diff --git a/changelog.d/1336-traditional-chinese.md b/changelog.d/1336-traditional-chinese.md
index 386fd8ed4..c3969d44e 100644
--- a/changelog.d/1336-traditional-chinese.md
+++ b/changelog.d/1336-traditional-chinese.md
@@ -1,4 +1,4 @@
-- Add Traditional Chinese (zh-TW) with Taiwan terminology, language selection,
+- Add Traditional Chinese (zh-Hant) with language selection,
   and localized Chinese readouts. Based on translations by @caxer (#724),
   @tbdavid2019 (#652), @abiyeenzo (#914), and @EDIT-Aeterna (#979)
   (German, @gekh, #1336).
diff --git a/docs/CURRENT-STATE.md b/docs/CURRENT-STATE.md
index 69139e6bb..c3cbacba0 100644
--- a/docs/CURRENT-STATE.md
+++ b/docs/CURRENT-STATE.md
@@ -3583,7 +3583,7 @@ test:track` 43 tracking invariants · headless QA harnesses under
 
 ### Interface localization (October 2026)
 
-Shipped locales: **en** (source and fallback), **es**, **ru**, **zh-CN** and **zh-TW**. The code lives in
+Shipped locales: **en** (source and fallback), **es**, **ru**, **zh-CN** and **zh-Hant**. The code lives in
 `src/i18n/`. How to mark UI text: [`docs/I18N.md`](./I18N.md); translator workflow:
 [`docs/TRANSLATORS.md`](./TRANSLATORS.md).
 
@@ -3595,7 +3595,7 @@ Shipped locales: **en** (source and fallback), **es**, **ru**, **zh-CN** and **z
   `src/i18n/locales/<code>.json`, and a missing entry falls back to English.
 - **Locale choice.** `?lang=` → stored choice (`gev:locale:v1`) →
   `navigator.languages` → English. Chinese tags default to `zh-CN`; `Hant`, `TW`, `HK` and `MO`
-  select `zh-TW`. Explicit `Hans` selects `zh-CN` regardless of region. `?lang=` is not stored, and share links drop
+  select `zh-Hant`. Explicit `Hans` selects `zh-CN` regardless of region. `?lang=` is not stored, and share links drop
   it, so a recipient keeps their own language. The globe picker in the
   bottom-right corner (`src/ui/localePicker.js`) stores the choice, drops
   `?lang=` (keeps it only when storage is blocked) and reloads. It asks first
diff --git a/docs/TRANSLATORS.md b/docs/TRANSLATORS.md
index 5122afa9f..830ca155e 100644
--- a/docs/TRANSLATORS.md
+++ b/docs/TRANSLATORS.md
@@ -1,6 +1,6 @@
 # Translating God's Eye View
 
-Shipped languages: **English** (source and fallback), **Spanish** (`es`), **Russian** (`ru`), **Simplified Chinese** (`zh-CN`) and **Traditional Chinese** (`zh-TW`).
+Shipped languages: **English** (source and fallback), **Spanish** (`es`), **Russian** (`ru`), **Simplified Chinese** (`zh-CN`) and **Traditional Chinese** (`zh-Hant`).
 
 ## How it works
 
@@ -63,4 +63,4 @@ These are contracts, not copy: layer ids and registry keys, status enums and oth
 
