Google OAuth 2.0 / OIDC + Gmail, Calendar & Drive Emulator
OAuth 2.0 and OpenID Connect emulation with authorization code flow, PKCE support, ID tokens, OIDC discovery, refresh tokens, plus Gmail, Google Calendar, and Google Drive REST API surfaces.
Start
# Google only
npx emulate --service google
# Default port
# http://localhost:4002Or programmatically:
import { createEmulator } from 'emulate'
const google = await createEmulator({ service: 'google', port: 4002 })
// google.url === 'http://localhost:4002'Pointing Your App at the Emulator
Environment Variable
GOOGLE_EMULATOR_URL=http://localhost:4002OAuth URL Mapping
| Real Google URL | Emulator URL |
|---|---|
https://accounts.google.com/o/oauth2/v2/auth | $GOOGLE_EMULATOR_URL/o/oauth2/v2/auth |
https://oauth2.googleapis.com/token | $GOOGLE_EMULATOR_URL/oauth2/token |
https://www.googleapis.com/oauth2/v2/userinfo | $GOOGLE_EMULATOR_URL/oauth2/v2/userinfo |
https://accounts.google.com/.well-known/openid-configuration | $GOOGLE_EMULATOR_URL/.well-known/openid-configuration |
https://www.googleapis.com/oauth2/v3/certs | $GOOGLE_EMULATOR_URL/oauth2/v3/certs |
https://gmail.googleapis.com/gmail/v1/... | $GOOGLE_EMULATOR_URL/gmail/v1/... |
https://www.googleapis.com/calendar/v3/... | $GOOGLE_EMULATOR_URL/calendar/v3/... |
https://www.googleapis.com/drive/v3/... | $GOOGLE_EMULATOR_URL/drive/v3/... |
google-auth-library (Node.js)
import { OAuth2Client } from 'google-auth-library'
const GOOGLE_URL = process.env.GOOGLE_EMULATOR_URL ?? 'https://accounts.google.com'
const client = new OAuth2Client({
clientId: process.env.GOOGLE_CLIENT_ID,
clientSecret: process.env.GOOGLE_CLIENT_SECRET,
redirectUri: 'http://localhost:3000/api/auth/callback/google',
})
const emulatorAuthorizeUrl = `${GOOGLE_URL}/o/oauth2/v2/auth?client_id=${process.env.GOOGLE_CLIENT_ID}&redirect_uri=...&scope=openid+email+profile&response_type=code&state=...`Auth.js / NextAuth.js
import Google from '@auth/core/providers/google'
Google({
clientId: process.env.GOOGLE_CLIENT_ID,
clientSecret: process.env.GOOGLE_CLIENT_SECRET,
authorization: {
url: `${process.env.GOOGLE_EMULATOR_URL}/o/oauth2/v2/auth`,
params: { scope: 'openid email profile' },
},
token: {
url: `${process.env.GOOGLE_EMULATOR_URL}/oauth2/token`,
},
userinfo: {
url: `${process.env.GOOGLE_EMULATOR_URL}/oauth2/v2/userinfo`,
},
})Passport.js
import { Strategy as GoogleStrategy } from 'passport-google-oauth20'
const GOOGLE_URL = process.env.GOOGLE_EMULATOR_URL ?? 'https://accounts.google.com'
new GoogleStrategy({
clientID: process.env.GOOGLE_CLIENT_ID,
clientSecret: process.env.GOOGLE_CLIENT_SECRET,
callbackURL: 'http://localhost:3000/api/auth/callback/google',
authorizationURL: `${GOOGLE_URL}/o/oauth2/v2/auth`,
tokenURL: `${GOOGLE_URL}/oauth2/token`,
userProfileURL: `${GOOGLE_URL}/oauth2/v2/userinfo`,
}, verifyCallback)Seed Config
google:
users:
- email: testuser@gmail.com
name: Test User
given_name: Test
family_name: User
picture: https://lh3.googleusercontent.com/a/default-user
email_verified: true
locale: en
- email: dev@example.com
name: Developer
- email: admin@acme.com
name: Admin
hd: acme.com
oauth_clients:
- client_id: my-client-id.apps.googleusercontent.com
client_secret: GOCSPX-secret
name: My App
redirect_uris:
- http://localhost:3000/api/auth/callback/google
labels:
- id: Label_ops
user_email: testuser@gmail.com
name: Ops/Review
color_background: "#DDEEFF"
color_text: "#111111"
messages:
- id: msg_welcome
user_email: testuser@gmail.com
thread_id: thr_welcome
from: "welcome@example.com"
to: testuser@gmail.com
subject: Welcome to the Gmail emulator
body_text: You can now test Gmail flows locally.
