[2][3] Icinga tries to improve Nagios' development process[4] as well as adding new features[5][6] such as a modern Web 2.0 style user interface, additional database connectors (for MySQL, Oracle, and PostgreSQL), and a REST API that lets administrators integrate numerous extensions without complicated modification of the Icinga core.

[10] In their first year, Icinga developers released separate versions of Core, API, and Web, and celebrated their 10,000th download.

[11] In its second year, the Icinga project released unified and stable Core and Web; added dual-stack IPv6 and IPv4 support, optimized database connectivity, and revamped the Icinga Web user interface, integrating various community add-ons (PNP4Nagios, LConf, Heatmap and Business Process Addon).

Due to its nature as a fork, Icinga offers Nagios’ features with some additions such as optional reporting module with improved SLA accuracy, additional database connectors for PostgreSQL and Oracle, and distributed systems for redundant monitoring.

Icinga also maintains configuration and plug-in compatibility with Nagios,[11] facilitating migration between the two monitoring software.

The latter communicates via Icinga's Doctrine abstraction layer, REST and plug-in APIs that mediate between the external data and internal structures.

[18] The Icinga Core manages monitoring tasks, receiving check results from various plug-ins.

Icinga 2 manages monitoring tasks, running checks, and sending alert notifications.

Icinga 2 ships a built-in cluster stack secured by SSL x509 certificates attempting to make distributed monitoring setups more easy.

In contrast to its predecessor Nagios, Icinga supports PostgreSQL and Oracle databases in addition to MySQL.

It allows for monitoring resources such as disk usage, system load or the number of users currently logged in.