diff --git a/README.md b/README.md
index 6c4058a..464509b 100644
--- a/README.md
+++ b/README.md
@@ -7,4 +7,26 @@ React translation library built with the Bun 🐰 runtime and Cursor AI 🖱️
 - Built for client-side Serverless architectures on the web
 - Supports React Native
 - `<Text id="myTranslationKey" />` component to render translations
-- Replacements in translations: {}
+- Replacements with `{}` in translations
+
+## Usage
+
+```ts
+import { translations } from 'epic-language'
+
+const { translate } = translations(
+  // Initial translations in default language.
+  {
+    title: 'My Title',
+    description: 'This is the description.',
+    counter: 'Count: {}',
+  },
+  // Route to load translations for user language.
+  '/api/translations',
+  // Callback for when translations have been loaded.
+  onLoad,
+)
+
+translate('title') // My Title
+translate('counter', '5') // Counter: 5
+```
diff --git a/index.ts b/index.ts
index dc10c80..b5cde06 100644
--- a/index.ts
+++ b/index.ts
@@ -3,6 +3,7 @@ import { log } from './helper'
 
 type Sheet = { [key: string]: string }
 type Sheets = { [key in Language]?: Sheet }
+type Replacement = string | number
 
 const sheets: Sheets = {}
 
@@ -40,25 +41,44 @@ async function loadSheet(apiRoute: string, onLoad: () => void, defaultLanguage:
   })
 }
 
+function insertReplacements(translation: string, replacements?: Replacement | Replacement[]) {
+  if (!replacements) return translation
+
+  if (!Array.isArray(replacements)) {
+    // eslint-disable-next-line no-param-reassign
+    replacements = [replacements]
+  }
+
+  let result = translation
+  for (let index = 0; index < replacements.length; index += 1) {
+    result = result.replace('{}', String(replacements[index]))
+  }
+  return result
+}
+
 // defaultLanguage is the language in the standard translation that's always loaded.
 export function translations<T extends Sheet>(
   defaultTranslations: T,
   apiRoute: string,
-  onLoad: () => void,
+  onLoad: () => void = () => {},
   defaultLanguage: Language = Language.en,
 ) {
   sheets[defaultLanguage] = defaultTranslations
 
   loadSheet(apiRoute, onLoad, defaultLanguage)
 
-  function translate(key: keyof T, language: Language = defaultLanguage) {
+  function translate(
+    key: keyof T,
+    replacements?: Replacement | Replacement[],
+    language: Language = defaultLanguage,
+  ) {
     const sheet = sheets[language]
     if (!has(sheet, key)) {
       log(`Translation for key "${String(key)}" is missing`)
       if (Object.hasOwn(sheets[defaultLanguage], key)) return sheets[defaultLanguage][key as string]
       return key
     }
-    return sheet[key as string]
+    return insertReplacements(sheet[key as string], replacements)
   }
 
   return { translate }
diff --git a/test/basic.test.tsx b/test/basic.test.tsx
index 07383fb..0717b0a 100644
--- a/test/basic.test.tsx
+++ b/test/basic.test.tsx
@@ -1,3 +1,5 @@
+/// <reference lib="dom" />
+
 import React from 'react'
 import { test, expect, mock, spyOn } from 'bun:test'
 import { render } from '@testing-library/react'
@@ -9,6 +11,7 @@ GlobalRegistrator.register()
 console.log = log // Restore log to show up in tests during development.
 
 const windowLanguageSpy = spyOn(window, 'navigator')
+// @ts-ignore
 windowLanguageSpy.mockImplementation(() => ({ language: 'en_US' }))
 
 test('Can render a basic app.', async () => {
@@ -32,7 +35,7 @@ test('Can render a basic app.', async () => {
 })
 
 test('Translates key in initially provided language.', () => {
-  const onLoad = mock()
+  const onLoad = mock(() => {})
   const { translate } = translations(
     { title: 'My Title', description: 'This is the description.' },
     '/api/translations',
@@ -49,7 +52,7 @@ test('Translates key in initially provided language.', () => {
 
 test('Symbols or numbers cannot be used as keys.', () => {
   // TODO doesn't seem possible to restrict keys to string when using generic type with extends.
-  const onLoad = mock()
+  const onLoad = mock(() => {})
   const symbol = Symbol('test')
   const { translate } = translations(
     { [symbol]: 'My Symbol', 5: 'My Number' },
@@ -64,3 +67,10 @@ test('Symbols or numbers cannot be used as keys.', () => {
   expect(translate('missing')).toBe('missing')
   expect(onLoad).toHaveBeenCalled()
 })
+
+test('Replacements are inserted.', () => {
+  const { translate } = translations({ counter: 'Count: {}' }, '/api/translations')
+
+  expect(translate('counter', '123')).toBe('Count: 123')
+  expect(translate('counter', 456)).toBe('Count: 456')
+})