diff --git a/src/locales/ar.json b/src/locales/ar.json
index 907920f12d2..7370a51f63e 100644
--- a/src/locales/ar.json
+++ b/src/locales/ar.json
@@ -197,7 +197,7 @@
 	"timeslider.month.october": "أكتوبر",
 	"timeslider.month.november": "نوفمبر",
 	"timeslider.month.december": "ديسمبر",
-	"timeslider.unnamedauthors": "بدون اسم {{num}} {[plural(num) واحد: كاتب، آخر: مؤلف]}",
+	"timeslider.unnamedauthors": "بدون اسم {{num}} {[plural(num) one: كاتب, other: مؤلف ]}",
 	"pad.savedrevs.marked": "هذا التنقيح محدد الآن كمراجعة محفوظة",
 	"pad.savedrevs.timeslider": "يمكنك عرض المراجعات المحفوظة بزيارة متصفح التاريخ",
 	"pad.userlist.entername": "أدخل اسمك",
diff --git a/src/locales/diq.json b/src/locales/diq.json
index 0886872f8cb..49bd7e2ee2a 100644
--- a/src/locales/diq.json
+++ b/src/locales/diq.json
@@ -159,7 +159,7 @@
 	"timeslider.month.october": "Tışrino Verên",
 	"timeslider.month.november": "Tışrino Peyên",
 	"timeslider.month.december": "Kanun",
-	"timeslider.unnamedauthors": "{{num}} unnamed {[plural(num) zu: nuştoğ, zewbi: nustoği ]}",
+	"timeslider.unnamedauthors": "{{num}} unnamed {[plural(num) one: nuştoğ, other: nustoği ]}",
 	"pad.savedrevs.marked": "Eno vurriyayış henda qeyd bıyaye yew vurriyayış deyne nışan bıyo",
 	"pad.savedrevs.timeslider": "Xızberê zemani ziyer kerdış ra şıma şenê revizyonanê qeyd bıyayan bıvinê",
 	"pad.userlist.entername": "Namey xo cıkewe",
diff --git a/src/locales/ff.json b/src/locales/ff.json
index a1164036d37..e2fd32a1ffd 100644
--- a/src/locales/ff.json
+++ b/src/locales/ff.json
@@ -147,7 +147,7 @@
 	"timeslider.month.october": "Yarkomaa",
 	"timeslider.month.november": "Jolal",
 	"timeslider.month.december": "Bowte",
-	"timeslider.unnamedauthors": "{{num}} innitaaka {[plural(num) goo: ballifo, goɗɗo: wallifɓe]}",
+	"timeslider.unnamedauthors": "{{num}} innitaaka {[plural(num) one: ballifo, other: wallifɓe ]}",
 	"pad.savedrevs.marked": "Ndee yamre maantaama jooni ko baylital danndangal",
 	"pad.savedrevs.timeslider": "Aɗa waawi yiyde baylitte danndaaɗe so yillaade daasorde tuma ndee",
 	"pad.userlist.entername": " Naatnu innde maa",
diff --git a/src/locales/hr.json b/src/locales/hr.json
index 3111f7e3a5e..4aad1692995 100644
--- a/src/locales/hr.json
+++ b/src/locales/hr.json
@@ -115,7 +115,7 @@
 	"timeslider.month.october": "listopada",
 	"timeslider.month.november": "studenoga",
 	"timeslider.month.december": "prosinca",
-	"timeslider.unnamedauthors": "{{num}} {[plural(num) one: neimenovani autor, plural(num) two: neimenovana autora, plural(num) other: neimenovanih autora ]}",
+	"timeslider.unnamedauthors": "{{num}} {[plural(num) one: neimenovani autor, two: neimenovana autora, other: neimenovanih autora ]}",
 	"pad.savedrevs.marked": "Ova inačica označena je sada kao spremljena inačica",
 	"pad.savedrevs.timeslider": "Možete vidjeti spremljene inačice rabeći vremensku lentu (timeslider)",
 	"pad.userlist.entername": "Unesite Vaše suradničko ime",
diff --git a/src/locales/hu.json b/src/locales/hu.json
index 89de739c95d..484ec77a1ab 100644
--- a/src/locales/hu.json
+++ b/src/locales/hu.json
@@ -158,7 +158,7 @@
 	"timeslider.month.october": "október",
 	"timeslider.month.november": "november",
 	"timeslider.month.december": "december",
