# Extension functions

- [Core functions](/xforms/xpath/extension-functions/core-functions.md)
- [Utility functions](/xforms/xpath/extension-functions/utility-functions.md)
- [Model functions](/xforms/xpath/extension-functions/model-functions.md)
- [Validation functions](/xforms/xpath/extension-functions/validation-functions.md)
- [Controls functions](/xforms/xpath/extension-functions/controls-functions.md)
- [XML functions](/xforms/xpath/extension-functions/xml-functions.md)
- [JSON functions](/xforms/xpath/extension-functions/json-functions.md)
- [HTTP functions](/xforms/xpath/extension-functions/http-functions.md)
- [Form Runner functions](/xforms/xpath/extension-functions/form-runner-functions.md)
- [Other functions](/xforms/xpath/extension-functions/other-functions.md)
- [Deprecated functions](/xforms/xpath/extension-functions/deprecated-functions.md)