diff --git a/admin_sdk/directory/quickstart.py b/admin_sdk/directory/quickstart.py
index 5a9b0680..caf0d994 100644
--- a/admin_sdk/directory/quickstart.py
+++ b/admin_sdk/directory/quickstart.py
@@ -14,13 +14,13 @@
 
 # [START admin_sdk_directory_quickstart]
 from __future__ import print_function
-import pickle
 import os.path
 from googleapiclient.discovery import build
 from google_auth_oauthlib.flow import InstalledAppFlow
 from google.auth.transport.requests import Request
+from google.oauth2.credentials import Credentials
 
-# If modifying these scopes, delete the file token.pickle.
+# If modifying these scopes, delete the file token.json.
 SCOPES = ['https://www.googleapis.com/auth/admin.directory.user']
 
 def main():
@@ -28,12 +28,11 @@ def main():
     Prints the emails and names of the first 10 users in the domain.
     """
     creds = None
-    # The file token.pickle stores the user's access and refresh tokens, and is
+    # The file token.json stores the user's access and refresh tokens, and is
     # created automatically when the authorization flow completes for the first
     # time.
-    if os.path.exists('token.pickle'):
-        with open('token.pickle', 'rb') as token:
-            creds = pickle.load(token)
+    if os.path.exists('token.json'):
+        creds = Credentials.from_authorized_user_file('token.json', SCOPES)
     # If there are no (valid) credentials available, let the user log in.
     if not creds or not creds.valid:
         if creds and creds.expired and creds.refresh_token:
@@ -43,8 +42,8 @@ def main():
                 'credentials.json', SCOPES)
             creds = flow.run_local_server(port=0)
         # Save the credentials for the next run
-        with open('token.pickle', 'wb') as token:
-            pickle.dump(creds, token)
+        with open('token.json', 'w') as token:
+            token.write(creds.to_json())
 
     service = build('admin', 'directory_v1', credentials=creds)
 
diff --git a/admin_sdk/reports/quickstart.py b/admin_sdk/reports/quickstart.py
index 29bc20dd..2b6d4d06 100644
--- a/admin_sdk/reports/quickstart.py
+++ b/admin_sdk/reports/quickstart.py
@@ -14,13 +14,13 @@
 
 # [START admin_sdk_reports_quickstart]
 from __future__ import print_function
-import pickle
 import os.path
 from googleapiclient.discovery import build
 from google_auth_oauthlib.flow import InstalledAppFlow
 from google.auth.transport.requests import Request
+from google.oauth2.credentials import Credentials
 
-# If modifying these scopes, delete the file token.pickle.
+# If modifying these scopes, delete the file token.json.
 SCOPES = ['https://www.googleapis.com/auth/admin.reports.audit.readonly']
 
 def main():
@@ -28,12 +28,11 @@ def main():
     Prints the time, email, and name of the last 10 login events in the domain.
     """
     creds = None
-    # The file token.pickle stores the user's access and refresh tokens, and is
+    # The file token.json stores the user's access and refresh tokens, and is
     # created automatically when the authorization flow completes for the first
     # time.
-    if os.path.exists('token.pickle'):
-        with open('token.pickle', 'rb') as token:
-            creds = pickle.load(token)
+    if os.path.exists('token.json'):
+        creds = Credentials.from_authorized_user_file('token.json', SCOPES)
     # If there are no (valid) credentials available, let the user log in.
     if not creds or not creds.valid:
         if creds and creds.expired and creds.refresh_token:
@@ -43,8 +42,8 @@ def main():
                 'credentials.json', SCOPES)
             creds = flow.run_local_server(port=0)
         # Save the credentials for the next run
-        with open('token.pickle', 'wb') as token:
-            pickle.dump(creds, token)
+        with open('token.json', 'w') as token:
+            token.write(creds.to_json())
 
     service = build('admin', 'reports_v1', credentials=creds)
 
diff --git a/admin_sdk/reseller/quickstart.py b/admin_sdk/reseller/quickstart.py
index 6fb733d0..316edcd2 100644
--- a/admin_sdk/reseller/quickstart.py
+++ b/admin_sdk/reseller/quickstart.py
@@ -14,13 +14,13 @@
 