-	"timeslider.unnamedauthors": "{{num}} névtelen {[plural(num), one: szerző, other: szerző]}",
+	"timeslider.unnamedauthors": "{{num}} névtelen {[plural(num) one: szerző, other: szerző ]}",
 	"pad.savedrevs.marked": "Ez a revízió mostantól mentettként jelölve",
 	"pad.savedrevs.timeslider": "A mentett revíziókat az időcsúszkán tudod megnézni",
 	"pad.userlist.entername": "Add meg a nevedet",
diff --git a/src/locales/it.json b/src/locales/it.json
index 13dd100f0ba..37586bc8c0e 100644
--- a/src/locales/it.json
+++ b/src/locales/it.json
@@ -395,7 +395,7 @@
 	"pad.savedrevs.timeslider": "Puoi vedere le versioni salvate visitando la cronologia",
 	"pad.userlist.entername": "Inserisci il tuo nome",
 	"pad.userlist.unnamed": "senza nome",
-	"pad.userlist.onlineCount": "{[ plurale(count) uno: {{count}} utente connesso, altro: {{count}} utenti connessi ]}",
+	"pad.userlist.onlineCount": "{[ plural(count) one: {{count}} utente connesso, other: {{count}} utenti connessi ]}",
 	"pad.editbar.clearcolors": "Eliminare i colori degli autori sull'intero documento? Questa azione non può essere annullata",
 	"pad.impexp.importbutton": "Importa ora",
 	"pad.impexp.importing": "Importazione in corso...",
diff --git a/src/locales/mnw.json b/src/locales/mnw.json
index 09b987756b2..e8b9b6b89c7 100644
--- a/src/locales/mnw.json
+++ b/src/locales/mnw.json
@@ -51,7 +51,7 @@
 	"timeslider.month.october": "\nအံက်တဝ်ပါ",
 	"timeslider.month.november": "\nနဝ်ဝေမ်ပါ",
 	"timeslider.month.december": "ဒဳဇြေန်ပါ",
-	"timeslider.unnamedauthors": "{{num}} ဟွံကဵုယၟု {[ဂမၠိုၚ်(num) မွဲ: ကဝိ, တၞဟ်: ကဝိဂမၠိုၚ် ]}",
+	"timeslider.unnamedauthors": "{{num}} ဟွံကဵုယၟု {[plural(num) one: ကဝိ, other: ကဝိဂမၠိုၚ် ]}",
 	"pad.userlist.entername": "စုတ် ယၟုညးလွပ်",
 	"pad.userlist.unnamed": "ဟွံကဵုလဝ်ယၟု",
 	"pad.impexp.importbutton": " မပၠောပ်စုတ် လၟုဟ်",
diff --git a/src/locales/my.json b/src/locales/my.json
index 522ded52a46..bf5b03c9da5 100644
--- a/src/locales/my.json
+++ b/src/locales/my.json
@@ -149,7 +149,7 @@
 	"timeslider.month.october": "အောက်တိုဘာ",
 	"timeslider.month.november": "နို​ဝင်​ဘာ​",
 	"timeslider.month.december": "ဒီဇင်ဘာ",
-	"timeslider.unnamedauthors": "{{num}} အမည်မဖော်လိုသူ {[အများကိန်း (num) one: author၊ အခြား: author]}",
+	"timeslider.unnamedauthors": "{{num}} အမည်မဖော်လိုသူ {[plural(num) one: author, other: author ]}",
 	"pad.savedrevs.marked": "ယခုပြန်လည်တည်းဖြတ်မှုအားသိမ်းဆည်းထားသောတည်းဖြတ်မှုတစ်ခုအဖြစ်အမှတ်အသားပြုထားသည်",
 	"pad.savedrevs.timeslider": "timeslider ကိုသွားခြင်းဖြင့်သိမ်းဆည်းထားသောပြန်လည်တည်းဖြတ်ချက်များကိုသင်မြင်နိုင်သည်",
 	"pad.userlist.entername": "မင်းနာမည်ထည့်ပါ",
diff --git a/src/locales/ps.json b/src/locales/ps.json
index d48ec2c79e8..b7a91fff569 100644
--- a/src/locales/ps.json
+++ b/src/locales/ps.json
@@ -215,7 +215,7 @@
 	"timeslider.month.october": "اکتوبر",
 	"timeslider.month.november": "نومبر",
 	"timeslider.month.december": "ډېسمبر",
-	"timeslider.unnamedauthors": "{{num}} بې نومه {[ډېرگړي(num) يو: ليکوال، نور: ليکوالان ]}",
+	"timeslider.unnamedauthors": "{{num}} بې نومه {[plural(num) one: ليکوال, other: ليکوالان ]}",
 	"pad.savedrevs.marked": "اوس دا بياليدنه د يوې خوندي شوې بياليدنې په توگه په نښه شوه",
 	"pad.userlist.entername": "نوم مو ورکړئ",
