Flask 0.9 changelog →

Lots of great stuff. The JSON stuff is moving in the right direction.

My two favorites:

:meth:~flask.Flask.get_send_file_max_age hook for subclasses to override behavior of serving static files from Flask when using :meth:flask.Flask.send_static_file (used for the default static file handler) and :func:~flask.helpers.send_file. This hook is provided a filename, which for example allows changing cache controls by file extension. The default max-age for send_file and static files can be configured through a new SEND_FILE_MAX_AGE_DEFAULT configuration variable, which is used in the default get_send_file_max_age implementation.

and

Added :func:flask.after_this_request.