 # [START admin_sdk_reseller_quickstart]
 from __future__ import print_function
-import pickle
 import os.path
 from googleapiclient.discovery import build
 from google_auth_oauthlib.flow import InstalledAppFlow
 from google.auth.transport.requests import Request
+from google.oauth2.credentials import Credentials
 
-# If modifying these scopes, delete the file token.pickle.
+# If modifying these scopes, delete the file token.json.
 SCOPES = ['https://www.googleapis.com/auth/apps.order']
 
 def main():
@@ -28,12 +28,11 @@ def main():
     and plan name of the first 10 subscriptions managed by the domain.
     """
     creds = None
-    # The file token.pickle stores the user's access and refresh tokens, and is
+    # The file token.json stores the user's access and refresh tokens, and is
     # created automatically when the authorization flow completes for the first
     # time.
-    if os.path.exists('token.pickle'):
-        with open('token.pickle', 'rb') as token:
-            creds = pickle.load(token)
+    if os.path.exists('token.json'):
+        creds = Credentials.from_authorized_user_file('token.json', SCOPES)
     # If there are no (valid) credentials available, let the user log in.
     if not creds or not creds.valid:
         if creds and creds.expired and creds.refresh_token:
@@ -43,8 +42,8 @@ def main():
                 'credentials.json', SCOPES)
             creds = flow.run_local_server(port=0)
         # Save the credentials for the next run
-        with open('token.pickle', 'wb') as token:
-            pickle.dump(creds, token)
+        with open('token.json', 'w') as token:
+            token.write(creds.to_json())
 
     service = build('reseller', 'v1', credentials=creds)
 
diff --git a/apps_script/quickstart/quickstart.py b/apps_script/quickstart/quickstart.py
index 1d3005a0..c8650dea 100644
--- a/apps_script/quickstart/quickstart.py
+++ b/apps_script/quickstart/quickstart.py
@@ -19,14 +19,14 @@
 project, and log the script's URL to the user.
 """
 from __future__ import print_function
-import pickle
 import os.path
 from googleapiclient import errors
 from googleapiclient.discovery import build
 from google_auth_oauthlib.flow import InstalledAppFlow
 from google.auth.transport.requests import Request
+from google.oauth2.credentials import Credentials
 
-# If modifying these scopes, delete the file token.pickle.
+# If modifying these scopes, delete the file token.json.
 SCOPES = ['https://www.googleapis.com/auth/script.projects']
 
 SAMPLE_CODE = '''
@@ -46,12 +46,11 @@ def main():
     """Calls the Apps Script API.
     """
     creds = None
-    # The file token.pickle stores the user's access and refresh tokens, and is
+    # The file token.json stores the user's access and refresh tokens, and is
     # created automatically when the authorization flow completes for the first
     # time.
-    if os.path.exists('token.pickle'):
-        with open('token.pickle', 'rb') as token:
-            creds = pickle.load(token)
+    if os.path.exists('token.json'):
+        creds = Credentials.from_authorized_user_file('token.json', SCOPES)
     # If there are no (valid) credentials available, let the user log in.
     if not creds or not creds.valid:
         if creds and creds.expired and creds.refresh_token:
@@ -61,8 +60,8 @@ def main():
                 'credentials.json', SCOPES)
             creds = flow.run_local_server(port=0)
         # Save the credentials for the next run
-        with open('token.pickle', 'wb') as token:
-            pickle.dump(creds, token)
+        with open('token.json', 'w') as token:
+            token.write(creds.to_json())
 
     service = build('script', 'v1', credentials=creds)
 
diff --git a/calendar/quickstart/quickstart.py b/calendar/quickstart/quickstart.py
index 192a81ec..67d837dd 100644
--- a/calendar/quickstart/quickstart.py
+++ b/calendar/quickstart/quickstart.py
@@ -15,13 +15,13 @@
 # [START calendar_quickstart]
 from __future__ import print_function
 import datetime
-import pickle
 import os.path
 from googleapiclient.discovery import build
 from google_auth_oauthlib.flow import InstalledAppFlow
 from google.auth.transport.requests import Request
+from google.oauth2.credentials import Credentials
 
-# If modifying these scopes, delete the file token.pickle.
+# If modifying these scopes, delete the file token.json.
 SCOPES = ['https://www.googleapis.com/auth/calendar.readonly']
 
