diff --git a/packages/docusaurus-plugin-content-blog/src/client/sidebarUtils.tsx b/packages/docusaurus-plugin-content-blog/src/client/sidebarUtils.tsx
index 88d3a41f3f2c..b9431d100d3d 100644
--- a/packages/docusaurus-plugin-content-blog/src/client/sidebarUtils.tsx
+++ b/packages/docusaurus-plugin-content-blog/src/client/sidebarUtils.tsx
@@ -8,7 +8,6 @@
 import {type ReactNode, useMemo} from 'react';
 import {useLocation} from '@docusaurus/router';
 import Link from '@docusaurus/Link';
-import {groupBy} from '@docusaurus/theme-common';
 import {isSamePath} from '@docusaurus/theme-common/internal';
 import type {BlogSidebarItem} from '@docusaurus/plugin-content-blog';
 
@@ -36,7 +35,7 @@ export function useVisibleBlogSidebarItems(
 export function groupBlogSidebarItemsByYear(
   items: BlogSidebarItem[],
 ): [string, BlogSidebarItem[]][] {
-  const groupedByYear = groupBy(items, (item) => {
+  const groupedByYear = Object.groupBy(items, (item) => {
     return `${new Date(item.date).getFullYear()}`;
   });
   // "as" is safe here
diff --git a/packages/docusaurus-theme-common/src/index.ts b/packages/docusaurus-theme-common/src/index.ts
index 5a49c06daaad..23229a1b645b 100644
--- a/packages/docusaurus-theme-common/src/index.ts
+++ b/packages/docusaurus-theme-common/src/index.ts
@@ -77,7 +77,7 @@ export {isMultiColumnFooterLinks} from './utils/footerUtils';
 
 export {isRegexpStringMatch} from './utils/regexpUtils';
 
-export {duplicates, uniq, groupBy} from './utils/jsUtils';
+export {duplicates, uniq} from './utils/jsUtils';
 
 export {usePrismTheme} from './hooks/usePrismTheme';
 
diff --git a/packages/docusaurus-theme-common/src/utils/__tests__/jsUtils.test.ts b/packages/docusaurus-theme-common/src/utils/__tests__/jsUtils.test.ts
index 7f14acc1a878..f494e33d0ece 100644
--- a/packages/docusaurus-theme-common/src/utils/__tests__/jsUtils.test.ts
+++ b/packages/docusaurus-theme-common/src/utils/__tests__/jsUtils.test.ts
@@ -6,7 +6,7 @@
  */
 
 import {describe, expect, it} from 'vitest';
-import {uniq, duplicates, groupBy} from '../jsUtils';
+import {uniq, duplicates} from '../jsUtils';
 
 describe('duplicates', () => {
   it('gets duplicate values', () => {
@@ -52,55 +52,3 @@ describe('uniq', () => {
     ).toEqual([obj1, obj2, array1, array3, array2, obj3]);
   });
 });
-
-describe('groupBy', () => {
-  type User = {name: string; age: number; type: 'a' | 'b' | 'c'};
-
-  const user1: User = {name: 'Seb', age: 42, type: 'c'};
-  const user2: User = {name: 'Robert', age: 42, type: 'b'};
-  const user3: User = {name: 'Seb', age: 32, type: 'c'};
-
-  const users = [user1, user2, user3];
-
-  it('group by name', () => {
-    const groups = groupBy(users, (u) => u.name);
-
-    expect(Object.keys(groups)).toEqual(['Seb', 'Robert']);
-    expect(groups).toEqual({
-      Seb: [user1, user3],
-      Robert: [user2],
-    });
-  });
-
-  it('group by age', () => {
-    const groups = groupBy(users, (u) => u.age);
-
-    // Surprising keys order due to JS behavior
-    // see https://x.com/sebastienlorber/status/1806371668614369486
-    expect(Object.keys(groups)).toEqual(['32', '42']);
-    expect(groups).toEqual({
-      '32': [user3],
-      '42': [user1, user2],
-    });
-  });
-
-  it('group by type', () => {
-    const groups = groupBy(users, (u) => u.type);
-
-    expect(Object.keys(groups)).toEqual(['c', 'b']);
-    expect(groups).toEqual({
-      c: [user1, user3],
-      b: [user2],
-    });
-  });
-
-  it('group by name even duplicates', () => {
-    const groups = groupBy([user1, user2, user3, user1, user3], (u) => u.name);
-
-    expect(Object.keys(groups)).toEqual(['Seb', 'Robert']);
-    expect(groups).toEqual({
-      Seb: [user1, user3, user1, user3],
-      Robert: [user2],
-    });
-  });
-});
diff --git a/packages/docusaurus-theme-common/src/utils/jsUtils.ts b/packages/docusaurus-theme-common/src/utils/jsUtils.ts
index f1f0ac92010d..740a5a8b61df 100644
--- a/packages/docusaurus-theme-common/src/utils/jsUtils.ts
+++ b/packages/docusaurus-theme-common/src/utils/jsUtils.ts
@@ -34,21 +34,3 @@ export function uniq<T>(arr: T[]): T[] {
   // Note: had problems with [...new Set()]: https://github.com/facebook/docusaurus/issues/4972#issuecomment-863895061
   return Array.from(new Set(arr));
 }
-
-// TODO 2025: replace by std Object.groupBy ?
-// This is a local polyfill with exact same TS signature
-// see https://github.com/microsoft/TypeScript/blob/main/src/lib/esnext.object.d.ts
-export function groupBy<K extends PropertyKey, T>(
-  items: Iterable<T>,
-  keySelector: (item: T, index: number) => K,
-): Partial<Record<K, T[]>> {
-  const result: Partial<Record<K, T[]>> = {};
-  let index = 0;
-  for (const item of items) {
-    const key = keySelector(item, index);
-    result[key] ??= [];
-    result[key]!.push(item);
-    index += 1;
-  }
-  return result;
-}