 	"pad.userlist.unnamed": "بې نومه",
diff --git a/src/locales/ro.json b/src/locales/ro.json
index 128187e5dab..79d31cd22d0 100644
--- a/src/locales/ro.json
+++ b/src/locales/ro.json
@@ -126,7 +126,7 @@
 	"timeslider.month.october": "octombrie",
 	"timeslider.month.november": "noiembrie",
 	"timeslider.month.december": "decembrie",
-	"timeslider.unnamedauthors": "{{num}} anonim {[plural (num) unul: autor, altul: autori ]}",
+	"timeslider.unnamedauthors": "{{num}} anonim {[plural(num) one: autor, other: autori ]}",
 	"pad.savedrevs.marked": "Această revizie este marcată acum ca o revizuire salvată",
 	"pad.savedrevs.timeslider": "Puteți vedea reviziile salvate accesând cursorul de timp",
 	"pad.userlist.entername": "Introduceți numele dumneavoastră",
diff --git a/src/locales/sh-latn.json b/src/locales/sh-latn.json
index eb26375efac..ea2bf86197a 100644
--- a/src/locales/sh-latn.json
+++ b/src/locales/sh-latn.json
@@ -121,7 +121,7 @@
 	"timeslider.month.october": "oktobra",
 	"timeslider.month.november": "novembra",
 	"timeslider.month.december": "decembra",
-	"timeslider.unnamedauthors": "{{num}} {[plural(num) one: neimenovani autor, plural(num) two: neimenovana autora, plural(num) other: neimenovanih autora ]}",
+	"timeslider.unnamedauthors": "{{num}} {[plural(num) one: neimenovani autor, two: neimenovana autora, other: neimenovanih autora ]}",
 	"pad.savedrevs.marked": "Ova inačica označena je sada kao spremljena",
 	"pad.savedrevs.timeslider": "Možete pogledati spremljene inačice rabeći vremesledni klizač",
 	"pad.userlist.entername": "Upišite svoje ime",
diff --git a/src/locales/shn.json b/src/locales/shn.json
index dd4d5b84a6e..c957638379a 100644
--- a/src/locales/shn.json
+++ b/src/locales/shn.json
@@ -106,7 +106,7 @@
 	"timeslider.month.october": "ဢွၵ်ႇထူဝ်ႇပႃႇ",
 	"timeslider.month.november": "ၼူဝ်ႇဝႅမ်ႇပႃႇ",
 	"timeslider.month.december": "တီႇသႅမ်ႇပႃႇ",
-	"timeslider.unnamedauthors": "{{num}} ဢမ်ႇသႂ်ႇၸိုဝ်ႈ {[plural(num) ၼိုင်ႈ: ၽူႈတႅမ်ႈလိၵ်ႈ, တၢင်ႇၸိူဝ်း: ၽူႈတႅမ်ႈလိၵ်ႈၶဝ် ]}",
+	"timeslider.unnamedauthors": "{{num}} ဢမ်ႇသႂ်ႇၸိုဝ်ႈ {[plural(num) one: ၽူႈတႅမ်ႈလိၵ်ႈ, other: ၽူႈတႅမ်ႈလိၵ်ႈၶဝ် ]}",
 	"pad.savedrevs.marked": "ဢၼ်မႄးဝႆႉၼႆႉ ယၢမ်းလဵဝ် ၶိုၼ်းမႄး ၵဵပ်းသိမ်းဝႆႉ ၸိူင်ႉၼင်ႇဢၼ်ၼိုင်ႈ",
 	"pad.savedrevs.timeslider": "ၸဝ်ႈၵဝ်ႇတေတူၺ်းလႆႈ ဢၼ်ၶိုၼ်းမႄးသိမ်းဝႆႉၼၼ်ႉယူႇ ပေႃးၶဝ်ႈတူၺ်းတီႈ ၶၢဝ်းယၢမ်းထေႃပူၼ်ႉ",
 	"pad.userlist.entername": "ပေႃႇသႂ်ႇပၼ် ၸိုဝ်ႈၽူႈၸႂ်ႉတိုဝ်း ၸဝ်ႈၵဝ်ႇ",
diff --git a/src/locales/sl.json b/src/locales/sl.json
index 4319253c91b..69bb74ac1da 100644
--- a/src/locales/sl.json
+++ b/src/locales/sl.json
@@ -155,7 +155,7 @@
 	"timeslider.month.october": "oktobra",
 	"timeslider.month.november": "novembra",
 	"timeslider.month.december": "decembra",
-	"timeslider.unnamedauthors": "{{num}} {[plural(num) one: neimenovan avtor, plural(num) two: neimenovana avtorja, plural(num) few: neimenovani avtorji, other: neimenovanih avtorjev ]}",
+	"timeslider.unnamedauthors": "{{num}} {[plural(num) one: neimenovan avtor, two: neimenovana avtorja, few: neimenovani avtorji, other: neimenovanih avtorjev ]}",
 	"pad.savedrevs.marked": "Ta redakcija je zdaj označena kot shranjena redakcija",
 	"pad.savedrevs.timeslider": "Shranjene redakcije si lahko ogledate z odprtjem časovnega traku",
