# Extensions

- [Extending Pipelines](/readme/extensions/extending-pipelines.md): Modify system behavior by modifying Pipelines.
- [Order Processing Pipelines](/readme/extensions/extending-pipelines/order-processing-pipelines.md)
- [Checkout Pipelines](/readme/extensions/extending-pipelines/checkout-pipelines.md)
- [Changing Service Behavior](/readme/extensions/change-service-behavior.md)
- [Images](/readme/extensions/change-service-behavior/images.md)
- [Content](/readme/extensions/change-service-behavior/content.md)
- [Extend the Backoffice](/readme/extensions/extend-the-backoffice.md)
- [Custom UI Components](/readme/extensions/extend-the-backoffice/custom-ui-components.md)
- [Custom Editor UI](/readme/extensions/custom-editor-ui.md)
- [Custom Promotion Criteria](/readme/extensions/extending-criteria.md): Promotion criteria in Ucommerce are used to determine when to trigger a discount on an order.
- [Custom Price Group Criteria](/readme/extensions/custom-price-group-criteria.md): Price group criteria in Ucommerce are used to determine the accessibility of a price group.