osTicket

Easy to use but powerful open-source support and ticketing system.

Email-based customer support application, help desk and shared mailbox (alternative to Zendesk and Help Scout).

Marketing, sales, and customer service platform designed to help businesses attract more engaged customers.

Helpdesk software which helps you streamline your company's support, offers an easy setup, clean user interface, and automation tools to resolve customer queries efficiently.

Bug tracker, fits best for software development.

Trudesk is an open-source help desk/ticketing solution.

Real-time error tracking for your applications with all the details in one place. Easy setup with clear instructions included.

Enterprise-grade issue tracking system.

Client IT documentation, ticketing, invoicing and accounting for MSPs (Managed Service Providers).

General-purpose bugtracker and testing tool originally developed and used by the Mozilla project.

Flexible web-based ticketing system used for customer service, help desk, IT service management.