GitLab can be integrated with external services for enhanced functionality.
## Issue trackers
You can use an [external issue tracker](external-issue-tracker.md) at the same time as the GitLab issue tracker, or use only the external issue tracker.
GitLab can be integrated with the following external issue trackers:
- Jira
- Redmine
- Bugzilla
- YouTrack
## Authentication sources
GitLab can be configured to authenticate access requests with the following authentication sources:
- Enable the [Auth0 OmniAuth](auth0.md) provider.
- Enable sign in with [Bitbucket](bitbucket.md) accounts.
- Configure GitLab to sign in using [CAS](cas.md).
- Configure GitLab as a [SAML](saml.md) 2.0 Service Provider.
## Security enhancements
GitLab can be integrated with the following external services to enhance security:
- [Akismet](akismet.md) helps reduce spam.
- Google [reCAPTCHA](recaptcha.md) helps verify new users.
GitLab also provides features to improve the security of your own application. For more details see [GitLab Secure](../user/application_security/index.md).
## Continuous integration
GitLab can be integrated with the following external service for continuous integration:
- [Jenkins](jenkins.md) CI. **(STARTER)**
## Feature enhancements
GitLab can be integrated with the following enhancements:
- Add GitLab actions to [Gmail actions buttons](gmail_action_buttons_for_gitlab.md).
- Configure [PlantUML](../administration/integration/plantuml.md) to use diagrams in AsciiDoc documents.
- Attach merge requests to [Trello](trello_power_up.md) cards.
- Enable integrated code intelligence powered by [Sourcegraph](sourcegraph.md).
Integration with services such as Campfire, Flowdock, HipChat, Pivotal Tracker, and Slack are available as [Integrations](../user/project/integrations/overview.md).
When trying to integrate GitLab with services that are using self-signed certificates, it is very likely that SSL certificate errors will occur in different parts of the application, most likely Sidekiq.
This [resource](https://manuals.gfi.com/en/kerio/connect/content/server-configuration/ssl-certificates/adding-trusted-root-certificates-to-the-server-1605.html)
[Install the self signed certificate or custom certificate authorities](https://docs.gitlab.com/omnibus/common_installation_problems/README.html#using-self-signed-certificate-or-custom-certificate-authorities)