Monorail Issue Tracker

What is Monorail?

Monorail is the issue tracker used by Chromium-related projects on

  • Monorail is a port of the Google Code issue tracker to AppEngine. It provides continuity for the chrome team with the least number of unknowns, while achieving these goals:
    • Vastly simpler to develop and operate:
    • Runs on Google App Engine, data in Google Cloud SQL and GCS.
    • Built on simpler GAE APIs.
    • Pure python, greatly simplified code, supported by Chrome Operations team.
  • Better product focus:
    • Focused on needs of larger teams: e.g., built-in support for user groups, custom fields, more control over issue visibility, better validation to improve issue data quality.
    • Closely aligned with the chrome development process and dedicated to the future needs of the chrome team.
  • Scaleable by design:
    • Designed from the start to handle Chrome's future issue tracking needs.
    • Efficient implementation of queries like issue ID and date ranges.
    • Improved security and spam defenses.
  • Ease of transition:
    • Same data model as used by our existing issues for an exact import.
    • Our v1 API is very close to the old Google Code API.
    • Same ACLs and project administration controls.
    • Familiar UI, but streamlined. One-to-one redirects from Google Code.

Monorail key features

  • Developed as open source.
  • Flexible issue representation that allows for creation of one-off labels.
  • Custom fields defined by project owners.
  • Support for components. Issues can be in multiple components.
  • Filter rules are IF-THEN rules that automatically add labels or CC users.
  • Fine-grained permission system allows control over visiblity and individual actions on individual issues.
  • Saved queries per user and per project.
  • Users can subscribe to their saved queries (not just labels) and get mail on updates.
  • User groups are built into Monorail, so no update lag on built-in groups. We can also sync from Google Groups.
  • Support for custom fields that are treated very much like built-in fields. Custom fields can be multi-valued.
  • User-valued custom fields can be restricted to only allow qualified users that have a given permission.
  • User-valued custom fields can trigger notifications to those users, and/or grant permissions to the named users.
  • Notification emails include detailed footers that give an ordered list of the reasons why the email was sent to you, with specifics such as “You are the on the auto-cc list of Component C”.
  • ML-based spam detection applied before notifications are generated. Users can also flag spam.
  • Limited-availability Endpoints API that works like the old Google Code API.
  • Personal hotlists with ranked issues.

Reporting problems with Monorail

Please file an issue at