diff --git a/.github/workflows/validate-locales.yml b/.github/workflows/validate-locales.yml
new file mode 100644
index 0000000..4cd62be
--- /dev/null
+++ b/.github/workflows/validate-locales.yml
@@ -0,0 +1,34 @@
+name: Validate locales
+
+on:
+  pull_request:
+    paths:
+      - "_locales/**"
+      - "tools/validateLocalizationLengths.js"
+      - "package.json"
+      - ".github/workflows/validate-locales.yml"
+
+  push:
+    branches:
+      - main
+    paths:
+      - "_locales/**"
+      - "tools/validateLocalizationLengths.js"
+      - "package.json"
+      - ".github/workflows/validate-locales.yml"
+
+jobs:
+  validate-locales:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup Node
+        uses: actions/setup-node@v4
+        with:
+          node-version: 24
+
+      - name: Validate localization lengths
+        run: npm run lint:locales
diff --git a/package.json b/package.json
index 8c036c8..deb8146 100644
--- a/package.json
+++ b/package.json
@@ -3,6 +3,7 @@
     "chrome-types": "^0.1.349"
   },
   "scripts": {
+    "lint:locales": "node tools/validateLocalizationLengths.js",
     "prezip": "@powershell if (-not (Test-Path -Path \"./build/Release\")) {New-Item -ItemType Directory -Path \"./build/Release\"}",
     "zip": "bestzip ./build/Release/eq-toolkit_v1.7.0_unpackeged.zip resources/** scripts/** _locales/** manifest.json popup.html"
   },
diff --git a/tools/validateLocalizationLengths.js b/tools/validateLocalizationLengths.js
new file mode 100644
index 0000000..4ec0b8c
--- /dev/null
+++ b/tools/validateLocalizationLengths.js
@@ -0,0 +1,269 @@
+const fs = require("fs");
+const path = require("path");
+
+const LOCALES_DIR = path.join(__dirname, "..", "_locales");
+const FONT_SIZE_PX = 14;
+const TAMIL_CLUSTER_WIDTH_PX = 15;
+const TAMIL_WIDE_CLUSTER_WIDTH_PX = 18;
+const NARROW_LATIN_WIDTH_PX = 3;
+const NARROW_LATIN_T_WIDTH_PX = 4;
+
+const MESSAGE_LIMITS = {
+  empty_preset_name: {
+    maxWidthPx: 80,
+    maxLines: 1,
+    target: "#presets-toggle",
+  },
+  save_preset_button_label: {
+    maxWidthPx: 90,
+    maxLines: 2,
+    target: "#save-preset",
+  },
+  enable_eq_button_label: {
+    maxWidthPx: 90,
+    maxLines: 2,
+    target: "#change-eq",
+  },
+  stop_eq_button_label: {
+    maxWidthPx: 90,
+    maxLines: 2,
+    target: "#change-eq",
+  },
+  reset_button_label: {
+    maxWidthPx: 90,
+    maxLines: 2,
+    target: "#reset",
+  },
+};
+
+const CJK_OR_THAI_PATTERN =
+  /[\u3040-\u30ff\u3400-\u9fff\uac00-\ud7af\u0e00-\u0e7f]/u;
+const TAMIL_WIDE_VOWEL_SIGNS_PATTERN = /[\u0bc6-\u0bc8\u0bca-\u0bcc]/u;
+
+const SCRIPT_PATTERNS = {
+  arabic: /\p{Script=Arabic}/u,
+  bengali: /\p{Script=Bengali}/u,
+  cyrillic: /\p{Script=Cyrillic}/u,
+  devanagari: /\p{Script=Devanagari}/u,
+  ethiopic: /\p{Script=Ethiopic}/u,
+  greek: /\p{Script=Greek}/u,
+  gujarati: /\p{Script=Gujarati}/u,
+  han: /\p{Script=Han}/u,
+  hangul: /\p{Script=Hangul}/u,
+  hebrew: /\p{Script=Hebrew}/u,
+  hiragana: /\p{Script=Hiragana}/u,
+  kannada: /\p{Script=Kannada}/u,
+  katakana: /\p{Script=Katakana}/u,
+  latin: /\p{Script=Latin}/u,