 ## Language notes
 
-Each language keeps its glossary, plural forms, units and style in its own file, `docs/translations/<code>.md`: [Spanish](./translations/es.md), [Russian](./translations/ru.md), [Simplified Chinese](./translations/zh-CN.md), [Traditional Chinese](./translations/zh-TW.md). Read it before translating, and add a term there when you settle on one.
+Each language keeps its glossary, plural forms, units and style in its own file, `docs/translations/<code>.md`: [Spanish](./translations/es.md), [Russian](./translations/ru.md), [Simplified Chinese](./translations/zh-CN.md), [Traditional Chinese](./translations/zh-Hant.md). Read it before translating, and add a term there when you settle on one.
diff --git a/docs/translations/zh-Hant.md b/docs/translations/zh-Hant.md
new file mode 100644
index 000000000..9e3bbfeba
--- /dev/null
+++ b/docs/translations/zh-Hant.md
@@ -0,0 +1,36 @@
+# Traditional Chinese (`zh-Hant`)
+
+Catalog: `src/i18n/locales/zh-Hant.json`. General rules: [TRANSLATORS.md](../TRANSLATORS.md).
+
+Sources: caxer (#724), tbdavid2019 (#652), and the zh-CN catalog credited to abiyeenzo (#914) and EDIT-Aeterna (#979). The remaining entries were seeded with OpenCC s2twp and edited for consistency. The catalog retains terminology from these Taiwan-oriented sources; `zh-Hant` identifies the writing system and does not promise separate regional vocabulary.
+
+## Style
+
+- Use Traditional characters and consistent terminology from the glossary below. Prefer short, neutral instructions: 「點選地圖」、「儲存金鑰」.
+- Use full-width Chinese punctuation and 「」 for quotations. Keep `·`, `…`, provider names, codes and placeholders unchanged.
+- Separate Chinese from Latin letters and numbers with a space: 「AIS 船舶」、「24 小時」. Keep unit symbols unchanged: km, m, km/h, m/s, kn, ft, MW, °, %.
+- Chinese labels have no uppercase variant. Keep button labels short and avoid splitting short words across lines.
+- The picker displays 中文（繁體） / Chinese (Traditional). Browser tags with Hant or TW/HK/MO select the shared `zh-Hant` catalog. Existing `zh-TW` links and saved choices remain supported. Explicit Hans selects Simplified Chinese, including Hans-TW.
+
+## Plurals
+
+`Intl.PluralRules('zh-Hant')` uses only `other`. Keep suitable measure words: 「{count} 架飛機」、「{count} 艘船」、「{count} 個金鑰」.
+
+## Catalog terminology
+
+| English | Traditional Chinese |
+| --- | --- |
+| data / information | 資料 / 資訊 |
+| file / folder | 檔案 / 資料夾 |
+| settings / save | 設定 / 儲存 |
+| API key / token | API 金鑰 / 權杖 |
+| live / load | 即時 / 載入 |
+| camera / video | 攝影機 / 影片 |
+| network / link | 網路 / 連結 |
+| image / imagery | 圖像 / 影像 |
+| click / double-click | 點選 / 按兩下 |
+| response / timeout | 回應 / 逾時 |
+| layer / data layer | 圖層 / 資料圖層 |
+| cockpit / context | 駕駛艙 / 態勢 |
+| air quality | 空氣品質 |
+| transit / bikeshare | 大眾運輸 / 公共自行車 |
diff --git a/docs/translations/zh-TW.md b/docs/translations/zh-TW.md
deleted file mode 100644
index 8e25c8540..000000000
--- a/docs/translations/zh-TW.md
+++ /dev/null
@@ -1,36 +0,0 @@
-# Traditional Chinese (`zh-TW`)
-
-Catalog: `src/i18n/locales/zh-TW.json`. General rules: [TRANSLATORS.md](../TRANSLATORS.md).
-
-Sources: caxer (#724), tbdavid2019 (#652), and the zh-CN catalog credited to abiyeenzo (#914) and EDIT-Aeterna (#979). The remaining entries were seeded with OpenCC s2twp and edited for Taiwan usage.
-
-## Style
-
-- Use Traditional characters and Taiwan terminology. Prefer short, neutral instructions: 「點選地圖」、「儲存金鑰」.
-- Use full-width Chinese punctuation and 「」 for quotations. Keep `·`, `…`, provider names, codes and placeholders unchanged.
-- Separate Chinese from Latin letters and numbers with a space: 「AIS 船舶」、「24 小時」. Keep unit symbols unchanged: km, m, km/h, m/s, kn, ft, MW, °, %.
