localization

This guide covers setting up and configuring Unity Localization, including locales, String and Asset Tables, Addressables integration, and CJK font support via Asset Tables.

0. Package Installation Check

Before doing anything else, verify that the Localization package is installed. Many APIs in this skill will fail silently or throw confusing errors if the package isn't present.

1. Check by reading the project, not by asking the Package Manager. Look for com.unity.localization in Packages/packages-lock.json. That file records what Unity actually resolved, it is plain JSON, and reading it needs no Editor and no async call. (Packages/manifest.json only records what was requested, so check the lock file.)
2. Install if missing: UnityEditor.PackageManager.Client.Add("com.unity.localization").
3. Wait properly. Client.Add and Client.List are asynchronous: they return a request that is still InProgress when the call returns, so reading the result in the same statement tells you nothing. Do not busy-wait on IsCompleted either; that blocks the main thread you are running on. Instead, return after firing the install, then poll packages-lock.json in a later call until the id appears. Installation also triggers a domain reload, so expect the first poll or two to fail; a fresh install typically resolves in a few seconds.
4. Confirm the types are actually loaded before using them, since the lock file can be written before the assemblies are ready:

   var t = System.Type.GetType(
       "UnityEngine.Localization.Settings.LocalizationSettings, Unity.Localization");
   return t != null ? "ready" : "not loaded yet";
   Only proceed once that returns ready.

1. Localization Settings & Locales

If LocalizationEditorSettings.ActiveLocalizationSettings is null, you must find or create it:

1. Find: Use AssetDatabase.FindAssets("t:LocalizationSettings", new[] { "Assets" }). If found, load the first one and assign it to LocalizationEditorSettings.ActiveLocalizationSettings.
   • Always pass the search folders. An unscoped FindAssets searches the whole project including read-only packages, so it can return an asset from a package and you end up pointing the project at something you cannot edit. This applies to every FindAssets call in this skill.
2. Create: If not found, create a new instance and save it to Assets/Localization/LocalizationSettings.asset. Use ScriptableObject.CreateInstance<LocalizationSettings>() followed by AssetDatabase.CreateAsset().
3. Activate: Set LocalizationEditorSettings.ActiveLocalizationSettings = settings.
4. Locales: Ensure locales (en, fr, de, etc.) exist. Create them if missing and add them to settings using LocalizationEditorSettings.AddLocale(locale).

2. Modifying Localization Tables

Programmatic changes to String or Asset tables require notification to the Editor. Always create the required asset tables, unless there is already an existing one in the project.

Safe Population Pattern

When populating tables from a dataset, match by Locale.Identifier.Code explicitly. The order of GetLocales() is not guaranteed to match your input data array — assuming it does will cause silent data mismatches that are very hard to debug. For Asset Tables, use the GUID of the asset: table.GetEntry(sharedId) ?? table.AddEntry(sharedId, guid);.

Refresh & Notification

After any modification (adding keys, updating values), notify the Editor so it can refresh its internal state. Skipping this will leave the Editor showing stale data until the next reimport.

1. Call EditorUtility.SetDirty(collection), EditorUtility.SetDirty(collection.SharedData), on each modified Table.
2. Unity 6+ Notification: LocalizationEditorSettings.EditorEvents.RaiseCollectionModified(sender, collection);
3. Always call AssetDatabase.SaveAssets() at the end.

3. UI Localization and Layout

Namespacing & Conflicts

• Always qualify names: Use UnityEngine.UI.Image, UnityEngine.UI.VerticalLayoutGroup, UnityEngine.UI.ScrollRect, UnityEngine.UI.Mask, UnityEngine.UI.CanvasScaler, UnityEngine.UI.GraphicRaycaster, UnityEngine.UI.ContentSizeFitter, UnityEngine.UI.LayoutRebuilder, etc.
• UnityEngine.UI is both a namespace and a class container, so unqualified names produce CS0118 (namespace used like a type). Full qualification avoids this entirely.
• Single Instance: Always check GameObject.Find("YourCanvasName") and destroy the old one before creating a new one.
• Locale switching: use the package, and keep preview and runtime separate. These are two different mechanisms, and conflating them is why locale switching often ends up hand-rolled.
  • To preview a locale while authoring, use the Localization Scene Controls window (Window > Asset Management > Localization Scene Controls). This is Editor-only. It is not a runtime feature, so it is not the answer when the game itself needs a language setting.
  • To switch locale at runtime, assign LocalizationSettings.SelectedLocale. That is the supported entry point, and everything bound through LocalizeStringEvent updates from it.
  • To pin which locale the game starts in, configure a startup locale selector on the Localization Settings asset. SpecificLocaleSelector is the one that forces a chosen locale; the default chain otherwise picks up the system language.
  • NEVER hand-roll locale state. A real in-game language menu is fine and expected, as long as it sets SelectedLocale and lets the package propagate the change. What is forbidden is a debug dropdown or menu that tracks its own "current language" variable, swaps strings itself, or reaches around the package, because nothing else in the project will follow it.