+  malayalam: /\p{Script=Malayalam}/u,
+  tamil: /\p{Script=Tamil}/u,
+  telugu: /\p{Script=Telugu}/u,
+  thai: /\p{Script=Thai}/u,
+};
+
+const isScript = (char, script) => SCRIPT_PATTERNS[script].test(char);
+
+const canBreakAnywhere = (text) =>
+  SCRIPT_PATTERNS.han.test(text) || SCRIPT_PATTERNS.hangul.test(text);
+
+const g_segmenter =
+  typeof Intl.Segmenter === "function"
+    ? new Intl.Segmenter(undefined, { granularity: "grapheme" })
+    : null;
+
+const getTextUnits = (text) =>
+  g_segmenter
+    ? Array.from(g_segmenter.segment(text), (segment) => segment.segment)
+    : Array.from(text);
+
+const getCharWidth = (char) => {
+  if (/\p{Mark}/u.test(char)) return 0;
+  if (/\s/u.test(char)) return 4;
+
+  if (isScript(char, "han")) return FONT_SIZE_PX;
+  if (isScript(char, "hiragana") || isScript(char, "katakana")) return 12;
+  if (isScript(char, "hangul")) return 12;
+
+  if (isScript(char, "arabic")) return 7;
+  if (isScript(char, "hebrew")) return 7;
+  if (isScript(char, "ethiopic")) return 9;
+
+  if (isScript(char, "devanagari")) return 8;
+  if (isScript(char, "bengali")) return 8;
+  if (isScript(char, "gujarati")) return 8;
+  if (isScript(char, "kannada")) return 9;
+  if (isScript(char, "malayalam")) return 9;
+  if (isScript(char, "tamil")) return TAMIL_CLUSTER_WIDTH_PX;
+  if (isScript(char, "telugu")) return 9;
+  if (isScript(char, "thai")) return 8;
+
+  if (isScript(char, "latin") && /[iljI]/u.test(char)) {
+    return NARROW_LATIN_WIDTH_PX;
+  }
+  if (isScript(char, "latin") && char === "t") {
+    return NARROW_LATIN_T_WIDTH_PX;
+  }
+
+  if (isScript(char, "cyrillic")) return /[А-ЯЁ]/u.test(char) ? 9.5 : 7.5;
+  if (isScript(char, "greek")) return /[Α-Ω]/u.test(char) ? 8 : 7;
+  if (isScript(char, "latin")) return /[A-ZÀ-Þ]/u.test(char) ? 9 : 7;
+
+  if (/\p{Number}/u.test(char)) return 7;
+  if (/\p{Punctuation}/u.test(char) || /\p{Symbol}/u.test(char)) return 5;
+
+  return 8;
+};
+
+const getTextUnitWidth = (unit) => {
+  if (SCRIPT_PATTERNS.tamil.test(unit)) {
+    const baseWidth = Array.from(unit).reduce(
+      (sum, char) => sum + getCharWidth(char),
+      0
+    );
+
+    return TAMIL_WIDE_VOWEL_SIGNS_PATTERN.test(unit)
+      ? Math.max(baseWidth, TAMIL_WIDE_CLUSTER_WIDTH_PX)
+      : Math.max(baseWidth, TAMIL_CLUSTER_WIDTH_PX);
+  }
+
+  if (unit.length === 1) return getCharWidth(unit);
+
+  return Array.from(unit).reduce((sum, char) => sum + getCharWidth(char), 0);
+};
+
+const measureText = (text) =>
+  getTextUnits(text).reduce((sum, unit) => sum + getTextUnitWidth(unit), 0);
+
+const canBreakInside = (text) => CJK_OR_THAI_PATTERN.test(text);
+
+const getLinesForBreakableText = (text, maxWidthPx) => {
+  const lines = [];
+  let currentWidth = 0;
+
+  for (const unit of getTextUnits(text)) {
+    const unitWidth = getTextUnitWidth(unit);
+
+    if (currentWidth === 0 && /\s/u.test(unit)) continue;
+
+    if (currentWidth > 0 && currentWidth + unitWidth > maxWidthPx) {
+      lines.push(currentWidth);
+      currentWidth = 0;
+      if (/\s/u.test(unit)) continue;
+    }
+
+    currentWidth += unitWidth;