 	"pad.userlist.entername": "Vnesite svoje ime",
diff --git a/src/locales/sq.json b/src/locales/sq.json
index 988c88b3446..1c0f1dad23c 100644
--- a/src/locales/sq.json
+++ b/src/locales/sq.json
@@ -152,7 +152,7 @@
 	"timeslider.month.october": "Tetor",
 	"timeslider.month.november": "Nëntor",
 	"timeslider.month.december": "Dhjetor",
-	"timeslider.unnamedauthors": "{{num}} i paemër {[plural(num) një: autor, tjetër:{{num}} autorë ]}",
+	"timeslider.unnamedauthors": "{{num}} i paemër {[plural(num) one: autor, other: autorë ]}",
 	"pad.savedrevs.marked": "Ky rishikim tani është shënuar si rishikim i ruajtur",
 	"pad.savedrevs.timeslider": "Rishikimet e ruajtura mund t’i shihni duke vizituar rrjedhën kohore",
 	"pad.userlist.entername": "Jepni emrin tuaj",
diff --git a/src/locales/sw.json b/src/locales/sw.json
index 425c28cd1f7..e488cf5e99d 100644
--- a/src/locales/sw.json
+++ b/src/locales/sw.json
@@ -151,7 +151,7 @@
 	"timeslider.month.october": "Oktoba",
 	"timeslider.month.november": "Novemba",
 	"timeslider.month.december": "Desemba",
-	"timeslider.unnamedauthors": "{{num}} haijatajwa jina {[wingi (num) moja: mwandishi, mwingine: waandishi]}",
+	"timeslider.unnamedauthors": "{{num}} haijatajwa jina {[plural(num) one: mwandishi, other: waandishi ]}",
 	"pad.savedrevs.marked": "Marekebisho haya sasa yamewekwa alama kama marekebisho yaliyohifadhiwa",
 	"pad.savedrevs.timeslider": "Unaweza kuona marekebisho yaliyohifadhiwa kwa kutembelea mpangilio wa nyakati",
 	"pad.userlist.entername": "Ingiza jina lako",
diff --git a/src/locales/vi.json b/src/locales/vi.json
index 95f52079c5d..9a517cffe0f 100644
--- a/src/locales/vi.json
+++ b/src/locales/vi.json
@@ -101,7 +101,7 @@
 	"timeslider.month.october": "Tháng Mười",
 	"timeslider.month.november": "Tháng Mười Một",
 	"timeslider.month.december": "Tháng Mười Hai",
-	"timeslider.unnamedauthors": "Không tên {{in a}} {[plural(num) một: tác giả, khác: tác giả]}",
+	"timeslider.unnamedauthors": "Không tên {{in a}} {[plural(num) one: tác giả, other: tác giả ]}",
 	"pad.savedrevs.marked": "Phiên bản này đã được đánh dấu là một phiên bản đã lưu",
 	"pad.userlist.entername": "Nhập tên của bạn",
 	"pad.userlist.unnamed": "Không tên",
diff --git a/src/tests/backend-new/specs/locale-files.test.ts b/src/tests/backend-new/specs/locale-files.test.ts
new file mode 100644
index 00000000000..6cf0d73635a
--- /dev/null
+++ b/src/tests/backend-new/specs/locale-files.test.ts
@@ -0,0 +1,101 @@
+'use strict';
+
+import {readFileSync, readdirSync} from 'fs';
+import {join} from 'path';
+import {describe, it, expect} from 'vitest';
+
+const repoRoot = join(__dirname, '..', '..', '..', '..');
+const localesDir = join(repoRoot, 'src', 'locales');
+const localeFiles = readdirSync(localesDir)
+    .filter((f) => f.endsWith('.json'))
+    .map((f) => join(localesDir, f));
+
+const macroCandidateRe = /\{\[[^]*?]}/g;
+
+const parseMacro = (candidate: string): {macroName: string, options: string} | null => {
+  if (!candidate.startsWith('{[') || !candidate.endsWith(']}')) return null;
+  const body = candidate.slice(2, -2).trim();
+  const openParen = body.indexOf('(');
+  const closeParen = body.indexOf(')', openParen + 1);
+  if (openParen <= 0 || closeParen <= openParen + 1) return null;
