Feature Flags

Legacy documentation. This describes Open Library's old infogami-based feature-flag mechanism. In August 2026, all feature flags were removed in preparation for the FastAPI migration.

The only remaining flag is debug, because it is deeply embedded in infogami and still in use. Do not add new flags to this legacy YAML mechanism. For new feature flags — especially anything in FastAPI land — use pydantic-settings instead.

How debug works

The flag is defined in the features: section of conf/openlibrary.yml:

features:
  debug: enabled

It is checked in Python with infogami's features.is_enabled("debug") (for example, to show debug error pages) and in templates with query_param('debug') (for example, to render the debug stats partial in the site footer when ?debug is present in the URL).