diff --git a/package.json b/package.json
index e2de296..d5de04c 100644
--- a/package.json
+++ b/package.json
@@ -23,6 +23,7 @@
     "pnpm": ">=9.1.0"
   },
   "devDependencies": {
+    "@type-challenges/utils": "0.1.1",
     "@types/node": "20.12.11",
     "eslint": "9.2.0",
     "typescript": "5.4.5",
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 4c5b769..b482386 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -8,6 +8,9 @@ importers:
 
   .:
     devDependencies:
+      '@type-challenges/utils':
+        specifier: 0.1.1
+        version: 0.1.1
       '@types/node':
         specifier: 20.12.11
         version: 20.12.11
@@ -285,6 +288,9 @@ packages:
   '@sinclair/typebox@0.27.8':
     resolution: {integrity: sha512-+Fj43pSMwJs4KRrH/938Uf+uAELIgVBmQzg/q1YG10djyfA3TnrU8N8XzqCh/okZdszqBQTZf96idMfE5lnwTA==}
 
+  '@type-challenges/utils@0.1.1':
+    resolution: {integrity: sha512-A7ljYfBM+FLw+NDyuYvGBJiCEV9c0lPWEAdzfOAkb3JFqfLl0Iv/WhWMMARHiRKlmmiD1g8gz/507yVvHdQUYA==}
+
   '@types/estree@1.0.5':
     resolution: {integrity: sha512-/kYRxGDLWzHOB7q+wtSUQlFrtcdUccpfy+X+9iMBpHK8QLLhx2wIPYuS5DYtR9Wa/YlZAbIovy7qVdB1Aq6Lyw==}
 
@@ -1182,6 +1188,8 @@ snapshots:
 
   '@sinclair/typebox@0.27.8': {}
 
+  '@type-challenges/utils@0.1.1': {}
+
   '@types/estree@1.0.5': {}
 
   '@types/json-schema@7.0.15': {}
diff --git a/types/Branded.test.ts b/types/Branded.test.ts
new file mode 100644
index 0000000..262051a
--- /dev/null
+++ b/types/Branded.test.ts
@@ -0,0 +1,57 @@
+import type { Equal, Expect, NotEqual } from '@type-challenges/utils'
+import { expect, test } from 'vitest'
+import { raise } from '../raise/index.js'
+import { Branded } from './Branded.ts'
+
+/** branded numbers */
+type Age = Branded<number, 'Age'>
+type Year = Branded<number, 'Year'>
+
+const validAge = (age: number): Age | undefined =>
+  age >= 0 && age <= 125 ? age as Age : undefined
+
+const birthYear = (age: Age, now: Date): Year =>
+  now.getFullYear() - age as Year // it's incorrect, but sufficient for demo purpose
+
+test('birthYear is compile-time safe', () => {
+  const fiveYears = validAge(5) ?? raise('invalid age')
+  expect(
+    birthYear(fiveYears, new Date(2024, 4, 11))
+  ).toBe(2019)
+})
+
+test('birthYear is compile-time safe', () => {
+  expect(
+    // @ts-expect-error argument must be Age
+    birthYear(5, new Date(2024, 4, 11))
+  ).toBe(2019)
+})
+
+const someAge = validAge(5) ?? raise('invalid age')
+const someBirthYear = birthYear(someAge, new Date(2024, 4, 11))
+
+// @ts-ignore unused
+type AgeTests = [
+  Expect<Equal<typeof someAge, Age>>,
+  Expect<NotEqual<typeof someAge, number>>,
+  Expect<Equal<Parameters<typeof validAge>, [number]>>,
+  Expect<Equal<Parameters<typeof birthYear>, [Age, Date]>>,
+  Expect<Equal<typeof someBirthYear, Year>>,
+  Expect<NotEqual<typeof someBirthYear, number>>,
+]
+
+/** branded string */
+type Email = Branded<string, 'Email'>
+
+const emailRegex = /^(([^<>()\[\]\\.,;:\s@"]+(\.[^<>()\[\]\\.,;:\s@"]+)*)|(".+"))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$/
+const validEmail = (email: string): Email | undefined =>
+  emailRegex.test(email) ? email as Email : undefined
+
+const someEmail = validEmail('abc@mail.com') ?? raise('invalid email')
+
+// @ts-ignore unused
+type EmailTests = [
+  Expect<Equal<typeof someEmail, Email>>,
+  Expect<NotEqual<typeof someEmail, string>>,
+  Expect<Equal<Parameters<typeof validEmail>, [string]>>,
+]
diff --git a/types/Branded.ts b/types/Branded.ts
new file mode 100644
index 0000000..c992e14
--- /dev/null
+++ b/types/Branded.ts
@@ -0,0 +1,3 @@
+declare const __brand: unique symbol
+type Brand<B> = { [__brand]: B }
+export type Branded<T, B> = T & Brand<B>
diff --git a/types/index.ts b/types/index.ts
index cd80594..efe43e2 100644
--- a/types/index.ts
+++ b/types/index.ts
@@ -1 +1,2 @@
+export * from './Branded.ts'
 export * from './DeepPartial.ts'