+  }
+
+  if (currentWidth > 0) lines.push(currentWidth);
+
+  return lines;
+};
+
+const getWrappedLineWidths = (message, maxWidthPx) => {
+  const trimmedMessage = message.trim();
+  if (trimmedMessage.length === 0) return [0];
+
+  if (canBreakAnywhere(trimmedMessage)) {
+    return getLinesForBreakableText(trimmedMessage, maxWidthPx);
+  }
+
+  if (!/\s/u.test(trimmedMessage)) {
+    return canBreakInside(trimmedMessage)
+      ? getLinesForBreakableText(trimmedMessage, maxWidthPx)
+      : [measureText(trimmedMessage)];
+  }
+
+  const words = trimmedMessage.split(/\s+/u);
+  const lines = [];
+  let currentWidth = 0;
+
+  for (const word of words) {
+    const wordWidth = measureText(word);
+    const separatorWidth = currentWidth === 0 ? 0 : getCharWidth(" ");
+    const nextWidth = currentWidth + separatorWidth + wordWidth;
+
+    if (nextWidth <= maxWidthPx) {
+      currentWidth = nextWidth;
+      continue;
+    }
+
+    if (currentWidth > 0) {
+      lines.push(currentWidth);
+      currentWidth = 0;
+    }
+
+    if (wordWidth <= maxWidthPx || !canBreakInside(word)) {
+      currentWidth = wordWidth;
+      continue;
+    }
+
+    lines.push(...getLinesForBreakableText(word, maxWidthPx));
+  }
+
+  if (currentWidth > 0) lines.push(currentWidth);
+
+  return lines;
+};
+
+const validateMessage = (locale, key, message, limit) => {
+  const lineWidths = getWrappedLineWidths(message, limit.maxWidthPx);
+  const widestLine = Math.max(...lineWidths);
+
+  if (lineWidths.length > limit.maxLines || widestLine > limit.maxWidthPx) {
+    return [
+      `${locale}: ${key} (${limit.target}) is too wide:`,
+      `  message: ${JSON.stringify(message)}`,
+      `  estimated lines: ${lineWidths.length}/${limit.maxLines}`,
+      `  widest line: ${widestLine}px/${limit.maxWidthPx}px`,
+    ].join("\n");
+  }
+
+  return null;
+};
+
+const readLocaleMessages = (locale) => {
+  const localePath = path.join(LOCALES_DIR, locale, "messages.json");
+  return JSON.parse(fs.readFileSync(localePath, "utf8"));
+};
+
+const validateLocale = (locale) => {
+  const messages = readLocaleMessages(locale);
+  const errors = [];
+
+  for (const [key, limit] of Object.entries(MESSAGE_LIMITS)) {
+    const entry = messages[key];
+
+    if (!entry || typeof entry.message !== "string") {
+      errors.push(`${locale}: ${key} must exist and contain a string message.`);
+      continue;
+    }
+
+    const error = validateMessage(locale, key, entry.message, limit);
+    if (error) errors.push(error);
+  }
+
+  return errors;
+};
+
+const main = () => {
+  const locales = fs
+    .readdirSync(LOCALES_DIR, { withFileTypes: true })
+    .filter((entry) => entry.isDirectory())
+    .map((entry) => entry.name)
+    .sort();
+
+  const errors = locales.flatMap(validateLocale);
+
+  if (errors.length > 0) {
+    console.error("Localization length validation failed.\n");
+    console.error(errors.join("\n\n"));
+    process.exitCode = 1;
+    return;
+  }
+
+  console.log(
+    `Localization length validation passed for ${locales.length} locales.`
+  );
+};
+
+main();