What’s new in Tornado 6.4.0

Nov 28, 2023

General Changes

  • Python 3.12 is now supported. Older versions of Tornado will work on Python 3.12 but may log deprecation warnings.

Deprecation Notices


  • The client_secret argument to OAuth2Mixin.authorize_redirect is deprecated and will be removed in Tornado 7.0. This argument has never been used and other similar methods in this module don’t have it.

  • TwitterMixin is deprecated and will be removed in the future.


  • Autoreload can now be used when the program is run as a directory rather than a file or module.

  • New CLI flag --until-success re-runs the program on any failure but stops after the first successful run.


  • Fixed reference cycles that could lead to increased memory usage.


  • Several methods in this module now simply pass through to their equivalents in the standard library.


  • This module now holds a strong reference to all running asyncio.Task objects it creates. This prevents premature garbage collection which could cause warnings like “Task was destroyed but it is pending!”.






  • Unclosed client connections now reliably log a warning. Previously the warning was dependent on garbage collection and whether the ping_interval option was used.

  • The subprotocols argument to WebSocketClientConnection now defaults to None instead of an empty list (which was mutable and reused)