All classes that implement PlaceholderStrategyInterface in Drupal 8
- class \Drupal\Core\Render\Placeholder\ChainedPlaceholderStrategy implements PlaceholderStrategyInterface
- class \Drupal\Core\Render\Placeholder\SingleFlushStrategy implements PlaceholderStrategyInterface
- class \Drupal\big_pipe\Render\Placeholder\BigPipeStrategy implements PlaceholderStrategyInterface
- class \Drupal\big_pipe_sessionless\Render\Placeholder\BigPipeSessionlessStrategy