-- Chinese labels have no uppercase variant. Keep button labels short and avoid splitting short words across lines.
-- Browser tags with Hant or TW/HK/MO select this Taiwan catalog. Explicit Hans selects Simplified Chinese, including Hans-TW. This is not a separate Hong Kong localization.
-
-## Plurals
-
-`Intl.PluralRules('zh-TW')` uses only `other`. Keep suitable measure words: 「{count} 架飛機」、「{count} 艘船」、「{count} 個金鑰」.
-
-## Taiwan terminology
-
-| English              | Taiwan                | Mainland            |
-| -------------------- | --------------------- | ------------------- |
-| data / information   | 資料 / 資訊           | 数据 / 信息         |
-| file / folder        | 檔案 / 資料夾         | 文件 / 文件夹       |
-| settings / save      | 設定 / 儲存           | 设置 / 保存         |
-| API key / token      | API 金鑰 / 權杖       | API 密钥 / 令牌     |
-| live / load          | 即時 / 載入           | 实时 / 加载         |
-| camera / video       | 攝影機 / 影片         | 摄像头 / 视频       |
-| network / link       | 網路 / 連結           | 网络 / 链接         |
-| image / imagery      | 圖像 / 影像           | 图像 / 影像         |
-| click / double-click | 點選 / 按兩下         | 点击 / 双击         |
-| response / timeout   | 回應 / 逾時           | 响应 / 超时         |
-| layer / data layer   | 圖層 / 資料圖層       | 图层 / 数据图层     |
-| cockpit / context    | 駕駛艙 / 態勢         | 座舱 / 态势         |
-| air quality          | 空氣品質              | 空气质量            |
-| transit / bikeshare  | 大眾運輸 / 公共自行車 | 公共交通 / 共享单车 |
diff --git a/scripts/package-boundaries.json b/scripts/package-boundaries.json
index 4f88e858e..ae30a8c49 100644
--- a/scripts/package-boundaries.json
+++ b/scripts/package-boundaries.json
@@ -442,7 +442,7 @@
       "src/i18n/locales/es.json",
       "src/i18n/locales/ru.json",
       "src/i18n/locales/zh-CN.json",
-      "src/i18n/locales/zh-TW.json"
+      "src/i18n/locales/zh-Hant.json"
     ],
     "external": []
   },
@@ -469,7 +469,7 @@
       "src/i18n/locales/es.json",
       "src/i18n/locales/ru.json",
       "src/i18n/locales/zh-CN.json",
-      "src/i18n/locales/zh-TW.json"
+      "src/i18n/locales/zh-Hant.json"
     ],
     "external": ["cesium"]
   },
@@ -487,7 +487,7 @@
       "src/i18n/locales/es.json",
       "src/i18n/locales/ru.json",
       "src/i18n/locales/zh-CN.json",
-      "src/i18n/locales/zh-TW.json"
+      "src/i18n/locales/zh-Hant.json"
     ],
     "external": []
   },
@@ -517,7 +517,7 @@
       "src/i18n/locales/es.json",
       "src/i18n/locales/ru.json",
       "src/i18n/locales/zh-CN.json",
-      "src/i18n/locales/zh-TW.json",
+      "src/i18n/locales/zh-Hant.json",
       "src/ui/unitLabels.js",
       "src/ui/keyGuidance.js",
       "src/ui/statusText.js",
@@ -539,7 +539,7 @@
       "src/i18n/locales/es.json",
       "src/i18n/locales/ru.json",
       "src/i18n/locales/zh-CN.json",
-      "src/i18n/locales/zh-TW.json"
+      "src/i18n/locales/zh-Hant.json"
     ],
     "external": []
   },
@@ -556,7 +556,7 @@
       "src/i18n/locales/es.json",
       "src/i18n/locales/ru.json",
       "src/i18n/locales/zh-CN.json",
-      "src/i18n/locales/zh-TW.json"
+      "src/i18n/locales/zh-Hant.json"
     ],
     "external": []
   },
@@ -576,7 +576,7 @@
       "src/i18n/locales/es.json",
       "src/i18n/locales/ru.json",
       "src/i18n/locales/zh-CN.json",
-      "src/i18n/locales/zh-TW.json",
+      "src/i18n/locales/zh-Hant.json",
       "src/ui/unitLabels.js",
       "src/ui/statusBadge.js"
     ],
@@ -603,7 +603,7 @@
       "src/i18n/locales/es.json",
       "src/i18n/locales/ru.json",
       "src/i18n/locales/zh-CN.json",
-      "src/i18n/locales/zh-TW.json",
+      "src/i18n/locales/zh-Hant.json",
       "src/ui/layerNames.js"
     ],
     "external": []
@@ -638,7 +638,7 @@
       "src/i18n/locales/es.json",
       "src/i18n/locales/ru.json",