+  const macroName = body.slice(0, openParen).trim();
+  const variableName = body.slice(openParen + 1, closeParen).trim();
+  if (!/^[a-zA-Z]+$/.test(macroName) || !/^[a-zA-Z]+$/.test(variableName)) return null;
+  return {macroName, options: body.slice(closeParen + 1).trim()};
+};
+
+const parsePluralOptionNames = (options: string): string[] | null => {
+  if (options === '') return [];
+  const names: string[] = [];
+  let i = 0;
+  while (i < options.length) {
+    while (i < options.length && /\s/.test(options[i])) i++;
+    const nameStart = i;
+    while (i < options.length && /[a-zA-Z]/.test(options[i])) i++;
+    if (nameStart === i || options[i] !== ':') return null;
+    names.push(options.slice(nameStart, i));
+    i++;
+    while (i < options.length) {
+      if (options[i] === ',') {
+        i++;
+        break;
+      }
+      i++;
+    }
+  }
+  return names;
+};
+const allowedMacros = new Set(['plural']);
+const allowedPluralOptions = new Set(['zero', 'one', 'two', 'few', 'many', 'other']);
+
+describe('locale files', () => {
+  it('current locale corpus contains no unsupported macros', () => {
+    const failures: string[] = [];
+    for (const file of localeFiles) {
+      const rel = file.replace(repoRoot + '/', '');
+      const parsed = JSON.parse(readFileSync(file, 'utf8')) as Record<string, string>;
+      for (const [key, value] of Object.entries(parsed)) {
+        if (key === '@metadata') continue;
+        for (const candidate of value.match(macroCandidateRe) ?? []) {
+          const macro = parseMacro(candidate);
+          if (macro == null) {
+            failures.push(`${rel}:${key}:malformed:${candidate}`);
+            continue;
+          }
+          const {macroName, options} = macro;
+          if (!allowedMacros.has(macroName)) failures.push(`${rel}:${key}:${macroName}`);
+          if (macroName !== 'plural') continue;
+          const optionNames = parsePluralOptionNames(options);
+          if (optionNames == null) {
+            failures.push(`${rel}:${key}:malformed:${candidate}`);
+            continue;
+          }
+          for (const name of optionNames) {
+            if (!allowedPluralOptions.has(name)) failures.push(`${rel}:${key}:${name}`);
+          }
+        }
+      }
+    }
+    expect(failures).toEqual([]);
+  });
+
+  for (const file of localeFiles) {
+    const rel = file.replace(repoRoot + '/', '');
+
+    it(`${rel} contains a JSON object of string translations`, () => {
+      const parsed = JSON.parse(readFileSync(file, 'utf8'));
+      expect(parsed, `${rel} must contain a JSON object`).toBeTruthy();
+      expect(Array.isArray(parsed), `${rel} must not contain a JSON array`).toBe(false);
+      expect(typeof parsed, `${rel} must contain a JSON object`).toBe('object');
+      for (const [key, value] of Object.entries(parsed as Record<string, unknown>)) {
+        if (key === '@metadata') {
+          expect(value != null && typeof value === 'object' && !Array.isArray(value),
+            `${rel} key @metadata must map to an object`).toBe(true);
+          continue;
+        }
+        expect(typeof value, `${rel} key ${key} must map to a string`).toBe('string');
+      }
+    });
+
+  }
+});