label_ids: [INBOX, UNREAD, CATEGORY_UPDATES]
date: "2025-01-04T10:00:00.000Z"
calendars:
- id: primary
user_email: testuser@gmail.com
summary: testuser@gmail.com
primary: true
selected: true
time_zone: UTC
calendar_events:
- id: evt_kickoff
user_email: testuser@gmail.com
calendar_id: primary
summary: Project Kickoff
start_date_time: "2025-01-10T09:00:00.000Z"
end_date_time: "2025-01-10T09:30:00.000Z"
attendees:
- email: testuser@gmail.com
display_name: Test User
conference_entry_points:
- entry_point_type: video
uri: https://meet.google.com/example
label: Google Meet
hangout_link: https://meet.google.com/example
drive_items:
- id: drv_docs
user_email: testuser@gmail.com
name: Docs
mime_type: application/vnd.google-apps.folder
parent_ids: [root]
- id: drv_readme
user_email: testuser@gmail.com
name: README.md
mime_type: text/markdown
parent_ids: [drv_docs]
data: "# Hello World"When no OAuth clients are configured, the emulator accepts any client_id. With clients configured, strict validation is enforced for client_id, client_secret, and redirect_uri.
Hosted domain (hd) claim
Google Workspace accounts include an hd claim in ID tokens and userinfo responses identifying the user's hosted domain. The emulator derives this automatically from the user's email domain. Consumer domains (gmail.com, googlemail.com) omit the claim, matching real Google behavior.
To override the derived value, set hd on a seeded user. To suppress the claim entirely, set hd to an empty string.
OAuth / OIDC Endpoints
OIDC Discovery
curl http://localhost:4002/.well-known/openid-configurationJWKS
curl http://localhost:4002/oauth2/v3/certsReturns {"keys": []}. ID tokens are signed with HS256 using an internal secret.
Authorization
# Browser flow: redirects to a user picker page
curl -v "http://localhost:4002/o/oauth2/v2/auth?\
client_id=my-client-id.apps.googleusercontent.com&\
redirect_uri=http://localhost:3000/api/auth/callback/google&\
scope=openid+email+profile&\
response_type=code&\
state=random-state&\
nonce=random-nonce"Supports code_challenge and code_challenge_method for PKCE.
Token Exchange
curl -X POST http://localhost:4002/oauth2/token \
-H "Content-Type: application/x-www-form-urlencoded" \
-d "code=<authorization_code>&\
client_id=my-client-id.apps.googleusercontent.com&\
client_secret=GOCSPX-secret&\
redirect_uri=http://localhost:3000/api/auth/callback/google&\
grant_type=authorization_code"Also accepts application/json body. Returns:
{
"access_token": "google_...",
"refresh_token": "google_refresh_...",
"id_token": "<jwt>",
"token_type": "Bearer",
"expires_in": 3600,
"scope": "openid email profile"
}Refresh Token
curl -X POST http://localhost:4002/oauth2/token \
-H "Content-Type: application/x-www-form-urlencoded" \
-d "refresh_token=google_refresh_...&\
client_id=my-client-id.apps.googleusercontent.com&\
client_secret=GOCSPX-secret&\
grant_type=refresh_token"Returns a new access_token (no new refresh_token or id_token on refresh).
User Info
curl http://localhost:4002/oauth2/v2/userinfo \
-H "Authorization: Bearer google_..."Token Revocation
curl -X POST http://localhost:4002/oauth2/revoke \
-H "Content-Type: application/x-www-form-urlencoded" \
-d "token=google_..."Gmail API
All Gmail endpoints are under /gmail/v1/users/:userId/... where :userId is me or the authenticated user's email.
