| ExtensionInterface | Interface implemented by extension classes. |
| GlobalsInterface | Enables usage of the deprecated Twig_Extension::getGlobals() method. |
| InitRuntimeInterface | Enables usage of the deprecated Twig_Extension::initRuntime() method. |
| RuntimeExtensionInterface |
| AbstractExtension | |
| CoreExtension | |
| DebugExtension | |
| EscaperExtension | |
| OptimizerExtension | |
| ProfilerExtension | |
| SandboxExtension | |
| StagingExtension | Used by Twig_Environment as a staging area. |
| StringLoaderExtension |