 
@@ -30,12 +30,11 @@ def main():
     Prints the start and name of the next 10 events on the user's calendar.
     """
     creds = None
-    # The file token.pickle stores the user's access and refresh tokens, and is
+    # The file token.json stores the user's access and refresh tokens, and is
     # created automatically when the authorization flow completes for the first
     # time.
-    if os.path.exists('token.pickle'):
-        with open('token.pickle', 'rb') as token:
-            creds = pickle.load(token)
+    if os.path.exists('token.json'):
+        creds = Credentials.from_authorized_user_file('token.json', SCOPES)
     # If there are no (valid) credentials available, let the user log in.
     if not creds or not creds.valid:
         if creds and creds.expired and creds.refresh_token:
@@ -45,8 +44,8 @@ def main():
                 'credentials.json', SCOPES)
             creds = flow.run_local_server(port=0)
         # Save the credentials for the next run
-        with open('token.pickle', 'wb') as token:
-            pickle.dump(creds, token)
+        with open('token.json', 'w') as token:
+            token.write(creds.to_json())
 
     service = build('calendar', 'v3', credentials=creds)
 
diff --git a/classroom/quickstart/quickstart.py b/classroom/quickstart/quickstart.py
index 3ec54884..35646557 100644
--- a/classroom/quickstart/quickstart.py
+++ b/classroom/quickstart/quickstart.py
@@ -14,13 +14,13 @@
 
 # [START classroom_quickstart]
 from __future__ import print_function
-import pickle
 import os.path
 from googleapiclient.discovery import build
 from google_auth_oauthlib.flow import InstalledAppFlow
 from google.auth.transport.requests import Request
+from google.oauth2.credentials import Credentials
 
-# If modifying these scopes, delete the file token.pickle.
+# If modifying these scopes, delete the file token.json.
 SCOPES = ['https://www.googleapis.com/auth/classroom.courses.readonly']
 
 def main():
@@ -28,12 +28,11 @@ def main():
     Prints the names of the first 10 courses the user has access to.
     """
     creds = None
-    # The file token.pickle stores the user's access and refresh tokens, and is
+    # The file token.json stores the user's access and refresh tokens, and is
     # created automatically when the authorization flow completes for the first
     # time.
-    if os.path.exists('token.pickle'):
-        with open('token.pickle', 'rb') as token:
-            creds = pickle.load(token)
+    if os.path.exists('token.json'):
+        creds = Credentials.from_authorized_user_file('token.json', SCOPES)
     # If there are no (valid) credentials available, let the user log in.
     if not creds or not creds.valid:
         if creds and creds.expired and creds.refresh_token:
@@ -43,8 +42,8 @@ def main():
                 'credentials.json', SCOPES)
             creds = flow.run_local_server(port=0)
         # Save the credentials for the next run
-        with open('token.pickle', 'wb') as token:
-            pickle.dump(creds, token)
+        with open('token.json', 'w') as token:
+            token.write(creds.to_json())
 
     service = build('classroom', 'v1', credentials=creds)
 
diff --git a/docs/quickstart/quickstart.py b/docs/quickstart/quickstart.py
index 7c08fb0a..0dd687e9 100644
--- a/docs/quickstart/quickstart.py
+++ b/docs/quickstart/quickstart.py
@@ -14,13 +14,13 @@
 
 # [START docs_quickstart]
 from __future__ import print_function
-import pickle
 import os.path
 from googleapiclient.discovery import build
 from google_auth_oauthlib.flow import InstalledAppFlow
 from google.auth.transport.requests import Request
+from google.oauth2.credentials import Credentials
 
-# If modifying these scopes, delete the file token.pickle.
+# If modifying these scopes, delete the file token.json.
 SCOPES = ['https://www.googleapis.com/auth/documents.readonly']
 
 # The ID of a sample document.
@@ -31,12 +31,11 @@ def main():
     Prints the title of a sample document.
     """
     creds = None
-    # The file token.pickle stores the user's access and refresh tokens, and is
+    # The file token.json stores the user's access and refresh tokens, and is
     # created automatically when the authorization flow completes for the first
     # time.
-    if os.path.exists('token.pickle'):
-        with open('token.pickle', 'rb') as token:
-            creds = pickle.load(token)
+    if os.path.exists('token.json'):
+        creds = Credentials.from_authorized_user_file('token.json', SCOPES)
     # If there are no (valid) credentials available, let the user log in.
     if not creds or not creds.valid:
         if creds and creds.expired and creds.refresh_token:
@@ -46,8 +45,8 @@ def main():
                 'credentials.json', SCOPES)
             creds = flow.run_local_server(port=0)
         # Save the credentials for the next run
-        with open('token.pickle', 'wb') as token:
-            pickle.dump(creds, token)
+        with open('token.json', 'w') as token:
+            token.write(creds.to_json())
 