Messages
# List messages (filter by labels, search query)
curl "http://localhost:4002/gmail/v1/users/me/messages?labelIds=INBOX&q=from:welcome&maxResults=10" \
-H "Authorization: Bearer $TOKEN"
# Get message (format: full, metadata, minimal, raw)
curl "http://localhost:4002/gmail/v1/users/me/messages/msg_welcome?format=full" \
-H "Authorization: Bearer $TOKEN"
# Send message
curl -X POST http://localhost:4002/gmail/v1/users/me/messages/send \
-H "Authorization: Bearer $TOKEN" \
-H "Content-Type: application/json" \
-d '{"to": "someone@example.com", "subject": "Hello", "body_text": "Hi there"}'
# Insert message (bypass send)
curl -X POST http://localhost:4002/gmail/v1/users/me/messages \
-H "Authorization: Bearer $TOKEN" \
-H "Content-Type: application/json" \
-d '{"to": "test@example.com", "from": "me@example.com", "subject": "Test", "body_text": "Body", "labelIds": ["INBOX"]}'
# Import message
curl -X POST http://localhost:4002/gmail/v1/users/me/messages/import \
-H "Authorization: Bearer $TOKEN" \
-H "Content-Type: application/json" \
-d '{"to": "test@example.com", "from": "external@example.com", "subject": "Imported", "body_text": "Content"}'
# Modify labels on a message
curl -X POST http://localhost:4002/gmail/v1/users/me/messages/msg_welcome/modify \
-H "Authorization: Bearer $TOKEN" \
-H "Content-Type: application/json" \
-d '{"addLabelIds": ["STARRED"], "removeLabelIds": ["UNREAD"]}'
# Trash / untrash
curl -X POST http://localhost:4002/gmail/v1/users/me/messages/msg_welcome/trash \
-H "Authorization: Bearer $TOKEN"
curl -X POST http://localhost:4002/gmail/v1/users/me/messages/msg_welcome/untrash \
-H "Authorization: Bearer $TOKEN"
# Delete permanently
curl -X DELETE http://localhost:4002/gmail/v1/users/me/messages/msg_welcome \
-H "Authorization: Bearer $TOKEN"
# Batch modify
curl -X POST http://localhost:4002/gmail/v1/users/me/messages/batchModify \
-H "Authorization: Bearer $TOKEN" \
-H "Content-Type: application/json" \
-d '{"ids": ["msg_welcome", "msg_build"], "addLabelIds": ["STARRED"]}'
# Batch delete
curl -X POST http://localhost:4002/gmail/v1/users/me/messages/batchDelete \
-H "Authorization: Bearer $TOKEN" \
-H "Content-Type: application/json" \
-d '{"ids": ["msg_welcome"]}'
# Get attachment
curl http://localhost:4002/gmail/v1/users/me/messages/msg_id/attachments/att_id \
-H "Authorization: Bearer $TOKEN"Upload variants also available at /upload/gmail/v1/users/:userId/messages, .../messages/send, .../messages/import.
Drafts
# List drafts
curl http://localhost:4002/gmail/v1/users/me/drafts \
-H "Authorization: Bearer $TOKEN"
# Create draft
curl -X POST http://localhost:4002/gmail/v1/users/me/drafts \
-H "Authorization: Bearer $TOKEN" \
-H "Content-Type: application/json" \
-d '{"message": {"to": "someone@example.com", "subject": "Draft subject", "body_text": "Draft body"}}'
# Get draft (format: full, metadata, minimal, raw)
curl "http://localhost:4002/gmail/v1/users/me/drafts/draft_id?format=full" \
-H "Authorization: Bearer $TOKEN"
# Update draft
curl -X PUT http://localhost:4002/gmail/v1/users/me/drafts/draft_id \
-H "Authorization: Bearer $TOKEN" \
-H "Content-Type: application/json" \
-d '{"message": {"subject": "Updated subject", "body_text": "Updated body"}}'
# Send draft
curl -X POST http://localhost:4002/gmail/v1/users/me/drafts/send \
-H "Authorization: Bearer $TOKEN" \
-H "Content-Type: application/json" \
-d '{"id": "draft_id"}'
# Delete draft
curl -X DELETE http://localhost:4002/gmail/v1/users/me/drafts/draft_id \
-H "Authorization: Bearer $TOKEN"Threads
