diff --git a/__tests__/Auth0Client/getTokenSilently.test.ts b/__tests__/Auth0Client/getTokenSilently.test.ts
index 17b017f0a..2c46b1cbc 100644
--- a/__tests__/Auth0Client/getTokenSilently.test.ts
+++ b/__tests__/Auth0Client/getTokenSilently.test.ts
@@ -1685,7 +1685,7 @@ describe('Auth0Client', () => {
           redirect_uri: TEST_REDIRECT_URI,
           client_id: TEST_CLIENT_ID,
           grant_type: 'authorization_code',
-          custom_param: 'hello+world',
+          custom_param: 'hello world',
           another_custom_param: 'bar',
           code_verifier: TEST_CODE_VERIFIER
         },
diff --git a/__tests__/Auth0Client/helpers.ts b/__tests__/Auth0Client/helpers.ts
index 794282c4b..6d94f0d82 100644
--- a/__tests__/Auth0Client/helpers.ts
+++ b/__tests__/Auth0Client/helpers.ts
@@ -42,7 +42,12 @@ export const assertPostFn = (mockFetch: jest.Mock) => {
     expect(url).toEqual(actualUrl);
 
     expect(body).toEqual(
-      json ? JSON.parse(call.body) : utils.parseQueryResult(call.body)
+      json
+        ? JSON.parse(call.body)
+        : Array.from(new URLSearchParams(call.body).entries()).reduce(
+            (acc, curr) => ({ ...acc, [curr[0]]: curr[1] }),
+            {}
+          )
     );
 
     if (headers) {
diff --git a/__tests__/index.test.ts b/__tests__/index.test.ts
index 37a5dae4e..29f43b5d3 100644
--- a/__tests__/index.test.ts
+++ b/__tests__/index.test.ts
@@ -50,7 +50,7 @@ const setup = async (
   utils.sha256.mockReturnValue(Promise.resolve(TEST_ARRAY_BUFFER));
   utils.bufferToBase64UrlEncoded.mockReturnValue(TEST_BASE64_ENCODED_STRING);
 
-  utils.parseQueryResult.mockReturnValue({
+  utils.parseAuthenticationResult.mockReturnValue({
     state: TEST_ENCODED_STATE,
     code: TEST_CODE
   });
diff --git a/__tests__/utils.test.ts b/__tests__/utils.test.ts
index 1ef521977..5c8cef4e7 100644
--- a/__tests__/utils.test.ts
+++ b/__tests__/utils.test.ts
@@ -1,5 +1,5 @@
 import {
-  parseQueryResult,
+  parseAuthenticationResult,
   createQueryParams,
   bufferToBase64UrlEncoded,
   createRandomString,
@@ -23,29 +23,42 @@ afterEach(() => {
 });
 
 describe('utils', () => {
-  describe('parseQueryResult', () => {
+  describe('parseAuthenticationResult', () => {
     it('parses the query string', () => {
       expect(
-        parseQueryResult('value=test&otherValue=another-test')
+        parseAuthenticationResult('code=test&state=another-test')
       ).toMatchObject({
-        value: 'test',
-        otherValue: 'another-test'
+        code: 'test',
+        state: 'another-test'
       });
     });
+
+    it('parses the query string when containing raw =', () => {
+      expect(
+        parseAuthenticationResult('code=test&state=another-test==')
+      ).toMatchObject({
+        code: 'test',
+        state: 'another-test=='
+      });
+    });
+
+    it('parses the query string when containing url encoded =', () => {
+      expect(
+        parseAuthenticationResult('code=test&state=another-test%3D%3D')
+      ).toMatchObject({
+        code: 'test',
+        state: 'another-test=='
+      });
+    });
+
     it('strips off hash values', () => {
       expect(
-        parseQueryResult('code=some-code&state=some-state#__')
+        parseAuthenticationResult('code=some-code&state=some-state#__')
       ).toMatchObject({
         code: 'some-code',
         state: 'some-state'
       });
     });
-    it('converts `expires_in` to int', () => {
-      expect(parseQueryResult('value=test&expires_in=10')).toMatchObject({
-        value: 'test',
-        expires_in: 10
-      });
-    });
   });
   describe('createQueryParams', () => {
     it('creates query string from object', () => {
diff --git a/src/Auth0Client.ts b/src/Auth0Client.ts
index 7389fc7a3..41d21ea35 100644
--- a/src/Auth0Client.ts
+++ b/src/Auth0Client.ts
@@ -3,7 +3,7 @@ import Lock from 'browser-tabs-lock';
 import {
   createQueryParams,
   runPopup,
-  parseQueryResult,
+  parseAuthenticationResult,
   encode,
   createRandomString,
   runIframe,
@@ -486,7 +486,7 @@ export class Auth0Client {
       throw new Error('There are no query params available for parsing.');
     }
 
-    const { state, code, error, error_description } = parseQueryResult(
+    const { state, code, error, error_description } = parseAuthenticationResult(
       queryStringFragments.join('')
     );
 
diff --git a/src/utils.ts b/src/utils.ts
index b1dbf5836..1c055f002 100644
--- a/src/utils.ts
+++ b/src/utils.ts
@@ -12,24 +12,21 @@ import {
   PopupCancelledError
 } from './errors';
 
-export const parseQueryResult = (queryString: string): AuthenticationResult => {
+export const parseAuthenticationResult = (
+  queryString: string
+): AuthenticationResult => {
   if (queryString.indexOf('#') > -1) {
-    queryString = queryString.substr(0, queryString.indexOf('#'));
+    queryString = queryString.substring(0, queryString.indexOf('#'));
   }
 
-  const queryParams = queryString.split('&');
-  const parsedQuery: Record<string, any> = {};
+  const searchParams = new URLSearchParams(queryString);
 
-  queryParams.forEach(qp => {
-    const [key, val] = qp.split('=');
-    parsedQuery[key] = decodeURIComponent(val);
-  });
-
-  if (parsedQuery.expires_in) {
-    parsedQuery.expires_in = parseInt(parsedQuery.expires_in);
-  }
-
-  return parsedQuery as AuthenticationResult;
+  return {
+    state: searchParams.get('state')!,
+    code: searchParams.get('code') || undefined,
+    error: searchParams.get('error') || undefined,
+    error_description: searchParams.get('error_description') || undefined
+  };
 };
 
 export const runIframe = (