diff --git a/packages/sdk/react-native/__tests__/platform/PlatformEncoding.test.ts b/packages/sdk/react-native/__tests__/platform/PlatformEncoding.test.ts
new file mode 100644
index 0000000000..1b3ed3f807
--- /dev/null
+++ b/packages/sdk/react-native/__tests__/platform/PlatformEncoding.test.ts
@@ -0,0 +1,13 @@
+import PlatformEncoding from '../../src/platform/PlatformEncoding';
+
+it('can base64 a basic ASCII string', () => {
+  const encoding = new PlatformEncoding();
+  expect(encoding.btoa('toaster')).toEqual('dG9hc3Rlcg==');
+});
+
+it('can base64 a unicode string containing multi-byte character', () => {
+  const encoding = new PlatformEncoding();
+  expect(encoding.btoa('✇⽊❽⾵⊚▴ⶊ↺➹≈⋟⚥⤅⊈ⲏⷨ⾭Ⲗ⑲▯ⶋₐℛ⬎⿌🦄')).toEqual(
+    '4pyH4r2K4p294r614oqa4pa04raK4oa64p654omI4ouf4pql4qSF4oqI4rKP4reo4r6t4rKW4pGy4pav4raL4oKQ4oSb4qyO4r+M8J+mhA==',
+  );
+});
diff --git a/packages/sdk/react-native/src/polyfills/btoa.ts b/packages/sdk/react-native/src/polyfills/btoa.ts
index d9b29bfac0..4b59523884 100644
--- a/packages/sdk/react-native/src/polyfills/btoa.ts
+++ b/packages/sdk/react-native/src/polyfills/btoa.ts
@@ -1,15 +1,10 @@
+/* eslint-disable no-bitwise */
 import { fromByteArray } from 'base64-js';
 
-function convertToByteArray(s: string) {
-  const b = [];
-  for (let i = 0; i < s.length; i += 1) {
-    b.push(s.charCodeAt(i));
-  }
-  return Uint8Array.from(b);
-}
+import toUtf8Array from './toUtf8Array';
 
 export function btoa(s: string) {
-  return fromByteArray(convertToByteArray(s));
+  return fromByteArray(toUtf8Array(s));
 }
 
 export function base64FromByteArray(a: Uint8Array) {
diff --git a/packages/sdk/react-native/src/polyfills/toUtf8Array.ts b/packages/sdk/react-native/src/polyfills/toUtf8Array.ts
new file mode 100644
index 0000000000..e582754356
--- /dev/null
+++ b/packages/sdk/react-native/src/polyfills/toUtf8Array.ts
@@ -0,0 +1,50 @@
+/* eslint-disable no-plusplus */
+/* eslint-disable no-bitwise */
+
+// Originally from: https://github.com/google/closure-library/blob/a1f5a029c1b32eb4793a2d920aa52abc085e1bf7/closure/goog/crypt/crypt.js
+
+// Once React Native versions uniformly support TextEncoder this code can be removed.
+
+// Copyright 2008 The Closure Library Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS-IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+export default function toUtf8Array(str: string): Uint8Array {
+  const out: number[] = [];
+  let p = 0;
+  for (let i = 0; i < str.length; i += 1) {
+    let c = str.charCodeAt(i);
+    if (c < 128) {
+      out[p++] = c;
+    } else if (c < 2048) {
+      out[p++] = (c >> 6) | 192;
+      out[p++] = (c & 63) | 128;
+    } else if (
+      (c & 0xfc00) === 0xd800 &&
+      i + 1 < str.length &&
+      (str.charCodeAt(i + 1) & 0xfc00) === 0xdc00
+    ) {
+      // Surrogate Pair
+      c = 0x10000 + ((c & 0x03ff) << 10) + (str.charCodeAt(++i) & 0x03ff);
+      out[p++] = (c >> 18) | 240;
+      out[p++] = ((c >> 12) & 63) | 128;
+      out[p++] = ((c >> 6) & 63) | 128;
+      out[p++] = (c & 63) | 128;
+    } else {
+      out[p++] = (c >> 12) | 224;
+      out[p++] = ((c >> 6) & 63) | 128;
+      out[p++] = (c & 63) | 128;
+    }
+  }
+  return Uint8Array.from(out);
+}