diff --git a/README.md b/README.md
index d34e3ce..2c9e291 100644
--- a/README.md
+++ b/README.md
@@ -28,7 +28,7 @@ Validate is a standard Deno module for validating string.
 * [x] isFloat
 * [x] isFQDN
 * [x] isFullWidth
-* [ ] isHalfWidth
+* [x] isHalfWidth
 * [ ] isHash
 * [ ] isHexColor
 * [ ] isHexadecimal
diff --git a/src/libs/isHalfWidth.ts b/src/libs/isHalfWidth.ts
new file mode 100644
index 0000000..d101f81
--- /dev/null
+++ b/src/libs/isHalfWidth.ts
@@ -0,0 +1,9 @@
+// @ts-ignore allowing typedoc to build
+import assertString from '../utils/assertString.ts';
+
+export const halfWidth = /[\u0020-\u007E\uFF61-\uFF9F\uFFA0-\uFFDC\uFFE8-\uFFEE0-9a-zA-Z]/;
+
+export const isHalfWidth = (str: string) => {
+  assertString(str);
+  return halfWidth.test(str);
+};
diff --git a/src/mod.ts b/src/mod.ts
index ebc3d64..189eb27 100644
--- a/src/mod.ts
+++ b/src/mod.ts
@@ -42,3 +42,5 @@ export * from './libs/isFloat.ts';
 export * from './libs/isFQDN.ts';
 // @ts-ignore allowing typedoc to build
 export * from './libs/isFullWidth.ts';
+// @ts-ignore allowing typedoc to build
+export * from './libs/isHalfWidth.ts';