     service = build('docs', 'v1', credentials=creds)
 
diff --git a/drive/activity-v2/quickstart.py b/drive/activity-v2/quickstart.py
index 08cc39e7..292999a5 100644
--- a/drive/activity-v2/quickstart.py
+++ b/drive/activity-v2/quickstart.py
@@ -14,13 +14,13 @@
 
 # [START drive_activity_v2_quickstart]
 from __future__ import print_function
-import pickle
 import os.path
 from googleapiclient.discovery import build
 from google_auth_oauthlib.flow import InstalledAppFlow
 from google.auth.transport.requests import Request
+from google.oauth2.credentials import Credentials
 
-# If modifying these scopes, delete the file token.pickle.
+# If modifying these scopes, delete the file token.json.
 SCOPES = ['https://www.googleapis.com/auth/drive.activity.readonly']
 
 
@@ -30,12 +30,11 @@ def main():
     Prints information about the last 10 events that occured the user's Drive.
     """
     creds = None
-    # The file token.pickle stores the user's access and refresh tokens, and is
+    # The file token.json stores the user's access and refresh tokens, and is
     # created automatically when the authorization flow completes for the first
     # time.
-    if os.path.exists('token.pickle'):
-        with open('token.pickle', 'rb') as token:
-            creds = pickle.load(token)
+    if os.path.exists('token.json'):
+        creds = Credentials.from_authorized_user_file('token.json', SCOPES)
     # If there are no (valid) credentials available, let the user log in.
     if not creds or not creds.valid:
         if creds and creds.expired and creds.refresh_token:
@@ -45,8 +44,8 @@ def main():
                 'credentials.json', SCOPES)
             creds = flow.run_local_server(port=0)
         # Save the credentials for the next run
-        with open('token.pickle', 'wb') as token:
-            pickle.dump(creds, token)
+        with open('token.json', 'w') as token:
+            token.write(creds.to_json())
 
     service = build('driveactivity', 'v2', credentials=creds)
 
diff --git a/drive/activity/quickstart.py b/drive/activity/quickstart.py
index e1a2c3b1..96a40a0e 100644
--- a/drive/activity/quickstart.py
+++ b/drive/activity/quickstart.py
@@ -15,13 +15,13 @@
 # [START drive_activity_quickstart]
 from __future__ import print_function
 import datetime
-import pickle
 import os.path
 from googleapiclient.discovery import build
 from google_auth_oauthlib.flow import InstalledAppFlow
 from google.auth.transport.requests import Request
+from google.oauth2.credentials import Credentials
 
-# If modifying these scopes, delete the file token.pickle.
+# If modifying these scopes, delete the file token.json.
 SCOPES = ['https://www.googleapis.com/auth/activity']
 
 def main():
@@ -29,12 +29,11 @@ def main():
     Prints information about the last 10 events that occured the user's Drive.
     """
     creds = None
-    # The file token.pickle stores the user's access and refresh tokens, and is
+    # The file token.json stores the user's access and refresh tokens, and is
     # created automatically when the authorization flow completes for the first
     # time.
-    if os.path.exists('token.pickle'):
-        with open('token.pickle', 'rb') as token:
-            creds = pickle.load(token)
+    if os.path.exists('token.json'):
+        creds = Credentials.from_authorized_user_file('token.json', SCOPES)
     # If there are no (valid) credentials available, let the user log in.
     if not creds or not creds.valid:
         if creds and creds.expired and creds.refresh_token:
@@ -44,8 +43,8 @@ def main():
                 'credentials.json', SCOPES)
             creds = flow.run_local_server(port=0)
         # Save the credentials for the next run
-        with open('token.pickle', 'wb') as token:
-            pickle.dump(creds, token)
+        with open('token.json', 'w') as token:
+            token.write(creds.to_json())
 
     service = build('appsactivity', 'v1', credentials=creds)
 
diff --git a/drive/quickstart/quickstart.py b/drive/quickstart/quickstart.py
index dd0767c9..6267ff42 100644
--- a/drive/quickstart/quickstart.py
+++ b/drive/quickstart/quickstart.py
@@ -14,13 +14,13 @@
 
