Firebase Remote Config — Feature Flags, A/B Testing, and Dynamic App Configuration

// Web: Fetch and use Remote Config
import { getRemoteConfig, getValue, fetchAndActivate } from 'firebase/remote-config';

const remoteConfig = getRemoteConfig();
remoteConfig.settings.minimumFetchIntervalMillis = 3600000; // 1 hour

async function initializeConfig() {
  await fetchAndActivate(remoteConfig);

  // Get feature flag
  const newDashboard = getValue(remoteConfig, 'new_dashboard_enabled');
  if (newDashboard.asBoolean()) {
    renderNewDashboard();
  } else {
    renderLegacyDashboard();
  }

  // Get string parameter
  const apiEndpoint = getValue(remoteConfig, 'api_endpoint');
  config.apiUrl = apiEndpoint.asString();

  // Get number parameter
  const maxItems = getValue(remoteConfig, 'max_items_per_page');
  config.pageSize = maxItems.asNumber();
}

// Remote Config with React
import { useEffect, useState } from 'react';
import { getRemoteConfig, getValue, fetchAndActivate } from 'firebase/remote-config';

function useFeatureFlag(flagName) {
  const [enabled, setEnabled] = useState(false);

  useEffect(() => {
    async function load() {
      const rc = getRemoteConfig();
      await fetchAndActivate(rc);
      const value = getValue(rc, flagName);
      setEnabled(value.asBoolean());
    }
    load();
  }, [flagName]);

  return enabled;
}

function App() {
  const isNewUIEnabled = useFeatureFlag('new_ui_enabled');
  const welcomeMessage = useFeatureFlag('welcome_message');

  return (
    <div>
      {isNewUIEnabled ? <NewUI /> : <LegacyUI />}
      <h1>{welcomeMessage}</h1>
    </div>
  );
}

# Admin SDK: Set Remote Config parameters
import firebase_admin
from firebase_admin import remote_config

template = remote_config.get_template()

# Add feature flag
new_feature = remote_config.Parameter()
new_feature.default_value = remote_config.ParameterValue(
    value='false'
)

# Add condition-based value
ios_condition = remote_config.Condition(
    name='isIOS',
    expression='device.os == "ios"'
)

new_feature.conditional_values = [
    remote_config.ConditionalValue(
        condition_name='isIOS',
        value=remote_config.ParameterValue(value='true')
    )
]

template.parameters['new_feature_enabled'] = new_feature
template.conditions = [ios_condition]

# Publish
template = remote_config.publish_template(template)
print('Remote Config published')

# Manage Remote Config via CLI
firebase remoteconfig:get --template > config.json

# Edit config.json, then publish
firebase remoteconfig:deploy config.json

# Rollback to previous version
firebase remoteconfig:rollback --version=5