Localized String Events (Robust Binding)

• Check Component Type: Identify if the target is TextMeshPro or legacy UnityEngine.UI.Text.

• Bind Correctly: add the public UnityEngine.Localization.Components.LocalizeStringEvent component and wire it yourself — set StringReference to the table entry, then add an OnUpdateString listener that assigns the value to the text component (TMP_Text.text for TextMeshPro, UnityEngine.UI.Text.text for legacy Text).

  Do not reflect into UnityEditor.Localization.Plugins.TMPro.LocalizeComponent_TMPro or its UGUI counterpart. Those are internal (measured on Localization 1.5.12), so reaching them means routing around access control to reach an API Unity makes no stability commitment about — it can change or disappear in any package release. LocalizeStringEvent is public and does the same job with the wiring made explicit.

• Layout Rebuild: After setting localized text or populating a list, call UnityEngine.UI.LayoutRebuilder.ForceRebuildLayoutImmediate(parentTransform) to ensure dimensions update.

4. Asian Language Font Support (CJK)

Avoid TMP Fallback Fonts for CJK locales. Use Asset Table Font Swapping for each specific locale instead — fallbacks are unreliable and hard to debug when glyphs are missing.

Prerequisite: TMP Essential Resources must be imported

Check this before touching any TMP API. In a project that has never imported them, TMP_Settings.instance is null and TMP calls fail with a bare NullReferenceException that names nothing useful. TMP_FontAsset.CreateFontAsset is one of them, so font creation dies on the first line with an error that looks like a bug in your code.

// The check.
var ready = TMPro.TMP_Settings.instance != null;

If it is not ready, import them non-interactively:

// Do NOT use EditorApplication.ExecuteMenuItem("Window/TextMeshPro/Import TMP Essential Resources").
// It returns true and then opens a dialog that waits for a human, so nothing gets imported and the
// run appears to hang. Import the package directly instead.
string package = null;
var cache = System.IO.Path.GetFullPath(System.IO.Path.Combine(
    UnityEngine.Application.dataPath, "..", "Library", "PackageCache"));
foreach (var dir in System.IO.Directory.GetDirectories(cache))
{
    // TMP ships inside com.unity.ugui in Unity 6, and the folder name carries a version hash,
    // so search for the file rather than hardcoding a path.
    var candidate = System.IO.Path.Combine(dir, "Package Resources", "TMP Essential Resources.unitypackage");
    if (System.IO.File.Exists(candidate)) { package = candidate; break; }
}
UnityEditor.AssetDatabase.ImportPackage(package, false);   // false = non-interactive

Then poll TMP_Settings.instance != null in a later call, the same way as the package check in Step 0, and only continue once it is non-null. Verified on Unity 6000.5.8f1: the non-interactive import completes in a few seconds and the assets land in Assets/TextMesh Pro.

1. Use locale-specific fonts: Western fonts like Arial or Liberation Sans don't contain CJK glyphs, which results in "tofu" (square blocks). Always use a font designed for the target language:
   • For Simplified Chinese (zh-Hans): Use msyh.ttc (Microsoft YaHei) or equivalent.
   • For Japanese (ja): Use msgothic.ttc (MS Gothic) or equivalent.
   • For Korean (ko): Use malgun.ttf (Malgun Gothic) or equivalent.
   • If system font copying fails, stop and report it. Do not substitute with a Western font.
2. Robust Font Creation: Create dynamic TMP_FontAsset from imported fonts.
3. Multi-Atlas & Dynamic: CJK character sets are too large for static atlases; a single atlas will run out of space immediately.
   • fontAsset.atlasPopulationMode = AtlasPopulationMode.Dynamic;
   • fontAsset.isMultiAtlasTexturesEnabled = true;
4. Sub-Assets: add the atlas textures and the material. Adding only the texture is the usual mistake, and the material then never reaches the file at all: measured on Unity 6000.5.8f1, a font asset saved without the second call contains zero Material objects on disk, and one with it. A material that exists only in memory is not part of the asset, so anything that loads the asset fresh gets whatever TMP reconstructs rather than the material you configured, and any setting you applied to it is silently gone.

