# Icuuc73.dll problem

**URL:** <https://forum.xojo.com/t/icuuc73-dll-problem/87598>\
**Category:** Windows\
**Created:** [January 30, 2026, 11:52am UTC](https://forum.xojo.com/t/icuuc73-dll-problem/87598 "2026-01-30T11:52:25Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Jeff\_Tullin](https://forum.xojo.com/user_avatar/forum.xojo.com/jeff_tullin/32/693_2.png) [@Jeff\_Tullin](https://forum.xojo.com/u/Jeff_Tullin)\
**Post date:** [January 30, 2026, 11:52am UTC](https://forum.xojo.com/t/icuuc73-dll-problem/87598/1 "2026-01-30T11:52:25Z")

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I have a customer who is reporting that icuuc73.dll causes an error under Windows 11

I’m compiling with Xojo 2024 r 2.1

Inno is set to **signonce** , so it shouldnt be changing the signature.

The file is dated 16 July 2024

Is there a newer one for Windows 11, or is Smart App being stupid?

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**Author:** ![Jeff\_Tullin](https://forum.xojo.com/user_avatar/forum.xojo.com/jeff_tullin/32/693_2.png) [@Jeff\_Tullin](https://forum.xojo.com/u/Jeff_Tullin)\
**Post date:** [January 30, 2026, 1:14pm UTC](https://forum.xojo.com/t/icuuc73-dll-problem/87598/2 "2026-01-30T13:14:12Z")

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I found this: **Key Information**

- 
  - **Function:** `icuuc.dll` (ICU Common DLL) provides core functionality for handling different languages, date formats, time zones, and other locale-specific data.

  - **Location:** The file is typically found in the `C:\Windows\System32\` directory.

  - **Version:** The specific version (73) refers to the version of the ICU libraries themselves, which are regularly updated by Microsoft as part of Windows updates.

  - **Compatibility:**

  - and so wonder why icuuc73 is shipping at all, if icu.dll could be used instead?

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<div class="post-metadata">

**Author:** ![AlbertoD](https://forum.xojo.com/letter_avatar_proxy/v4/letter/a/dbc845/32.png) [@AlbertoD](https://forum.xojo.com/u/AlbertoD)\
**Post date:** [January 30, 2026, 1:25pm UTC](https://forum.xojo.com/t/icuuc73-dll-problem/87598/3 "2026-01-30T13:25:47Z")

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> [@Jeff\_Tullin](#):
>
> wonder why icuuc73 is shipping at all, if icu.dll could be used instead?

> [@Jeff\_Tullin](#):
>
> I’m compiling with Xojo 2024 r 2.1

Because you are using Xojo 2024r2.1 and not 2025r1.1 or later.  
From the release notes: [Xojo 2025r1.1 Release Notes — Xojo documentation](https://documentation.xojo.com/resources/release_notes/2025r1.1.html)

> Windows built-in ICU Libraries: Eliminates manual ICU updates and reduces app file sizes.

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<div class="post-metadata">

**Author:** ![Jeff\_Tullin](https://forum.xojo.com/user_avatar/forum.xojo.com/jeff_tullin/32/693_2.png) [@Jeff\_Tullin](https://forum.xojo.com/u/Jeff_Tullin)\
**Post date:** [January 30, 2026, 4:25pm UTC](https://forum.xojo.com/t/icuuc73-dll-problem/87598/4 "2026-01-30T16:25:50Z")

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I’ll need to review how many people have late-patch level Windows 10

Probably safe to switch, but I’ll monitor.

My customer reports it works after a restart.