       "src/i18n/locales/zh-CN.json",
-      "src/i18n/locales/zh-TW.json",
+      "src/i18n/locales/zh-Hant.json",
       "src/ui/unitLabels.js"
     ],
     "external": ["cesium"]
@@ -655,7 +655,7 @@
       "src/i18n/locales/es.json",
       "src/i18n/locales/ru.json",
       "src/i18n/locales/zh-CN.json",
-      "src/i18n/locales/zh-TW.json",
+      "src/i18n/locales/zh-Hant.json",
       "src/ui/unitLabels.js"
     ],
     "external": []
@@ -811,7 +811,7 @@
       "src/i18n/locales/es.json",
       "src/i18n/locales/ru.json",
       "src/i18n/locales/zh-CN.json",
-      "src/i18n/locales/zh-TW.json",
+      "src/i18n/locales/zh-Hant.json",
       "src/ui/unitLabels.js",
       "src/ui/keyGuidance.js",
       "src/ui/layerNames.js",
@@ -932,7 +932,7 @@
       "src/i18n/locales/es.json",
       "src/i18n/locales/ru.json",
       "src/i18n/locales/zh-CN.json",
-      "src/i18n/locales/zh-TW.json",
+      "src/i18n/locales/zh-Hant.json",
       "src/ui/unitLabels.js"
     ],
     "external": ["cesium"]
@@ -999,7 +999,7 @@
       "src/i18n/locales/es.json",
       "src/i18n/locales/ru.json",
       "src/i18n/locales/zh-CN.json",
-      "src/i18n/locales/zh-TW.json",
+      "src/i18n/locales/zh-Hant.json",
       "src/ui/unitLabels.js"
     ],
     "external": ["cesium"]
@@ -1047,7 +1047,7 @@
       "src/i18n/locales/es.json",
       "src/i18n/locales/ru.json",
       "src/i18n/locales/zh-CN.json",
-      "src/i18n/locales/zh-TW.json"
+      "src/i18n/locales/zh-Hant.json"
     ],
     "external": ["cesium"]
   },
@@ -1109,7 +1109,7 @@
       "src/i18n/locales/es.json",
       "src/i18n/locales/ru.json",
       "src/i18n/locales/zh-CN.json",
-      "src/i18n/locales/zh-TW.json"
+      "src/i18n/locales/zh-Hant.json"
     ],
     "external": ["cesium"]
   },
@@ -1139,7 +1139,7 @@
       "src/i18n/locales/es.json",
       "src/i18n/locales/ru.json",
       "src/i18n/locales/zh-CN.json",
-      "src/i18n/locales/zh-TW.json",
+      "src/i18n/locales/zh-Hant.json",
       "src/ui/unitLabels.js",
       "src/layers/recentImagery/display.js"
     ],
@@ -1170,7 +1170,7 @@
       "src/i18n/locales/es.json",
       "src/i18n/locales/ru.json",
       "src/i18n/locales/zh-CN.json",
-      "src/i18n/locales/zh-TW.json"
+      "src/i18n/locales/zh-Hant.json"
     ],
     "external": ["cesium"]
   },
@@ -1202,7 +1202,7 @@
       "src/i18n/locales/es.json",
       "src/i18n/locales/ru.json",
       "src/i18n/locales/zh-CN.json",
-      "src/i18n/locales/zh-TW.json",
+      "src/i18n/locales/zh-Hant.json",
       "src/ui/unitLabels.js"
     ],
     "external": ["cesium", "satellite.js"]
@@ -1236,7 +1236,7 @@
       "src/i18n/locales/es.json",
       "src/i18n/locales/ru.json",
       "src/i18n/locales/zh-CN.json",
-      "src/i18n/locales/zh-TW.json"
+      "src/i18n/locales/zh-Hant.json"
     ],
     "external": ["cesium"]
   },
@@ -1279,7 +1279,7 @@
       "src/i18n/locales/es.json",
       "src/i18n/locales/ru.json",
       "src/i18n/locales/zh-CN.json",
-      "src/i18n/locales/zh-TW.json",
+      "src/i18n/locales/zh-Hant.json",
       "src/layers/installations/classLabel.js"
     ],
     "external": ["cesium", "@mapbox/vector-tile", "pbf"]
@@ -1315,7 +1315,7 @@
       "src/i18n/locales/es.json",
       "src/i18n/locales/ru.json",
       "src/i18n/locales/zh-CN.json",
-      "src/i18n/locales/zh-TW.json",
+      "src/i18n/locales/zh-Hant.json",
       "src/ui/unitLabels.js"
     ],
     "external": ["cesium"]
@@ -1366,7 +1366,7 @@
       "src/i18n/locales/es.json",
       "src/i18n/locales/ru.json",
       "src/i18n/locales/zh-CN.json",
-      "src/i18n/locales/zh-TW.json"
+      "src/i18n/locales/zh-Hant.json"
     ],
     "external": ["cesium", "pbf", "@mapbox/vector-tile"]
   },