   // Every atlas texture, not just the first. Step 3 enabled multi-atlas, so there may be several.
   foreach (var atlas in fontAsset.atlasTextures)
   {
       UnityEditor.AssetDatabase.AddObjectToAsset(atlas, fontAsset);
   }
   // The material too. Without this line it is not written into the asset.
   UnityEditor.AssetDatabase.AddObjectToAsset(fontAsset.material, fontAsset);
   • Explicitly link the material's texture: fontAsset.material.mainTexture = fontAsset.atlasTexture; and set the font asset, its material, and its textures dirty before saving. (atlasTexture is the first entry of atlasTextures, which is what the primary material draws from, so this is consistent with adding every texture above.)
   • Verify against the file, not against the object you are holding. After AssetDatabase.SaveAssets(), call AssetDatabase.LoadAllAssetsAtPath(path) and confirm a Material is among the returned objects. Do not settle for fontAsset.material != null: that stays true whether or not the material was saved, because TMP will hand back an in-memory one, so it cannot tell a saved material from an unsaved one.
5. Addressables: Every asset referenced in an Asset Table must be marked as Addressable.
   • Do not reference assets inside a Resources/ folder in an Asset Table. This causes OperationException: Failed to load sub-asset errors. If an asset is in Resources/, copy it to Assets/Fonts/ or similar before making it Addressable.
   • If a font asset is deleted and recreated, the new GUID must be manually updated in the Asset Table and re-added to Addressables.
6. Specialized Types: For TextMesh Pro font swapping, prefer LocalizedTmpFont over LocalizedAsset<TMP_FontAsset> to avoid implicit conversion errors.
7. Build Requirement: After updating Asset Tables or Addressable groups, trigger a build: AddressableAssetSettings.BuildPlayerContent();.

Verification Step

Before concluding any CJK localization task:

1. The Tofu Check: Switch the editor locale to zh-Hans, ja, and ko. Inspect the UI. If any characters appear as squares (tofu), the font setup has FAILED.
2. Asset Table Check: Verify that the AssetTable for the CJK locale points to the correct CJK TMP_FontAsset, NOT a default Western font.
3. Multi-Atlas Check: Confirm isMultiAtlasTexturesEnabled is true on the CJK font assets.

5. Automatic Layout (UGUI)

• Parent: VerticalLayoutGroup with Child Control Height: True, Child Force Expand Height: False.
• Labels: Each label must have a ContentSizeFitter set to Vertical Fit: Preferred Size.
• TMP: Set Enable Word Wrapping: True and Overflow: Overflow.

Notes when translating an existing project

• Minimal Code Changes: Never modify code unrelated to localization. Use a static helper class (e.g., L10n) to wrap LocalizationSettings.StringDatabase.GetLocalizedString for easy injection into existing scripts.
• Robust Mapping Strategy: When mapping existing UI text to keys, sort keys by string length (descending) and match longest strings first. This prevents short strings (like "NO") from matching parts of longer sentences. Use case-insensitive matching where appropriate.
• Component Event Listeners: wire LocalizeStringEvent.OnUpdateString with UnityEventTools.AddPersistentListener, passing a delegate built over the text component's public text setter. The setter has no C# method-group name, so build the delegate by name: (UnityAction<string>)Delegate.CreateDelegate(typeof(UnityAction<string>), text, "set_text"). That is reflection over a public member, which is fine. See resources/L10nBatchProcessor.cs for the working version, including clearing any existing persistent listeners first so repeated runs don't stack duplicates.

  • Do not write the persistent-call fields directly through SerializedObject (m_MethodName, m_Mode, m_PersistentCalls). Those are private serialized names with no compatibility guarantee, and it isn't necessary: AddPersistentListener with the delegate above produces the same serialized call (target = the text component, method = set_text, mode = EventDefined).