 # [START drive_quickstart]
 from __future__ import print_function
-import pickle
 import os.path
 from googleapiclient.discovery import build
 from google_auth_oauthlib.flow import InstalledAppFlow
 from google.auth.transport.requests import Request
+from google.oauth2.credentials import Credentials
 
-# If modifying these scopes, delete the file token.pickle.
+# If modifying these scopes, delete the file token.json.
 SCOPES = ['https://www.googleapis.com/auth/drive.metadata.readonly']
 
 def main():
@@ -28,12 +28,11 @@ def main():
     Prints the names and ids of the first 10 files the user has access to.
     """
     creds = None
-    # The file token.pickle stores the user's access and refresh tokens, and is
+    # The file token.json stores the user's access and refresh tokens, and is
     # created automatically when the authorization flow completes for the first
     # time.
-    if os.path.exists('token.pickle'):
-        with open('token.pickle', 'rb') as token:
-            creds = pickle.load(token)
+    if os.path.exists('token.json'):
+        creds = Credentials.from_authorized_user_file('token.json', SCOPES)
     # If there are no (valid) credentials available, let the user log in.
     if not creds or not creds.valid:
         if creds and creds.expired and creds.refresh_token:
@@ -43,8 +42,8 @@ def main():
                 'credentials.json', SCOPES)
             creds = flow.run_local_server(port=0)
         # Save the credentials for the next run
-        with open('token.pickle', 'wb') as token:
-            pickle.dump(creds, token)
+        with open('token.json', 'w') as token:
+            token.write(creds.to_json())
 
     service = build('drive', 'v3', credentials=creds)
 
diff --git a/gmail/quickstart/quickstart.py b/gmail/quickstart/quickstart.py
index 92986897..5e342669 100644
--- a/gmail/quickstart/quickstart.py
+++ b/gmail/quickstart/quickstart.py
@@ -14,13 +14,13 @@
 
 # [START gmail_quickstart]
 from __future__ import print_function
-import pickle
 import os.path
 from googleapiclient.discovery import build
 from google_auth_oauthlib.flow import InstalledAppFlow
 from google.auth.transport.requests import Request
+from google.oauth2.credentials import Credentials
 
-# If modifying these scopes, delete the file token.pickle.
+# If modifying these scopes, delete the file token.json.
 SCOPES = ['https://www.googleapis.com/auth/gmail.readonly']
 
 def main():
@@ -28,12 +28,11 @@ def main():
     Lists the user's Gmail labels.
     """
     creds = None
-    # The file token.pickle stores the user's access and refresh tokens, and is
+    # The file token.json stores the user's access and refresh tokens, and is
     # created automatically when the authorization flow completes for the first
     # time.
-    if os.path.exists('token.pickle'):
-        with open('token.pickle', 'rb') as token:
-            creds = pickle.load(token)
+    if os.path.exists('token.json'):
+        creds = Credentials.from_authorized_user_file('token.json', SCOPES)
     # If there are no (valid) credentials available, let the user log in.
     if not creds or not creds.valid:
         if creds and creds.expired and creds.refresh_token:
@@ -43,8 +42,8 @@ def main():
                 'credentials.json', SCOPES)
             creds = flow.run_local_server(port=0)
         # Save the credentials for the next run
-        with open('token.pickle', 'wb') as token:
-            pickle.dump(creds, token)
+        with open('token.json', 'w') as token:
+            token.write(creds.to_json())
 
     service = build('gmail', 'v1', credentials=creds)
 
diff --git a/people/quickstart/quickstart.py b/people/quickstart/quickstart.py
index e43ec320..dcd52210 100644
--- a/people/quickstart/quickstart.py
+++ b/people/quickstart/quickstart.py
@@ -14,13 +14,13 @@
 
 # [START people_quickstart]
 from __future__ import print_function
-import pickle
 import os.path
 from googleapiclient.discovery import build
 from google_auth_oauthlib.flow import InstalledAppFlow
 from google.auth.transport.requests import Request
+from google.oauth2.credentials import Credentials
 
