Create a Flag

Creating your first Feature in GrowthBook

A Feature in GrowthBook maps directly to a feature flag in your code. Here is how to create one from scratch.

Step 1 — Open the Features list

Log in to GrowthBook at http://localhost:3000 (or your Cloud URL).
In the left sidebar, click Features.
Click the Add Feature button in the top-right corner.

Step 2 — Fill in the Feature details

Feature Key — enter a lowercase, hyphen-separated identifier, e.g. my-flag. This is the string your code will use forever — choose carefully.
Value Type — select Boolean for a simple on/off flag.
Default Value — set it to false (off by default everywhere).
Click Create Feature.

Step 3 — Enable the flag in an environment

By default, your flag exists but is disabled in all environments.

On the Feature detail page, find the Environments section. You will see rows for development, staging, and production.
Click the toggle next to development to switch it from Disabled to Enabled.
Because there are no override rules, every user will receive the default value of true in development.

Tip: You can set a per-environment default that is different from the global default. This lets you ship true in development while keeping false in production until you are ready.

Reading the flag in your code

Once the feature exists in GrowthBook, use the SDK to evaluate it:

Boolean check with isOn

import { GrowthBook } from '@growthbook/growthbook';

const gb = new GrowthBook({
  apiHost: 'https://cdn.growthbook.io',
  clientKey: 'sdk-YOUR_DEV_KEY',
});

await gb.init({ timeout: 2000 });

if (gb.isOn('my-flag')) {
  console.log('Flag is ON');
} else {
  console.log('Flag is OFF');
}

Reading a value with getFeatureValue

For boolean flags you can also use getFeatureValue, which requires an explicit fallback:

const flagValue = gb.getFeatureValue('my-flag', false);
// returns true or false, never throws

import { GrowthBook } from '@growthbook/growthbook';

const gb = new GrowthBook({
  apiHost: 'https://cdn.growthbook.io',
  clientKey: 'sdk-YOUR_DEV_KEY',
});

await gb.init({ timeout: 2000 });

// boolean shorthand
if (gb.isOn('my-flag')) {
  console.log('Flag is ON');
}

// explicit value with fallback
const flagValue = gb.getFeatureValue('my-flag', false);