  • You must then set the call state, or the label will not update in the Editor. AddPersistentListener leaves the call at UnityEventCallState.RuntimeOnly, so the binding is correct but dormant outside Play mode: switching locale in the Editor changes nothing, and it stays that way through a save and reload. Fix it with the public UnityEventBase.SetPersistentListenerState:

    UnityEventTools.AddPersistentListener(lse.OnUpdateString, setText);
    var index = lse.OnUpdateString.GetPersistentEventCount() - 1;
    lse.OnUpdateString.SetPersistentListenerState(
        index, UnityEngine.Events.UnityEventCallState.EditorAndRuntime);

    Verified on Unity 6000.5.8f1: without the second call the listener does not fire in Edit mode even after a prefab save and reload; with it the call state becomes EditorAndRuntime and the text updates immediately.

  • Persistent listeners MUST point to a method on a UnityEngine.Object; lambdas will fail.

  • Then confirm the binding is live, don't assume it. Wiring that looks right in the Inspector but does nothing is the characteristic failure of this step. All of the read-back you need is public API on the event, so none of this requires touching serialized fields:

    Check	Call	Expect
    Something was wired	GetPersistentEventCount()	> 0
    It points at the text component	GetPersistentTarget(i), GetPersistentMethodName(i)	the component, set_text
    It will fire while authoring	GetPersistentListenerState(i)	EditorAndRuntime
    It actually updates the label	lEvent.RefreshString()	the text value changes

    Do all four. A count above zero only proves something was wired, and a RuntimeOnly call fails the last check while being perfectly correct for a build, so reading the state is what tells a dormant binding apart from a broken one. A component that was added and configured but never fires is worse than an unlocalized label, because it reads as done.

• Initialization & Refresh:
  • LocalizationEditorSettings.CreateStringTableCollection expects a directory path (e.g., Assets/Localization), not a full asset path.
  • Always call lEvent.RefreshString() after assigning a LocalizedString reference programmatically to update the UI immediately.
  • Keys must exist with a non-empty value in every table of a collection (en, de, ja, …). A key that exists with an empty value is the common gap, and it is not silent: the package prints its own "No translation found for …" text into the game UI, so the shipped screen shows a developer message. Do not eyeball this. Run the completeness check below.
• Namespaces & Linq: Always include using System.Linq; when searching collections and using UnityEngine.Localization; when working with locales or tables.
• Verification: After modifying tables or addressables, run AddressableAssetSettings.BuildPlayerContent() and switch the Editor locale to verify changes. Check LocalizationSettings.Instance status after activation.

Table completeness check (run this before declaring the work done)

Enumerating the tables answers "did every key get a value in every locale" mechanically, so a missing entry is found before anyone plays the game. Run it and report the output.

var gaps = new System.Collections.Generic.List<string>();
var checkedCount = 0;
 
foreach (var col in UnityEditor.Localization.LocalizationEditorSettings.GetStringTableCollections())
{
    foreach (var key in col.SharedData.Entries)
    {
        foreach (var table in col.StringTables)
        {
            checkedCount++;
            var entry = table.GetEntry(key.Id);
            // A missing entry and a present-but-empty entry both show as untranslated in game.
            if (entry == null || string.IsNullOrWhiteSpace(entry.Value))
            {
                gaps.Add($"{col.TableCollectionName} / {table.LocaleIdentifier.Code} / {key.Key}");
            }
        }
    }
}
 
// Zero entries is not a pass. It means no collections or no locales were found, so the check
// examined nothing: report that distinctly instead of letting it read as success.
if (checkedCount == 0)
{
    return "INCONCLUSIVE: no table entries found. Either no String Table Collection exists yet, "
         + "or the collection has no locale tables. Fix that before trusting this check.";
}
 
return gaps.Count == 0
    ? $"COMPLETE: {checkedCount} entries checked, no gaps"
    : $"GAPS ({gaps.Count} of {checkedCount} checked):\n  " + string.Join("\n  ", gaps);

Verified on Unity 6000.5.8f1 against a table with one deliberately emptied ja value: it reports GAPS 1 of 4 naming exactly that entry, COMPLETE (4 checked) once the value is filled, and INCONCLUSIVE in a project with no tables.

Report the gap list rather than resolving it silently. Some gaps are decisions, not mistakes: a locale you were not asked to translate, or a key that is intentionally identical across languages. Filling those with the English text hides the decision. List them and let the user say which are intentional.

• Smart Strings: Set up smart strings where needed. Inspect the context of each string by taking the entire UI it is on, and any scripts that affect it, into account. Set the context on the string table to ensure translations make sense.

