# Applications

> Applications are the entity where you create and manage your campaigns. Each Application can contain one or more campaigns and API keys to send integration data to Talon.One.

> For the complete documentation index, see [llms.txt](https://docs.talon.one/llms.txt).

You can use Applications, for example, to group your campaigns by country, time zone,
currency, or even by the teams managing your campaigns. You cannot share customer activity
or campaigns across different Applications.

## Application environments

You can create Applications in one of the following environments:

- Sandbox
- Live

They help you differentiate between testing and production Applications. For example,
use a sandbox Application that is connected to a non-production environment on your end
for testing your campaigns extensively or trying out campaign ideas.
When you're satisfied with the results of your testing, copy your successful campaigns
to a live Application that is connected to your production website or app.

With both environments, you can see detailed information about rule failures by including
the `ruleFailureReasons` entity in your request to the
[Update customer profile](/integration-api#tag/Customer-profiles/operation/updateCustomerProfilesV2) and
[Update customer session](/integration-api#tag/Customer-sessions/operation/updateCustomerSessionV2) endpoints.
However, for performance reasons, we recommend you use a sandbox Application
for your testing and debugging.

:::tip
If [campaign staging and revisions][staging-revisions-feature] is enabled,
you can test the rules of campaigns directly in the Application you use for production.
See [Test a campaign][testing-campaigns] and [Revise campaigns][revise-campaign].
:::

:::note
- [Customer profiles](/docs/product/applications/display-customer-profiles.md#customer-profile-environments) created in a
  given environment can only be accessed by Applications from the same
  environment. For example, customer profiles created in a sandbox environment cannot be accessed
  from a live Application.

- [Loyalty programs](/docs/product/loyalty-programs/overview.md#loyalty-program-environments), [audiences](/docs/product/audiences/overview.md#audience-environments)
  and [giveaway pools](/docs/product/giveaways/overview.md#giveaway-pool-environments) from a given environment can only
  be connected to Applications from the same environment.
:::

## Related pages

- [Adding custom attributes to an Application and making
  attributes mandatory](/docs/product/applications/use-attributes)
- [Display customer sessions](/docs/product/applications/display-customer-sessions.md)
- [Manage cart item catalogs](/docs/product/account/dev-tools/manage-cart-item-catalogs.md)

[staging-revisions-feature]: /docs/product/applications/manage-general-settings.md#campaign-staging-and-revisions
[testing-campaigns]: /docs/product/campaigns/create-and-manage-campaigns.md#test-a-campaign
[revise-campaign]: /docs/product/campaigns/revise-campaigns.md