@@ -1396,7 +1396,7 @@
       "src/i18n/locales/es.json",
       "src/i18n/locales/ru.json",
       "src/i18n/locales/zh-CN.json",
-      "src/i18n/locales/zh-TW.json"
+      "src/i18n/locales/zh-Hant.json"
     ],
     "external": ["cesium"]
   },
@@ -1445,7 +1445,7 @@
       "src/i18n/locales/es.json",
       "src/i18n/locales/ru.json",
       "src/i18n/locales/zh-CN.json",
-      "src/i18n/locales/zh-TW.json"
+      "src/i18n/locales/zh-Hant.json"
     ],
     "external": ["hls.js", "cesium"]
   },
@@ -1509,7 +1509,7 @@
       "src/i18n/locales/es.json",
       "src/i18n/locales/ru.json",
       "src/i18n/locales/zh-CN.json",
-      "src/i18n/locales/zh-TW.json",
+      "src/i18n/locales/zh-Hant.json",
       "src/layers/streetLevel/providers/mapillary/policy.js"
     ],
     "external": ["cesium", "pbf", "@mapbox/vector-tile", "mapillary-js"]
@@ -1539,7 +1539,7 @@
       "src/i18n/locales/es.json",
       "src/i18n/locales/ru.json",
       "src/i18n/locales/zh-CN.json",
-      "src/i18n/locales/zh-TW.json"
+      "src/i18n/locales/zh-Hant.json"
     ],
     "external": ["cesium", "@mapbox/vector-tile", "pbf"]
   },
@@ -1580,7 +1580,7 @@
       "src/i18n/locales/es.json",
       "src/i18n/locales/ru.json",
       "src/i18n/locales/zh-CN.json",
-      "src/i18n/locales/zh-TW.json"
+      "src/i18n/locales/zh-Hant.json"
     ],
     "external": ["cesium"]
   },
@@ -1603,7 +1603,7 @@
       "src/i18n/locales/es.json",
       "src/i18n/locales/ru.json",
       "src/i18n/locales/zh-CN.json",
-      "src/i18n/locales/zh-TW.json"
+      "src/i18n/locales/zh-Hant.json"
     ],
     "external": ["cesium"]
   },
@@ -1660,7 +1660,7 @@
       "src/i18n/locales/es.json",
       "src/i18n/locales/ru.json",
       "src/i18n/locales/zh-CN.json",
-      "src/i18n/locales/zh-TW.json"
+      "src/i18n/locales/zh-Hant.json"
     ],
     "external": ["cesium"]
   },
@@ -1717,7 +1717,7 @@
       "src/i18n/locales/es.json",
       "src/i18n/locales/ru.json",
       "src/i18n/locales/zh-CN.json",
-      "src/i18n/locales/zh-TW.json",
+      "src/i18n/locales/zh-Hant.json",
       "src/ui/statusText.js",
       "src/voice/providerCommands.js",
       "src/voice/providerCapabilities.js",
@@ -2582,7 +2582,7 @@
       "src/i18n/locales/es.json",
       "src/i18n/locales/ru.json",
       "src/i18n/locales/zh-CN.json",
-      "src/i18n/locales/zh-TW.json",
+      "src/i18n/locales/zh-Hant.json",
       "src/ui/unitLabels.js",
       "src/layers/recentImagery/display.js",
       "src/ui/keyGuidance.js",
@@ -3159,7 +3159,7 @@
       "src/i18n/locales/es.json",
       "src/i18n/locales/ru.json",
       "src/i18n/locales/zh-CN.json",
-      "src/i18n/locales/zh-TW.json",
+      "src/i18n/locales/zh-Hant.json",
       "src/ui/unitLabels.js",
       "src/layers/recentImagery/display.js",
       "src/layers/installations/classLabel.js",
@@ -3267,7 +3267,7 @@
       "src/i18n/locales/es.json",
       "src/i18n/locales/ru.json",
       "src/i18n/locales/zh-CN.json",
-      "src/i18n/locales/zh-TW.json",
+      "src/i18n/locales/zh-Hant.json",
       "src/i18n/index.js"
     ],
     "external": ["cesium"]
@@ -3290,7 +3290,7 @@
       "src/i18n/locales/es.json",
       "src/i18n/locales/ru.json",
       "src/i18n/locales/zh-CN.json",
-      "src/i18n/locales/zh-TW.json"
+      "src/i18n/locales/zh-Hant.json"
     ],
     "external": []
   },
@@ -3326,7 +3326,7 @@
       "src/i18n/locales/es.json",
       "src/i18n/locales/ru.json",
       "src/i18n/locales/zh-CN.json",
-      "src/i18n/locales/zh-TW.json"
+      "src/i18n/locales/zh-Hant.json"
     ],
     "external": ["cesium"]
   },
@@ -3351,7 +3351,7 @@
       "src/i18n/locales/es.json",
       "src/i18n/locales/ru.json",
       "src/i18n/locales/zh-CN.json",
-      "src/i18n/locales/zh-TW.json"
