Google Cloud & config files

Everything you need in Google Cloud / Firebase before testing sign-in. Applies to bare React Native and Expo.

Labels used in this guide:

Label	Meaning
Required	Needed for sign-in to work in production-like builds
Required for `autoDetect`	Only when `webClientId: 'autoDetect'`
Optional	Skip unless noted; use when you want convenience or a specific setup path

Quick checklist

Step		Why
Google Cloud / Firebase project	Required	OAuth clients and config files live in a Google project
OAuth consent screen	Required	Google blocks sign-in for production/testing users without it
Web + Android + iOS OAuth clients	Required	Each platform validates package/bundle and issues tokens
Android SHA-1 fingerprints	Required (Android)	Google matches your signing certificate; missing SHA-1 → `DEVELOPER_ERROR`
iOS URL scheme (`REVERSED_CLIENT_ID`)	Required (iOS)	OAuth redirect must return to your app
`google-services.json` + Android Gradle plugin	Required for `autoDetect`	Generates `default_web_client_id` on Android
`GoogleService-Info.plist`	Required for `autoDetect` on iOS	Supplies `WEB_CLIENT_ID`; also easiest source for URL scheme
Firebase download path	Optional	Alternative to manual OAuth setup; same files
Explicit `webClientId` in JS	Optional	Skips Android JSON + Gradle; you still need SHA-1 (Android) and URL scheme (iOS)
`androidx.credentials` in your app Gradle	Optional (omit)	Shipped by the library — Android Credential Manager & GMS

// Required for autoDetect on both platforms:
GoogleOneTapSignIn.configure({ webClientId: 'autoDetect' })

// Optional path — no google-services.json on Android:
GoogleOneTapSignIn.configure({
  webClientId: 'YOUR_WEB_CLIENT_ID.apps.googleusercontent.com',
})

Config files are gitignored in this repo — use your own project.

1. Create a Google Cloud project

Required

Why: OAuth client IDs, consent screen, and (via Firebase) google-services.json / GoogleService-Info.plist are all tied to a Google Cloud project. Without a project you cannot register your app with Google.

Open Google Cloud Console or Firebase Console (linked to the same Cloud project).
Create or select a project.

Required

Why: Google shows the consent screen to users. An incomplete or missing consent configuration blocks sign-in or limits which Google accounts can authenticate.

Configure the OAuth consent screen (app name, support email, scopes).

3. Create OAuth clients

Required

Why: Each platform uses a different client type. The Web client ID is what you pass as webClientId (or embed in config files for autoDetect). Android and iOS clients tie Google to your package name / bundle ID and certificates.

In APIs & Services → Credentials, create:

Type	Used for
Web application	`webClientId`; backend ID token verification
Android	Package name + SHA-1
iOS	Bundle ID; `REVERSED_CLIENT_ID` for URL scheme

Web client ID

Optional if you only use autoDetect

Why optional: With autoDetect, the Web client ID can come from google-services.json / plist. You still need a Web OAuth client in the same project for token validation on your backend.

Copy the Web client ID (ends with .apps.googleusercontent.com) if you configure manually.

Android OAuth client (Google Cloud)

Create an Android OAuth client in Google Cloud Console

iOS OAuth client (Google Cloud)

Create an iOS OAuth client and download plist from Google Cloud

4. Android SHA-1

Required on Android

Why: Google Sign-In checks that the app requesting tokens is signed with a certificate you registered. Wrong or missing SHA-1 causes DEVELOPER_ERROR even when everything else is correct.

Get your debug keystore SHA-1:

keytool -list -v \
  -keystore ~/.android/debug.keystore \
  -alias androiddebugkey \
  -storepass android -keypass android

Bare RN project keystore:

keytool -list -v \
  -keystore android/app/debug.keystore \
  -alias androiddebugkey \
  -storepass android -keypass android

Register the fingerprint in Google Cloud (Android OAuth client) and/or Firebase (Project settings → Android app).

Add SHA-1 fingerprint on the Android OAuth client in Google Cloud Console

Required for release

Why: Play Store builds use different certificates. Add release and Play App Signing SHA-1 values before shipping production.

5. Download config files

`google-services.json` (Android)

Required for autoDetect on Android

Why: The Google Services Gradle plugin reads this file and generates the default_web_client_id string resource. Native code reads that resource when webClientId is 'autoDetect'.

Optional with explicit webClientId

Why optional: If you pass the Web client ID string in configure(), Android does not need this file — but SHA-1 is still required.

Download google-services.json from Firebase

`GoogleService-Info.plist` (iOS)

Required for autoDetect on iOS

Why: Native code reads WEB_CLIENT_ID from the plist when using autoDetect. Firebase-generated plists include it.

