diff --git a/packages/util/src/is/ascii.spec.ts b/packages/util/src/is/ascii.spec.ts
index 303cd85b9..95a4b25b8 100644
--- a/packages/util/src/is/ascii.spec.ts
+++ b/packages/util/src/is/ascii.spec.ts
@@ -1,6 +1,7 @@
 // Copyright 2017-2022 @polkadot/util authors & contributors
 // SPDX-License-Identifier: Apache-2.0
 
+import { performance } from '../test/performance';
 import { isAscii } from '.';
 
 describe('isAscii', (): void => {
@@ -35,4 +36,6 @@ describe('isAscii', (): void => {
   it('returns false for hex input, non-ascii', (): void => {
     expect(isAscii('0x010203')).toEqual(false);
   });
+
+  performance('isAscii', 100_000, [[[0x31, 0x32, 0x20, 10, 9, 13, 65, 66, 67, 68, 69, 70]]], isAscii);
 });
diff --git a/packages/util/src/is/ascii.ts b/packages/util/src/is/ascii.ts
index ee65541e3..9c79e18e8 100644
--- a/packages/util/src/is/ascii.ts
+++ b/packages/util/src/is/ascii.ts
@@ -1,25 +1,42 @@
 // Copyright 2017-2022 @polkadot/util authors & contributors
 // SPDX-License-Identifier: Apache-2.0
 
-import type { U8aLike } from '../types';
+import type { AnyString, U8aLike } from '../types';
 
 import { u8aToU8a } from '../u8a/toU8a';
 import { isHex } from './hex';
 import { isString } from './string';
 
-const FORMAT = [9, 10, 13];
-
 /** @internal */
-function isAsciiByte (b: number): boolean {
-  return (b < 127) && (
-    (b >= 32) ||
-    FORMAT.includes(b)
-  );
+function isAsciiStr (str: AnyString): boolean {
+  const count = str.length;
+
+  for (let i = 0; i < count; i++) {
+    const b = str.charCodeAt(i);
+
+    // check is inlined here, it is faster than making a call
+    if (!((b < 127) && ((b >= 32) || (b === 10) || (b === 9) || (b === 13)))) {
+      return false;
+    }
+  }
+
+  return true;
 }
 
 /** @internal */
-function isAsciiChar (s: string): boolean {
-  return isAsciiByte(s.charCodeAt(0));
+function isAsciiU8a (u8a: Uint8Array): boolean {
+  const count = u8a.length;
+
+  for (let i = 0; i < count; i++) {
+    const b = u8a[i];
+
+    // check is inlined here, it is faster than making a call
+    if (!((b < 127) && ((b >= 32) || (b === 10) || (b === 9) || (b === 13)))) {
+      return false;
+    }
+  }
+
+  return true;
 }
 
 /**
@@ -29,13 +46,9 @@ function isAsciiChar (s: string): boolean {
  * Checks to see if the input string or Uint8Array is printable ASCII, 32-127 + formatters
  */
 export function isAscii (value?: U8aLike | null): boolean {
-  const isStringIn = isString(value);
-
-  if (value) {
-    return isStringIn && !isHex(value)
-      ? value.toString().split('').every(isAsciiChar)
-      : u8aToU8a(value).every(isAsciiByte);
-  }
-
-  return isStringIn;
+  return isString(value) && !isHex(value)
+    ? isAsciiStr(value)
+    : value
+      ? isAsciiU8a(u8aToU8a(value))
+      : false;
 }
diff --git a/packages/util/src/u8a/toString.spec.ts b/packages/util/src/u8a/toString.spec.ts
index 9370ec093..626b39dd2 100644
--- a/packages/util/src/u8a/toString.spec.ts
+++ b/packages/util/src/u8a/toString.spec.ts
@@ -1,7 +1,7 @@
 // Copyright 2017-2022 @polkadot/util authors & contributors
 // SPDX-License-Identifier: Apache-2.0
 
-import { u8aToString } from '..';
+import { u8aToString } from '.';
 
 describe('u8aToString', (): void => {
   it('decodes to an empty string for undefined', (): void => {
@@ -16,11 +16,19 @@ describe('u8aToString', (): void => {
     ).toEqual('');
   });
 
-  it('decodes the buffer correctly', (): void => {
+  it('decodes the Uint8Array correctly', (): void => {
     expect(
       u8aToString(
         new Uint8Array([208, 159, 209, 128, 208, 184, 208, 178, 208, 181, 209, 130, 44, 32, 208, 188, 208, 184, 209, 128, 33])
       )
     ).toEqual('Привет, мир!');
   });
+
+  it('decodes the Uint8Array correctly', (): void => {
+    expect(
+      u8aToString(
+        new Uint8Array([0x68, 0x65, 0x6c, 0x6c, 0x6f, 0x20, 0x77, 0x6f, 0x72, 0x6c, 0x64])
+      )
+    ).toEqual('hello world');
+  });
 });