When comparing Phabricator vs Bugsnag, the Slant community recommends Phabricator for most people. In the question“What are the best self-hosted bug trackers?” Phabricator is ranked 6th while Bugsnag is ranked 8th. The most important reason people chose Phabricator is:
Phabricator is completely free and open source. It's source code is hosted on [GitHub](https://github.com/phacility/phabricator/).
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Free and open source
Phabricator is completely free and open source. It's source code is hosted on GitHub.
Pro Actively updated
Phabricator is quickly improving, with bug fixes and new features added often. There is an update to the changelog every couple of weeks.
Pro Bug tracker is included
Includes a bug tracker out of the box. Allows for managing bugs, creating issues, commenting on them and closing them.
Pro Supports the three major version control systems
Support for Git, SVN and Mercurial is available.
Pro Super flexible bussiness rules (Herald)
Pro Able to review graphical asset changes as well as code.
Pro Built-in Wiki and pages support
Pro Fine grained access control
With using Spaces and Project and custom policies you can have any combination of access to any object inside of your own Phabricator instance.
Pro Designed by software engineers for software engineers
The engineering workflow is far superior to Github style branching and merging. Phabricator separates local representations of the repository from remote, which enables a variety of workflow optimisations, like stacked diffs on a single branch.
Pro Built-in Q&A platform - Ponder
Instead of having to have separate Q&A tool, there's Ponder which takes out the hassle.
Pro Code ownership
Users can subscribe to files or even repositories and notifications will be sent when code you are subscribed to is changed.
Pro Command Line Access (via arc)
Pro Able to track design mockups
You can track not only code bud also design mockups.
Pro Built-in voting
You can create voting in an instant and need not to rely on external tools.
Pro Built-in blogging platform
There's a great platform which you can use to post stuff, or use as an internal blog, dev blog, release anouncement place and many others.
Pro Built-in Chatrooms
Pro Able to manage legal agreements for open source projects
Pro Fully customizeable workboard
You can configure your workspace to deal with tasks, bugs, todo's, etc.

Pro Great documentation
Clear, concise documentation. Plus docs on cross-domain script errors and enabling CORS.
Pro Email, chat, sms notifications
Bugsnag can be set up to send email notifications as soon as exceptions occur. It can also integrate with a number of third-party services that can be used for notifications including Campfire, HipChat, Twilio SMS and custom solutions via Webhook.
Pro Automatic issues/ticket creation
Bugsnag integrates with a wide variety of 3rd party tools to automatically create issues or tickets. Integrations include GitHub, BitBucket, UserVoice, Trello and many, many others.

Pro Has a free plan
After a two-week full-featured free trial period the user is limited to 2,000 errors/month, 1 user and 1 project.
Pro Exceptions are grouped
Bugsnag groups similar exceptions together displaying the number of occurences so that there's no need to deal with each instance of the error separately.
Pro Exceptional documentation organization
Their documentation was well organized, easy to search through for the platform of choice and quick work of full product integration.
Pro Supports Unity 3D
Drop in place integration with Unity 3D, only a simple API Token configuration on game object and everything was up & running with almost zero code written.
Pro Supports phabricator integrations
Not many products have decided to finally start doing this, phabricator now has a champion.

Pro Source map support

Pro Stack traces
Pro Client libraries are open source

Pro Report uncaught errors
Pro Good web UI
Cons
Con Difficult to configure
Compared to a solution like Bitbucket Server (granted Phabricator offers more options), it is difficult to configure. Settings are scattered everywhere and you must drill down through several screens to find some of them. Documentation is very complete but also not always in parity with the application itself.

Con Blocked by ad blockers by default
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