-# If modifying these scopes, delete the file token.pickle.
+# If modifying these scopes, delete the file token.json.
 SCOPES = ['https://www.googleapis.com/auth/contacts.readonly']
 
 def main():
@@ -28,12 +28,11 @@ def main():
     Prints the name of the first 10 connections.
     """
     creds = None
-    # The file token.pickle stores the user's access and refresh tokens, and is
+    # The file token.json stores the user's access and refresh tokens, and is
     # created automatically when the authorization flow completes for the first
     # time.
-    if os.path.exists('token.pickle'):
-        with open('token.pickle', 'rb') as token:
-            creds = pickle.load(token)
+    if os.path.exists('token.json'):
+        creds = Credentials.from_authorized_user_file('token.json', SCOPES)
     # If there are no (valid) credentials available, let the user log in.
     if not creds or not creds.valid:
         if creds and creds.expired and creds.refresh_token:
@@ -43,8 +42,8 @@ def main():
                 'credentials.json', SCOPES)
             creds = flow.run_local_server(port=0)
         # Save the credentials for the next run
-        with open('token.pickle', 'wb') as token:
-            pickle.dump(creds, token)
+        with open('token.json', 'w') as token:
+            token.write(creds.to_json())
 
     service = build('people', 'v1', credentials=creds)
 
diff --git a/sheets/quickstart/quickstart.py b/sheets/quickstart/quickstart.py
index c782e563..7dff04ab 100644
--- a/sheets/quickstart/quickstart.py
+++ b/sheets/quickstart/quickstart.py
@@ -14,13 +14,13 @@
 
 # [START sheets_quickstart]
 from __future__ import print_function
-import pickle
 import os.path
 from googleapiclient.discovery import build
 from google_auth_oauthlib.flow import InstalledAppFlow
 from google.auth.transport.requests import Request
+from google.oauth2.credentials import Credentials
 
-# If modifying these scopes, delete the file token.pickle.
+# If modifying these scopes, delete the file token.json.
 SCOPES = ['https://www.googleapis.com/auth/spreadsheets.readonly']
 
 # The ID and range of a sample spreadsheet.
@@ -32,12 +32,11 @@ def main():
     Prints values from a sample spreadsheet.
     """
     creds = None
-    # The file token.pickle stores the user's access and refresh tokens, and is
+    # The file token.json stores the user's access and refresh tokens, and is
     # created automatically when the authorization flow completes for the first
     # time.
-    if os.path.exists('token.pickle'):
-        with open('token.pickle', 'rb') as token:
-            creds = pickle.load(token)
+    if os.path.exists('token.json'):
+        creds = Credentials.from_authorized_user_file('token.json', SCOPES)
     # If there are no (valid) credentials available, let the user log in.
     if not creds or not creds.valid:
         if creds and creds.expired and creds.refresh_token:
@@ -47,8 +46,8 @@ def main():
                 'credentials.json', SCOPES)
             creds = flow.run_local_server(port=0)
         # Save the credentials for the next run
-        with open('token.pickle', 'wb') as token:
-            pickle.dump(creds, token)
+        with open('token.json', 'w') as token:
+            token.write(creds.to_json())
 
     service = build('sheets', 'v4', credentials=creds)
 
diff --git a/slides/quickstart/quickstart.py b/slides/quickstart/quickstart.py
index fbb4b5a8..e86e2487 100644
--- a/slides/quickstart/quickstart.py
+++ b/slides/quickstart/quickstart.py
@@ -14,13 +14,13 @@
 
 # [START slides_quickstart]
 from __future__ import print_function
-import pickle
 import os.path
 from googleapiclient.discovery import build
 from google_auth_oauthlib.flow import InstalledAppFlow
 from google.auth.transport.requests import Request
+from google.oauth2.credentials import Credentials
 
-# If modifying these scopes, delete the file token.pickle.
+# If modifying these scopes, delete the file token.json.
 SCOPES = ['https://www.googleapis.com/auth/presentations.readonly']
 