+      "src/i18n/locales/zh-Hant.json"
     ],
     "external": []
   },
@@ -3443,7 +3443,7 @@
       "src/i18n/locales/es.json",
       "src/i18n/locales/ru.json",
       "src/i18n/locales/zh-CN.json",
-      "src/i18n/locales/zh-TW.json",
+      "src/i18n/locales/zh-Hant.json",
       "src/ui/unitLabels.js"
     ],
     "external": ["cesium"]
@@ -3499,7 +3499,7 @@
       "src/i18n/locales/es.json",
       "src/i18n/locales/ru.json",
       "src/i18n/locales/zh-CN.json",
-      "src/i18n/locales/zh-TW.json",
+      "src/i18n/locales/zh-Hant.json",
       "src/ui/statusText.js",
       "src/voice/providerCapabilities.js"
     ],
@@ -3754,7 +3754,7 @@
       "src/i18n/locales/es.json",
       "src/i18n/locales/ru.json",
       "src/i18n/locales/zh-CN.json",
-      "src/i18n/locales/zh-TW.json"
+      "src/i18n/locales/zh-Hant.json"
     ],
     "external": ["cesium", "egm96-universal", "pbf"]
   },
@@ -3798,7 +3798,7 @@
       "src/i18n/locales/es.json",
       "src/i18n/locales/ru.json",
       "src/i18n/locales/zh-CN.json",
-      "src/i18n/locales/zh-TW.json"
+      "src/i18n/locales/zh-Hant.json"
     ],
     "external": ["cesium", "pbf"]
   },
@@ -3852,7 +3852,7 @@
       "src/i18n/locales/es.json",
       "src/i18n/locales/ru.json",
       "src/i18n/locales/zh-CN.json",
-      "src/i18n/locales/zh-TW.json"
+      "src/i18n/locales/zh-Hant.json"
     ],
     "external": ["cesium"]
   },
@@ -3869,7 +3869,7 @@
       "src/i18n/locales/es.json",
       "src/i18n/locales/ru.json",
       "src/i18n/locales/zh-CN.json",
-      "src/i18n/locales/zh-TW.json",
+      "src/i18n/locales/zh-Hant.json",
       "src/ui/statusText.js",
       "src/ui/layerNames.js"
     ],
@@ -4063,7 +4063,7 @@
       "src/i18n/locales/es.json",
       "src/i18n/locales/ru.json",
       "src/i18n/locales/zh-CN.json",
-      "src/i18n/locales/zh-TW.json",
+      "src/i18n/locales/zh-Hant.json",
       "src/ui/statusText.js",
       "src/ui/layerNames.js"
     ],
diff --git a/src/i18n/firms-live-zh.test.mjs b/src/i18n/firms-live-zh.test.mjs
index 9698d5dd6..11878e790 100644
--- a/src/i18n/firms-live-zh.test.mjs
+++ b/src/i18n/firms-live-zh.test.mjs
@@ -36,7 +36,7 @@ for (const [age, zh, en, tw] of cases) {
       assert.equal(methods.getStats().loadingLabel, `LIVE · updated ${en}`);
       setLocale('zh-CN');
       assert.equal(methods.getStats().loadingLabel, `实时 · 更新于 ${zh}`);
-      setLocale('zh-TW');
+      setLocale('zh-Hant');
       assert.equal(methods.getStats().loadingLabel, `即時 · 更新於 ${tw}`);
     } finally {
       setLocale(previousLocale);
diff --git a/src/i18n/i18n.test.mjs b/src/i18n/i18n.test.mjs
index 87eeed24a..031d4f85e 100644
--- a/src/i18n/i18n.test.mjs
+++ b/src/i18n/i18n.test.mjs
@@ -39,12 +39,14 @@ test('normalizeLocale folds regional variants and rejects unshipped tags', () =>
   assert.equal(normalizeLocale('zh'), 'zh-CN');
   assert.equal(normalizeLocale('zh-CN'), 'zh-CN');
   assert.equal(normalizeLocale('zh-Hans-SG'), 'zh-CN');
-  assert.equal(normalizeLocale('zh-TW'), 'zh-TW');
-  assert.equal(normalizeLocale('zh-Hant-HK'), 'zh-TW');
+  assert.equal(normalizeLocale('zh-Hant'), 'zh-Hant');
+  assert.equal(normalizeLocale(' ZH_hant '), 'zh-Hant');
+  assert.equal(normalizeLocale('zh-TW'), 'zh-Hant');
+  assert.equal(normalizeLocale('zh-Hant-HK'), 'zh-Hant');
   assert.equal(normalizeLocale('zh-Hans-TW'), 'zh-CN');
-  assert.equal(normalizeLocale('zh-Hant-CN'), 'zh-TW');
-  assert.equal(normalizeLocale('zh_HK'), 'zh-TW');
-  assert.equal(normalizeLocale('zh-MO'), 'zh-TW');
+  assert.equal(normalizeLocale('zh-Hant-CN'), 'zh-Hant');
+  assert.equal(normalizeLocale('zh_HK'), 'zh-Hant');
+  assert.equal(normalizeLocale('zh-MO'), 'zh-Hant');
   assert.equal(normalizeLocale(undefined), null);
 });
 