# List threads (filter by labels, search query)
curl "http://localhost:4002/gmail/v1/users/me/threads?labelIds=INBOX&maxResults=20" \
-H "Authorization: Bearer $TOKEN"
# Get thread (all messages in thread)
curl "http://localhost:4002/gmail/v1/users/me/threads/thr_welcome?format=full" \
-H "Authorization: Bearer $TOKEN"
# Modify labels on all messages in thread
curl -X POST http://localhost:4002/gmail/v1/users/me/threads/thr_welcome/modify \
-H "Authorization: Bearer $TOKEN" \
-H "Content-Type: application/json" \
-d '{"addLabelIds": ["STARRED"], "removeLabelIds": ["UNREAD"]}'
# Trash / untrash / delete thread
curl -X POST http://localhost:4002/gmail/v1/users/me/threads/thr_welcome/trash \
-H "Authorization: Bearer $TOKEN"
curl -X DELETE http://localhost:4002/gmail/v1/users/me/threads/thr_welcome \
-H "Authorization: Bearer $TOKEN"Labels
# List labels
curl http://localhost:4002/gmail/v1/users/me/labels \
-H "Authorization: Bearer $TOKEN"
# Get label
curl http://localhost:4002/gmail/v1/users/me/labels/INBOX \
-H "Authorization: Bearer $TOKEN"
# Create label
curl -X POST http://localhost:4002/gmail/v1/users/me/labels \
-H "Authorization: Bearer $TOKEN" \
-H "Content-Type: application/json" \
-d '{"name": "My Label", "color": {"backgroundColor": "#DDEEFF", "textColor": "#111111"}}'
# Update label (PUT replaces, PATCH merges)
curl -X PATCH http://localhost:4002/gmail/v1/users/me/labels/Label_ops \
-H "Authorization: Bearer $TOKEN" \
-H "Content-Type: application/json" \
-d '{"name": "Ops/Reviewed"}'
# Delete label (user labels only)
curl -X DELETE http://localhost:4002/gmail/v1/users/me/labels/Label_ops \
-H "Authorization: Bearer $TOKEN"History & Watch
# List history changes since a given historyId
curl "http://localhost:4002/gmail/v1/users/me/history?startHistoryId=1&historyTypes=messageAdded&maxResults=100" \
-H "Authorization: Bearer $TOKEN"
# Set up push notification watch (stub)
curl -X POST http://localhost:4002/gmail/v1/users/me/watch \
-H "Authorization: Bearer $TOKEN" \
-H "Content-Type: application/json" \
-d '{"topicName": "projects/my-project/topics/gmail", "labelIds": ["INBOX"]}'
# Stop watch
curl -X POST http://localhost:4002/gmail/v1/users/me/stop \
-H "Authorization: Bearer $TOKEN"Settings
# List filters
curl http://localhost:4002/gmail/v1/users/me/settings/filters \
-H "Authorization: Bearer $TOKEN"
# Create filter (auto-label incoming messages matching criteria)
curl -X POST http://localhost:4002/gmail/v1/users/me/settings/filters \
-H "Authorization: Bearer $TOKEN" \
-H "Content-Type: application/json" \
-d '{"criteria": {"from": "alerts@example.com"}, "action": {"addLabelIds": ["Label_ops"]}}'
# Delete filter
curl -X DELETE http://localhost:4002/gmail/v1/users/me/settings/filters/filter_id \
-H "Authorization: Bearer $TOKEN"
# List forwarding addresses
curl http://localhost:4002/gmail/v1/users/me/settings/forwardingAddresses \
-H "Authorization: Bearer $TOKEN"
# List send-as aliases
curl http://localhost:4002/gmail/v1/users/me/settings/sendAs \
-H "Authorization: Bearer $TOKEN"Google Calendar API
Calendar List
curl http://localhost:4002/calendar/v3/users/me/calendarList \
-H "Authorization: Bearer $TOKEN"Events
# List events (filter by time range, search, order)
curl "http://localhost:4002/calendar/v3/calendars/primary/events?\
timeMin=2025-01-01T00:00:00Z&timeMax=2025-12-31T23:59:59Z&maxResults=50&orderBy=startTime" \
-H "Authorization: Bearer $TOKEN"
# Create event
curl -X POST http://localhost:4002/calendar/v3/calendars/primary/events \
-H "Authorization: Bearer $TOKEN" \
-H "Content-Type: application/json" \