Optional for explicit webClientId only

Why optional for client ID: You can pass webClientId in JS instead. You still need the iOS URL scheme (see iOS setup) — the plist is the easiest way to get REVERSED_CLIENT_ID.

Download GoogleService-Info.plist from Firebase

From Firebase (recommended path)

Optional path (recommended)

Why use it: One console for Android + iOS apps, SHA-1 management, and downloading both files with matching OAuth metadata.

Firebase Console → your project.
Add app → Android — package = your applicationId → download google-services.json
Add app → iOS — bundle ID = your bundleIdentifier → download GoogleService-Info.plist
Add SHA-1 (§4); re-download JSON if Firebase prompts.

File	Platform	Provides
`google-services.json`	Android	`default_web_client_id` + Gradle integration
`GoogleService-Info.plist`	iOS	`WEB_CLIENT_ID`, `REVERSED_CLIENT_ID`

6. Where to put the files

Required when using those files

Why: Build tools only read config from known paths. Wrong location = missing resources at runtime.

Environment	`google-services.json`	`GoogleService-Info.plist`
Bare React Native	`android/app/google-services.json`	Xcode app target
Expo	Path in `app.config` (e.g. `./google-services.json`)	e.g. `./GoogleService-Info.plist`
Repo `example/`	`example/android/app/`	iOS Xcode target
Repo `example-expo/`	`example-expo/`	`example-expo/`

Bare React Native

Step		Why
Copy `google-services.json` → `android/app/`	Required for `autoDetect`	Gradle plugin input location
Gradle plugin	Required for `autoDetect`	Processes JSON into `default_web_client_id`
Plist in Xcode + URL scheme	Required (iOS)	Redirect + `autoDetect` on iOS
AppDelegate `handle(url)`	Optional (recommended bare RN)	Forwards OAuth redirect to `GIDSignIn`

Expo

Step		Why
`googleServicesFile` in `app.config`	Required for `autoDetect`	Plugin copies files at prebuild
`expo prebuild`	Required after native config changes	Applies plugin + Gradle
Manual Gradle edits	Optional	Config plugin applies Gradle for you
AppDelegate patch after prebuild	Optional	Only if sign-in stalls or you have other URL handlers

plugins: ['react-native-nitro-google-signin'],
android: { googleServicesFile: './google-services.json' },
ios: { googleServicesFile: './GoogleService-Info.plist' },

7. Verify config files

Optional but recommended

Why: Catches package name / bundle ID mismatches before long native rebuild cycles.

google-services.json — package_name matches applicationId
GoogleService-Info.plist — contains REVERSED_CLIENT_ID; WEB_CLIENT_ID for autoDetect

8. Sample apps in this repo

Optional

Why: Only needed if you run the bundled examples. Use package/bundle com.nitrogooglesigninexample or change app configs to match your files.

App	Config file locations
`example/`	`example/android/app/` + iOS Xcode
`example-expo/`	`example-expo/`

9. Link OAuth clients

Required for backend token verification

Why: ID tokens from Android/iOS must correspond to the same Google project as your Web client so your server can verify them with Google's public keys.

Ensure Web, Android, and iOS clients live in the same Google Cloud project.

See also Android setup and iOS setup for platform-specific config file steps.

Troubleshooting

Issue	Fix
`default_web_client_id was not found`	JSON + Gradle plugin + matching package name
`DEVELOPER_ERROR` (Android)	SHA-1 / package name
iOS redirect errors	URL scheme = `REVERSED_CLIENT_ID`
Expo changes ignored	`expo prebuild --clean` + rebuild dev client

Android · iOS · Expo · Troubleshooting.

Quick checklist​

1. Create a Google Cloud project​

2. OAuth consent screen​

3. Create OAuth clients​

Web client ID​

Android OAuth client (Google Cloud)​

iOS OAuth client (Google Cloud)​

4. Android SHA-1​

5. Download config files​

google-services.json (Android)​

GoogleService-Info.plist (iOS)​

From Firebase (recommended path)​

6. Where to put the files​

Bare React Native​

Expo​

7. Verify config files​

8. Sample apps in this repo​

9. Link OAuth clients​

Troubleshooting​

Quick checklist

1. Create a Google Cloud project

2. OAuth consent screen

3. Create OAuth clients

Web client ID

Android OAuth client (Google Cloud)

iOS OAuth client (Google Cloud)

4. Android SHA-1

5. Download config files

`google-services.json` (Android)

`GoogleService-Info.plist` (iOS)

From Firebase (recommended path)

6. Where to put the files

Bare React Native

Expo

7. Verify config files

8. Sample apps in this repo

9. Link OAuth clients

Troubleshooting