diff --git a/src/build/base64-impl-browser.spec.ts b/src/build/base64-impl-browser.spec.ts
index 6078d0c3b..ddd2f9a75 100644
--- a/src/build/base64-impl-browser.spec.ts
+++ b/src/build/base64-impl-browser.spec.ts
@@ -52,6 +52,11 @@ describe('base64-impl/browser', function () {
     it('should encode boolean strings', function () {
       expect(base64.base64Encode('true')).toBe('dHJ1ZQ==')
     })
+
+    it('should encode a large string', function () {
+      const str = 'Hello 🌍'.repeat(20000)
+      expect(base64.base64Encode(str)).toBe(Buffer.from(str).toString('base64'))
+    })
   })
 
   describe('#base64Decode()', function () {
diff --git a/src/build/base64-impl-browser.ts b/src/build/base64-impl-browser.ts
index 100cf9f21..48ce759c7 100644
--- a/src/build/base64-impl-browser.ts
+++ b/src/build/base64-impl-browser.ts
@@ -1,6 +1,11 @@
 
 export function base64Encode (str: string): string {
-  return btoa(String.fromCharCode(...new TextEncoder().encode(str)))
+  const bytes = new TextEncoder().encode(str)
+  let binary = ''
+  for (let i = 0; i < bytes.length; i += 0x8000) {
+    binary += String.fromCharCode(...bytes.subarray(i, i + 0x8000))
+  }
+  return btoa(binary)
 }
 
 export function base64Decode (str: string): string {