-d '{"summary": "Team Meeting", "start": {"dateTime": "2025-01-10T14:00:00Z"}, "end": {"dateTime": "2025-01-10T15:00:00Z"}, "attendees": [{"email": "dev@example.com"}]}'
# Delete event
curl -X DELETE http://localhost:4002/calendar/v3/calendars/primary/events/evt_kickoff \
-H "Authorization: Bearer $TOKEN"FreeBusy
curl -X POST http://localhost:4002/calendar/v3/freeBusy \
-H "Authorization: Bearer $TOKEN" \
-H "Content-Type: application/json" \
-d '{"timeMin": "2025-01-10T00:00:00Z", "timeMax": "2025-01-10T23:59:59Z", "items": [{"id": "primary"}]}'Google Drive API
Files
# List files (with query filter, pagination, ordering)
curl "http://localhost:4002/drive/v3/files?q='root'+in+parents&pageSize=20" \
-H "Authorization: Bearer $TOKEN"
# Create file (JSON metadata)
curl -X POST http://localhost:4002/drive/v3/files \
-H "Authorization: Bearer $TOKEN" \
-H "Content-Type: application/json" \
-d '{"name": "notes.txt", "mimeType": "text/plain", "parents": ["root"]}'
# Create file with content (multipart/related upload)
curl -X POST http://localhost:4002/upload/drive/v3/files \
-H "Authorization: Bearer $TOKEN" \
-H "Content-Type: multipart/related; boundary=boundary" \
--data-binary $'--boundary\r\nContent-Type: application/json\r\n\r\n{"name":"data.csv","mimeType":"text/csv"}\r\n--boundary\r\nContent-Type: text/csv\r\n\r\na,b,c\n1,2,3\r\n--boundary--'
# Get file metadata
curl http://localhost:4002/drive/v3/files/drv_readme \
-H "Authorization: Bearer $TOKEN"
# Download file content
curl "http://localhost:4002/drive/v3/files/drv_readme?alt=media" \
-H "Authorization: Bearer $TOKEN"
# Update file (PATCH or PUT; move parents with query params)
curl -X PATCH "http://localhost:4002/drive/v3/files/drv_readme?addParents=folder_id&removeParents=root" \
-H "Authorization: Bearer $TOKEN" \
-H "Content-Type: application/json" \
-d '{"name": "README-updated.md"}'Common Patterns
Full Authorization Code Flow
GOOGLE_URL="http://localhost:4002"
CLIENT_ID="my-client-id.apps.googleusercontent.com"
CLIENT_SECRET="GOCSPX-secret"
REDIRECT_URI="http://localhost:3000/api/auth/callback/google"
# 1. Open in browser (user picks a seeded account)
# $GOOGLE_URL/o/oauth2/v2/auth?client_id=$CLIENT_ID&redirect_uri=$REDIRECT_URI&scope=openid+email+profile&response_type=code&state=abc
# 2. After user selection, emulator redirects to:
# $REDIRECT_URI?code=<code>&state=abc
# 3. Exchange code for tokens
curl -X POST $GOOGLE_URL/oauth2/token \
-H "Content-Type: application/x-www-form-urlencoded" \
-d "code=<code>&client_id=$CLIENT_ID&client_secret=$CLIENT_SECRET&redirect_uri=$REDIRECT_URI&grant_type=authorization_code"
# 4. Fetch user info with the access_token
curl $GOOGLE_URL/oauth2/v2/userinfo \
-H "Authorization: Bearer <access_token>"OIDC Discovery-Based Setup
import { Issuer } from 'openid-client'
const googleIssuer = await Issuer.discover(
process.env.GOOGLE_EMULATOR_URL ?? 'https://accounts.google.com'
)
const client = new googleIssuer.Client({
client_id: process.env.GOOGLE_CLIENT_ID,
client_secret: process.env.GOOGLE_CLIENT_SECRET,
redirect_uris: ['http://localhost:3000/api/auth/callback/google'],
})Send a Gmail Message and Check the Thread
TOKEN="test_token_admin"
BASE="http://localhost:4002"
# Send a message
curl -X POST $BASE/gmail/v1/users/me/messages/send \
-H "Authorization: Bearer $TOKEN" \
-H "Content-Type: application/json" \
-d '{"to": "someone@example.com", "subject": "Test", "body_text": "Hello"}'
# List threads in INBOX
curl "$BASE/gmail/v1/users/me/threads?labelIds=INBOX" \
-H "Authorization: Bearer $TOKEN"