> ## Documentation Index
> Fetch the complete documentation index at: https://launchdarkly.com/docs/llms.txt
> Use this file to discover all available pages before exploring further.
# Custom properties
This topic explains how to set up and use custom properties in LaunchDarkly.
If you're building an integration for LaunchDarkly, it might be helpful to store data for your integration with a LaunchDarkly feature flag. Custom properties allow you to do this.
Each custom property you add to a feature flag can contain a list of associated values. For example, if you create an integration with an issue tracking service, you may want to associate a flag with a list of issues related to a feature's development.
## Create a custom property type
Before you create a custom property type, you must first choose the flag you plan to add it to.
To create a custom property type:
1. In the left sidebar, click **Code**. The CodeControl menu appears.
2. Click **Flags**.
3. Open the flag you wish to deprecate.
4. Click the **three-dot** overflow menu in the right sidebar.
5. Select **Add custom property**.
6. Enter the new property type name in the **Type** field.
7. (Optional) Edit the **Key** if needed.
8. Enter the **Values** associated with the custom property.
9. Click **Save**.
After you create a custom property, it appears in the right sidebar, under the "Links" section.
## Add a custom property
To add an existing custom property to a flag:
1. In the left sidebar, click **Code**. The CodeControl menu appears.
2. Click **Flags**.
3. Open the flag you wish to add a custom property to.
4. Click the **three-dot** overflow menu in the right sidebar.
5. Select **Add custom property**.
6. Select a property **Type** from the menu.
7. Enter the **Values** associated with the property.
8. Click **Save**.
You can also use the REST API: [Create a feature flag](/docs/api/feature-flags/create-a-feature-flag)
**Custom property restrictions**
Custom properties have the following restrictions:
* You can set a maximum of 64 custom properties
* Each custom property's name and key must be at most 64 characters