6. Recommended Translation Strategy

To efficiently translate an existing project, follow this multi-step workflow:

1. Extraction & Component Setup:

   • Find all occurrences. There are two separate hiding places, and scanning one misses the other.
     • Authored text sits on components in scenes and prefabs: legacy UnityEngine.UI.Text and TextMeshPro (TMP_Text, the base of TextMeshProUGUI and TextMeshPro). Walk both families. Measured on a real project: FindObjectsByType<Text> found 1 component while FindObjectsByType<TMP_Text> found 13, so a legacy-only pass reports success having done almost nothing.
     • Text composed in code never appears on a component at edit time, so no scene walk can see it. scoreLabel.text = $"EXP {value}" is invisible to every component-based scan and is the string that survives a "finished" localization pass. Find it in the C# instead:

       # Assignments and SetText calls that carry a string literal.
       grep -rnE '\.text\s*(=|\+=)\s*\$?"|SetText\(\s*\$?"' --include='*.cs' Assets/
       That pattern catches plain, interpolated, concatenated and += forms plus SetText, and deliberately does not match label.text = someVariable or label.text = Localize("KEY") (nothing to extract at the first, already routed at the second). Its blind spot is a literal held in a variable or const declared elsewhere; if the count looks low for the project, grep that file's string literals too.
   • Report what you did not convert. A composed string usually needs a smart string or a format argument, which is a judgment call, and some are genuinely not worth localizing. Whichever you choose, list every site the scan found alongside whether it was converted, and why not if it wasn't. Reporting "localized 24 strings" while nine found sites went untouched is the failure mode this list exists to prevent: the work looks finished and the gap only surfaces in a screenshot from another locale.
   • Shared Table: Create a central String Table (e.g., UIStrings) with the base language and a "Context" column for each key to guide translators.
   • Attach Components: For every UI element found, attach a LocalizeStringEvent (for text) and a LocalizedFont helper (for font swapping).
   • Validation: Ensure these components are set up with persistent listeners (EditorAndRuntime) so they update in the Editor immediately when the locale changes.

2. Context-Aware Translation:

   • Translate: Once the table is populated, provide translations for each locale.
   • Context is King: Always refer to the "Context" column or inspect the UI layout to ensure the translation fits the intended meaning and space.
   • Grammar & Tone: Ensure the tone matches the game's style. For example, use imperative verbs for buttons (e.g., German: "Lauf!" instead of "Laufen") and correct pluralization for labels (e.g., "Punkte" instead of "Punkt").

3. Quality Assurance (QA):

   • Scene Controls: Use Window > Asset Management > Localization Scene Controls or script: LocalizationSettings.SelectedLocale = LocalizationSettings.AvailableLocales.GetLocale("de");.
   • Visual Inspection: Methodically inspect every prefab and scene in the base language and all target languages.
   • Layout Fit: Check for text overflows or "tofu" (missing glyphs). Adjust font sizes or use ContentSizeFitter if strings are too long.

API Reference

For detailed API usage, common namespace conflicts, Addressables patterns, and font repair steps, see references/api-notes.md.

7. Accelerated Localization Workflow

To localize an entire project efficiently, use a batch processing script that handles all scenes in one pass.

Ask before acting: Before running any batch operation, confirm with the user:

"This will open every scene in the project, attach LocalizeStringEvent components, and save all modified scenes. This cannot be undone automatically. Shall I proceed?"

Only proceed once the user has confirmed. The batch processor template is in resources/L10nBatchProcessor.cs.

It walks both Text and TMP_Text, and LocalizeAll returns the labels it could not match (as scene :: object :: "text"). Print that list. It is the whole point of the return value: a run that wires 20 labels and silently leaves 9 alone looks identical to a complete one otherwise. The list covers authored text only, so pair it with the code scan in Section 6 and the table completeness check in Section 5.

Technical Tips for Speed

• Table References: Use TableReference names (strings) instead of GUIDs — they are easier to read and maintain.
• Batch Refresh: Use LocalizationSettings.Instance.ForceRefresh() after modifications to force the UI to update in the editor.
• Font Swap Automation: Create the GameAssets table once and use a script to re-assign LocalizeFontEvent to all labels in one pass.
• LocalizedFontAsset component: The template is in resources/LocalizedFontAsset.cs.