Creating new flags

Overview

This topic explains how to create new feature flags in LaunchDarkly. You can use feature flags in any aspect of your application, from the customer-facing user interface (UI) to the backend.

The procedures in this topic assume that you have already configured a LaunchDarkly SDK and are ready to use the LaunchDarkly UI.

In the LaunchDarkly UI, you can create a new flag, clone and modify an existing flag to create new ones, and set default values for flags.

Creating a feature flag

You can create and modify feature flags from the flags list. To learn more, read The flags list.

To create a feature flag:

1. Navigate to the flags list.
2. Click Create flag.
3. Enter a unique, human-readable Name.
4. (Optional) Update the flag Key. You'll use this key to reference the flag in your code. A suggested key auto-populates from the name you enter, but you can customize it if you wish.

5. (Optional) Enter a Description of the flag. A brief, human-readable description helps your account members understand what the flag is for. Flag descriptions can include Markdown and inline Confluence links. To learn more about LaunchDarkly's integration with Confluence, read Confluence embedded pages.
6. (Optional) Update the Maintainer for the flag. The maintainer defaults to the flag creator.
7. (Optional) Check the Include flag in this project's release pipeline box. To learn more, read Release pipelines.
8. (Optional) Choose any Metrics to monitor in the Metrics section. To learn more, read Metrics.
9. Choose a flag template in the Configuration section. The options are:

• Custom: A flag that you can configure exactly how you wish.
• Release: A temporary flag that initially serves false to all targets, then progressively rolls out to 100%.
• Kill switch: A permanent flag that enables or disables non-core functionality.
• Experiment: A flag that you can use to test a hypothesis and improve on your findings.
• Migration: A temporary flag used to migrate data or systems while keeping your application available.

10. (Optional) If applicable, follow the instructions for the flag template you chose:

• For a kill switch, experiment, or release flag, select a Flag variations template:
  • Choose whether the flag is temporary or permanent.
  • Boolean: optionally update the Name of the true and false variations.
  • String: enter a Value for each variation, and optionally update the Name of each variation. To add more variations, click +Add variation.
  • Number: enter a Value for each variation, and optionally update the Name of each variation. To add more variations, click +Add variation.
  • JSON: enter a Value for each variation, and optionally update the Name of each variation. To add more variations, click +Add variation.
• For a migration flag, choose a two-, four-, or six-stage migration.

11. (Optional) Update the default variations.
12. (Optional) Choose one or more tags from the Tags menu.

13. Check the SDKs using Mobile Key and/or SDKs using client-side ID boxes to indicate which client-side SDKs you will use to evaluate this flag. If you are using a server-side SDK, leave these boxes unchecked.
14. Click Create flag.

The new flag appears in the flags list.

Making flags available to client-side and mobile SDKs

By default, flags are only available to server-side SDKs. When you create a flag, you can choose to expose the flag to SDKs which use client-side IDs, SDKs which use mobile keys, or both. If you're using a client-side or mobile SDK, you must expose your feature flags in order for the client-side or mobile SDKs to evaluate them.

Here is an image of the "Client-side SDK availability" section on a flag's Settings tab:

If an SDK tries to evaluate a feature flag that is not available, LaunchDarkly serves the default value for that flag.

To make all of a project's flags available to client-side or mobile SDKs by default, check the SDKs using Client-side ID or SDKs using Mobile key checkboxes in the project's Flags tab.

To learn more, read Client-side, server-side, and edge SDKs.

Configuring the same flag in different environments

All environments within a project have the same set of feature flags. When you create a new feature flag, it is created in every environment in your LaunchDarkly project. That flag is scoped to your entire project.

Flag configuration settings are specific to each environment. The changes you make in one environment do not apply to the same flag in any other environment. If you want to, you can configure the same flag in a unique way for every environment you have.

To configure a flag in a different environment:

1. Navigate to the flags list.
2. Click the environment name in the top left corner. The "Switch environment" menu appears:

3. Search for the environment you wish to switch to and click on it, or choose it from the list. The flags list for the new environment appears.

4. Find the flag you wish to modify and make whatever changes you like.

Setting default values

When you create a feature flag, some of its variations are designated as default values. You can accept the defaults or change them. When you change default values for a new flag, LaunchDarkly creates the flag across all environments in your project with the new variations set as its default on and off values.

To learn more about default flag values, read Changing default flag values.

Cloning flags

You can create new flags by cloning existing flags. When you clone a flag, LaunchDarkly makes a new flag and copies the original flag's targeting configuration for all environments, including default values and whether the flag is toggled on or off. You can then modify the clone's configuration if needed.

To clone a flag:

1. Navigate to the flags list.
2. Find the flag you wish to clone and click its name. The flag's Targeting tab appears.
3. Click the flag's Settings tab.
4. In the "Clone flag" section, click Clone this flag.
5. The "Clone feature flag" dialog appears:

6. Enter a unique, human-readable Name.
7. Enter a unique flag Key. You'll use this key to reference the flag in your code. A suggested key auto-populates from the name you enter, but you can customize it if you wish.
8. (Optional) Enter a Description of the new flag. A brief, human-readable description helps your account members understand what the flag is for.
9. (Optional) Click into the Tags menu and choose one or more tags for your flag.

10. Click Save flag. You are taken to the new flag's details page.

The new flag appears in the flags list.