ICU 78.3 Released — and future changes

[Markus Scherer]

Dear friends and users of ICU,

We are pleased to announce the release of Unicode® ICU 78.3.

This is a maintenance update on top of ICU 78 and 78.2, mostly for the CLDR 48.2 bug fixes. In addition, it fixes a C++ code point iterator bug, and updates to timezone data 2026a.

• Details: ICU 78

• Download: releases/tag/release-78.3

• Maven: com.ibm.icu / icu4j / version 78.3

The next major release of ICU will be ICU 79, planned for October. It will update to CLDR 49 and Unicode 18.

Attention: Future Changes

Beginning with ICU 79 (October 2026), ICU will be making some significant changes to its API.  Please follow the ticket links below for details and to offer comments:

1. We are planning to declare as final C++ classes (such as UnicodeString) that have long been documented as “not suitable for subclassing”. (These are all APIs that existed long before C++ had the final keyword). This change will make the API more resilient, but will break users who have created unsupported subclasses.
   See ICU-23284.

2. CLDR is deprecating the unusual H24 hour cycle, and ICU will change the behavior of H24 to match that of H23. See CLDR-18303.

3. CLDR is removing data and display names for Japanese eras before Meiji. Pre-Meiji dates will be displayed using the Gregorian calendar. See CLDR-11400.

4. CLDR is making the week-of-year numbering always follow ISO rules. See CLDR-18275.

Best regards,

Markus Scherer for the ICU Project