How to get all subscribed topics from firebase cloud messaging

To get information about an app instance ID e.g topics subscribed , platform

const iidToken = "YOUR_IID_TOKEN"; // Replace with your actual Instance ID token
const accessToken = "YOUR_ACCESS_TOKEN" // Replace with the OAuth2 access token

// API endpoint for FCM token info
const url = `https://iid.googleapis.com/iid/info/${iidToken}`;

const headers = {
  Authorization: `Bearer ${accessToken}`,
  'Content-Type': 'application/json',
  // This indicates that OAuth2 authentication is being used
  'access_token_auth': 'true'
};

// Set the optional query parameter to get details (e.g., FCM topic subscription info)
const queryParams = new URLSearchParams({
  details: 'true' // Set to 'true' to get additional details, or omit to get default info
}).toString();

// Make the fetch request to the FCM Instance ID API
fetch(`${url}?${queryParams}`, {
  method: 'GET',
  headers: headers
})
  .then(response => {
    if (!response.ok) {
      throw new Error('Something went wrong');
    }
    return response.json(); // Parse JSON response
  })
  .then(data => {
    console.log('FCM Token Info:', data);
  })
  .catch(error => {
    console.error('Error fetching FCM token info');
  });
copy

Happy coding.