diff --git a/src/i18n/index.js b/src/i18n/index.js
index 84776e7dd..6fc4becc9 100644
--- a/src/i18n/index.js
+++ b/src/i18n/index.js
@@ -19,9 +19,9 @@ import {
 import es from './locales/es.json' with { type: 'json' };
 import ru from './locales/ru.json' with { type: 'json' };
 import zhCN from './locales/zh-CN.json' with { type: 'json' };
-import zhTW from './locales/zh-TW.json' with { type: 'json' };
+import zhHant from './locales/zh-Hant.json' with { type: 'json' };
 
-const CATALOGS = Object.freeze({ es, ru, 'zh-CN': zhCN, 'zh-TW': zhTW });
+const CATALOGS = Object.freeze({ es, ru, 'zh-CN': zhCN, 'zh-Hant': zhHant });
 
 let currentLocale = DEFAULT_LOCALE;
 
diff --git a/src/i18n/locale.js b/src/i18n/locale.js
index 4efd4f589..55ed71163 100644
--- a/src/i18n/locale.js
+++ b/src/i18n/locale.js
@@ -8,15 +8,15 @@ export const LOCALE_STORAGE_KEY = 'gev:locale:v1';
 export const DEFAULT_LOCALE = 'en';
 
 /** Shipped locales; order does not matter. Adding one: docs/TRANSLATORS.md. */
-export const LOCALES = Object.freeze(['en', 'es', 'ru', 'zh-CN', 'zh-TW']);
+export const LOCALES = Object.freeze(['en', 'es', 'ru', 'zh-CN', 'zh-Hant']);
 
 /** Each locale named in its own language, for the selector. */
 export const LOCALE_NAMES = Object.freeze({
   en: 'English',
   es: 'Español',
   ru: 'Русский',
-  'zh-CN': '简体中文',
-  'zh-TW': '繁體中文',
+  'zh-CN': '中文（简体）',
+  'zh-Hant': '中文（繁體）',
 });
 
 /** Right-to-left locales. */
@@ -24,7 +24,8 @@ const RTL_LOCALES = Object.freeze([]);
 
 /**
  * Map any language tag to a shipped locale: 'ru-RU' and 'RU' → 'ru',
- * 'zh', 'zh-CN' and 'zh-Hans-SG' → 'zh-CN'.
+ * 'zh', 'zh-CN' and 'zh-Hans-SG' → 'zh-CN';
+ * 'zh-Hant', 'zh-TW', 'zh-HK' and 'zh-MO' → 'zh-Hant'.
  * @returns {string|null}
  */
 export function normalizeLocale(candidate) {
@@ -33,7 +34,7 @@ export function normalizeLocale(candidate) {
   if (primary === 'zh') {
     if (rest.includes('hans')) return 'zh-CN';
     return rest.some((part) => ['hant', 'tw', 'hk', 'mo'].includes(part))
-      ? 'zh-TW'
+      ? 'zh-Hant'
       : 'zh-CN';
   }
   return LOCALES.includes(primary) ? primary : null;
diff --git a/src/i18n/locales/zh-TW.json b/src/i18n/locales/zh-Hant.json
similarity index 100%
rename from src/i18n/locales/zh-TW.json
rename to src/i18n/locales/zh-Hant.json
diff --git a/src/i18n/same-as-english.json b/src/i18n/same-as-english.json
index 48688a0c7..d96319535 100644
--- a/src/i18n/same-as-english.json
+++ b/src/i18n/same-as-english.json
@@ -193,7 +193,7 @@
     "ΔN",
     "▲ {frp} MW"
   ],
-  "zh-TW": [
+  "zh-Hant": [
     "1090 MHz",
     "978 MHz UAT",
     "AIS: --",
diff --git a/src/i18n/zh-TW-display.test.mjs b/src/i18n/zh-Hant-display.test.mjs
similarity index 72%
rename from src/i18n/zh-TW-display.test.mjs
rename to src/i18n/zh-Hant-display.test.mjs
index 74b2f714a..187977cb3 100644
--- a/src/i18n/zh-TW-display.test.mjs
+++ b/src/i18n/zh-Hant-display.test.mjs
@@ -1,7 +1,12 @@
 import test from 'node:test';
 import assert from 'node:assert/strict';
 import { setLocale, t, tn, getLocale } from './index.js';
-import { resolveLocale, LOCALE_STORAGE_KEY } from './locale.js';
+import {
+  resolveLocale,
+  LOCALE_STORAGE_KEY,
+  writeStoredLocale,
+  applyDocumentLanguage,
+} from './locale.js';
 import { hudQuantity, LOCALIZED_LOCALITY } from '../hudLocalityFormat.js';
 import { formatCockpitDistance } from '../ui/cockpitPresentation.js';
 import { READOUT_WORDS } from '../layers/recentImagery/display.js';
@@ -14,7 +19,7 @@ test('Traditional Chinese resolves from URL, saved preference and browser langua
       storage: { getItem: () => 'en' },
       languages: ['en'],
     }),
-    'zh-TW',
+    'zh-Hant',
   );
   assert.equal(
     resolveLocale({
@@ -24,7 +29,7 @@ test('Traditional Chinese resolves from URL, saved preference and browser langua
       },
       languages: ['en'],
     }),
-    'zh-TW',
+    'zh-Hant',
   );
   assert.equal(
     resolveLocale({
@@ -32,14 +37,29 @@ test('Traditional Chinese resolves from URL, saved preference and browser langua
       storage: { getItem: () => null },
       languages: ['zh-Hant', 'en'],
     }),
-    'zh-TW',
+    'zh-Hant',
   );
 });
 