 # The ID of a sample presentation.
@@ -31,12 +31,11 @@ def main():
     Prints the number of slides and elments in a sample presentation.
     """
     creds = None
-    # The file token.pickle stores the user's access and refresh tokens, and is
+    # The file token.json stores the user's access and refresh tokens, and is
     # created automatically when the authorization flow completes for the first
     # time.
-    if os.path.exists('token.pickle'):
-        with open('token.pickle', 'rb') as token:
-            creds = pickle.load(token)
+    if os.path.exists('token.json'):
+        creds = Credentials.from_authorized_user_file('token.json', SCOPES)
     # If there are no (valid) credentials available, let the user log in.
     if not creds or not creds.valid:
         if creds and creds.expired and creds.refresh_token:
@@ -46,8 +45,8 @@ def main():
                 'credentials.json', SCOPES)
             creds = flow.run_local_server(port=0)
         # Save the credentials for the next run
-        with open('token.pickle', 'wb') as token:
-            pickle.dump(creds, token)
+        with open('token.json', 'w') as token:
+            token.write(creds.to_json())
 
     service = build('slides', 'v1', credentials=creds)
 
diff --git a/tasks/quickstart/quickstart.py b/tasks/quickstart/quickstart.py
index 564acf6b..fcedfe88 100644
--- a/tasks/quickstart/quickstart.py
+++ b/tasks/quickstart/quickstart.py
@@ -14,13 +14,13 @@
 
 # [START tasks_quickstart]
 from __future__ import print_function
-import pickle
 import os.path
 from googleapiclient.discovery import build
 from google_auth_oauthlib.flow import InstalledAppFlow
 from google.auth.transport.requests import Request
+from google.oauth2.credentials import Credentials
 
-# If modifying these scopes, delete the file token.pickle.
+# If modifying these scopes, delete the file token.json.
 SCOPES = ['https://www.googleapis.com/auth/tasks.readonly']
 
 def main():
@@ -28,12 +28,11 @@ def main():
     Prints the title and ID of the first 10 task lists.
     """
     creds = None
-    # The file token.pickle stores the user's access and refresh tokens, and is
+    # The file token.json stores the user's access and refresh tokens, and is
     # created automatically when the authorization flow completes for the first
     # time.
-    if os.path.exists('token.pickle'):
-        with open('token.pickle', 'rb') as token:
-            creds = pickle.load(token)
+    if os.path.exists('token.json'):
+        creds = Credentials.from_authorized_user_file('token.json', SCOPES)
     # If there are no (valid) credentials available, let the user log in.
     if not creds or not creds.valid:
         if creds and creds.expired and creds.refresh_token:
@@ -43,8 +42,8 @@ def main():
                 'credentials.json', SCOPES)
             creds = flow.run_local_server(port=0)
         # Save the credentials for the next run
-        with open('token.pickle', 'wb') as token:
-            pickle.dump(creds, token)
+        with open('token.json', 'w') as token:
+            token.write(creds.to_json())
 
     service = build('tasks', 'v1', credentials=creds)
 
diff --git a/vault/quickstart/quickstart.py b/vault/quickstart/quickstart.py
index e586626c..851f51be 100644
--- a/vault/quickstart/quickstart.py
+++ b/vault/quickstart/quickstart.py
@@ -14,13 +14,13 @@
 
 # [START vault_quickstart]
 from __future__ import print_function
-import pickle
 import os.path
 from googleapiclient.discovery import build
 from google_auth_oauthlib.flow import InstalledAppFlow
 from google.auth.transport.requests import Request
+from google.oauth2.credentials import Credentials
 
-# If modifying these scopes, delete the file token.pickle.
+# If modifying these scopes, delete the file token.json.
 SCOPES = ['https://www.googleapis.com/auth/ediscovery']
 
 def main():
@@ -28,12 +28,11 @@ def main():
     Prints the names and IDs of the first 10 matters in Vault.
     """
     creds = None
-    # The file token.pickle stores the user's access and refresh tokens, and is
+    # The file token.json stores the user's access and refresh tokens, and is
     # created automatically when the authorization flow completes for the first
     # time.
-    if os.path.exists('token.pickle'):
-        with open('token.pickle', 'rb') as token:
-            creds = pickle.load(token)
+    if os.path.exists('token.json'):
+        creds = Credentials.from_authorized_user_file('token.json', SCOPES)
     # If there are no (valid) credentials available, let the user log in.
     if not creds or not creds.valid:
         if creds and creds.expired and creds.refresh_token:
@@ -43,8 +42,8 @@ def main():
                 'credentials.json', SCOPES)
             creds = flow.run_local_server(port=0)
         # Save the credentials for the next run
-        with open('token.pickle', 'wb') as token:
-            pickle.dump(creds, token)
+        with open('token.json', 'w') as token:
+            token.write(creds.to_json())
 
     service = build('vault', 'v1', credentials=creds)