm. This may extend even to the retention of known errors and the non-application of corrigenda.
The file NormalizationCorrections.txt in the Unicode Character Database was introduced to assist in maintaining stability for implementations, by clearly identifying any data changes impacting normalization, with the exact changes in decomposition mappings and the exact versions for the changes. Any corrigendum to the Unicode Standard which changes a decomposition mapping in any way is then also reflected into NormalizationCorrections.txt, so that an implementation can track the exact status of any such changes. An implementer can then either apply the corrigendum to an earlier version of the standard (the normal case), or can choose
not to apply the results of the corrigendum when moving an implementation forward to a later version of the standard (the exceptional case).
Implementers should be cautious when choosing the latter option, as it puts them formally out of compliance with later versions of the Unicode Standard and reduces their interoperability with implementations that have upgraded to later versions. However, in limited contexts where the overriding concern is backwards compatibility in the protocol itself, maintenance of an older, uncorrected form of Unicode normalization might be warranted.
Where possible, however, implementers are encouraged to adopt the most up-to-date and correct version of the Unicode Standard compatible with their application needs.