+test('Traditional Chinese persists and exposes the script locale for legacy choices', () => {
+  const stored = new Map();
+  assert.equal(
+    writeStoredLocale('zh-TW', {
+      setItem: (key, value) => stored.set(key, value),
+    }),
+    true,
+  );
+  assert.equal(stored.get(LOCALE_STORAGE_KEY), 'zh-Hant');
+  const doc = { documentElement: {} };
+  assert.equal(applyDocumentLanguage(doc, 'zh-TW'), true);
+  assert.equal(doc.documentElement.lang, 'zh-Hant');
+  assert.equal(doc.documentElement.dir, 'ltr');
+});
+
 test('Traditional Chinese readouts preserve unit case, coordinates and natural relative dates', () => {
   const previous = getLocale();
   try {
-    setLocale('zh-TW');
+    setLocale('zh-Hant');
     assert.equal(hudQuantity(2069, 'km', 1), '2069.0 km');
     assert.equal(formatCockpitDistance(14000), '14\u00a0km');
     assert.equal(
diff --git a/src/ui/localePicker.js b/src/ui/localePicker.js
index d60b4e91a..41875042d 100644
--- a/src/ui/localePicker.js
+++ b/src/ui/localePicker.js
@@ -20,6 +20,11 @@ export const LOCALE_SEARCH_THRESHOLD = 8;
 /** Type-ahead keystrokes closer together than this extend one prefix. */
 export const TYPEAHEAD_RESET_MS = 500;
 
+const CHINESE_LABELS = {
+  'zh-CN': 'Chinese (Simplified)',
+  'zh-Hant': 'Chinese (Traditional)',
+};
+
 /**
  * Text folded for search: no diacritics, lower case. 'Español' → 'espanol',
  * 'Ёжик' → 'ежик'.
@@ -464,12 +469,13 @@ export function mountLocalePicker({
     item.dataset.locale = option.code;
     const name = element(documentRef, 'span', 'locale-picker-native');
     name.textContent = option.nativeName;
-    // Every row reads the same: the language named in itself, then its code.
-    // The interface-language name only helps the search find it.
+    // Chinese variants are distinguished by script rather than region.
     const meta = element(documentRef, 'span', 'locale-picker-meta');
     const codeLabel = element(documentRef, 'span', 'locale-picker-option-code');
     codeLabel.setAttribute('translate', 'no');
-    codeLabel.textContent = option.code.toUpperCase();
+    codeLabel.textContent =
+      CHINESE_LABELS[option.code] || option.code.toUpperCase();
+    if (CHINESE_LABELS[option.code]) codeLabel.lang = 'en';
     meta.append(codeLabel);
     const text = element(documentRef, 'span', 'locale-picker-text');
     text.append(name, meta);
diff --git a/src/ui/localePicker.test.mjs b/src/ui/localePicker.test.mjs
index 5151ad4fc..057642827 100644
--- a/src/ui/localePicker.test.mjs
+++ b/src/ui/localePicker.test.mjs
@@ -40,7 +40,7 @@ test('the current language comes first, the rest by their own names', () => {
         nativeNames: LOCALE_NAMES,
       }),
     ),
-    ['ru', 'en', 'es', 'zh-CN', 'zh-TW'],
+    ['ru', 'en', 'es', 'zh-CN', 'zh-Hant'],
   );
   assert.deepEqual(
     codes(
@@ -50,7 +50,7 @@ test('the current language comes first, the rest by their own names', () => {
         nativeNames: LOCALE_NAMES,
       }),
     ),
-    ['es', 'en', 'ru', 'zh-CN', 'zh-TW'],
+    ['es', 'en', 'ru', 'zh-CN', 'zh-Hant'],
   );
   assert.deepEqual(
     codes(
@@ -60,7 +60,7 @@ test('the current language comes first, the rest by their own names', () => {
         nativeNames: LOCALE_NAMES,
       }),
     ),
-    ['en', 'es', 'ru', 'zh-CN', 'zh-TW'],
+    ['en', 'es', 'ru', 'zh-CN', 'zh-Hant'],
   );
   const rows = buildLocaleOptions({
     locales: MANY,
@@ -263,7 +263,7 @@ test('keyboard model: open on the current language, move, choose, close', () =>
   assert.deepEqual(model.keydown({ key: 'ArrowDown' }), { handled: true });
   assert.equal(model.activeOption.code, 'en');
   model.keydown({ key: 'End' });
-  assert.equal(model.activeOption.code, 'zh-TW');
+  assert.equal(model.activeOption.code, 'zh-Hant');
   model.keydown({ key: 'Home' });
   assert.equal(model.activeOption.code, 'ru');
   model.keydown({ key: 'ArrowUp' });