Firebase Custom Token API

Create custom tokens for Firebase via API endpoint

Overview

Getting Started
Usage
Built With
Contributing
Deployment

Getting Started

The Firebase Custom Token (FCT) API is a single serverless endpoint that can be used to generate custom tokens for Firebase.

For more information, see Create Custom Tokens from the Firebase docs.

Usage

Authorization

The headers field of every request should include the following keys:

• client_email
• private_key
• project_id

The required keys can be found by generating a private key file from the Firebase Console:

1. Open Settings > Service Accounts
2. Click Generate New Private Key; confirm by clicking Generate Key
3. Securely store the JSON file containing the key

Create Custom Token

Generate a custom token for a single user or batch of users, as well as optionally specify additional claims to be included in each token.

• URL: https://fct-api.flexdevelopment.vercel.app
• Method: POST

Query Parameters

name	type	default	required	description
user_must_exist	boolean	true	false	check if user exists before generating custom token

Request Body

The body of every request should have the following shape:

[
  {
    "uid": 20430108
  }
]

Custom claims can also be specified for each user:

[
  {
    "developerClaims": {
      "admin": true
    },
    "uid": 20430108
  }
]

Sample Response

Default

With developerClaims

With user_must_exist: false

Errors

If an error is thrown, it will have the following shape:

{
  "name": "GeneralError",
  "message": "",
  "code": 500,
  "className": "general-error",
  "data": {
    "body": "",
    "query": {
      "compile": true,
      "options": {}
    }
  },
  "errors": {}
}

404 Sample

{
  "name": "NotFound",
  "message": "There is no user record corresponding to the provided identifier.",
  "code": 404,
  "className": "not-found",
  "data": {
    "codePrefix": "auth",
    "req": {
      "body": [
        {
          "uid": -1
        }
      ],
      "query": {
        "user_must_exist": true
      }
    }
  },
  "errors": {
    "code": "auth/user-not-found",
    "uid": -1
  }
}

Built With

• Firebase Admin - Interact with Firebase from privileged environments
• Vercel - Hosting platform for serverless functions