IBM DevOps Code ClearCase (also known as IBM Rational ClearCase) is a family of computer software tools that supports software configuration management (SCM) of source code and other software development assets. It also supports design-data management of electronic design artifacts, thus enabling hardware and software co-development. ClearCase includes revision control and forms the basis for configuration management at large and medium-sized businesses, accommodating projects with hundreds or thousands of developers. It is developed by IBM.

ClearCase supports two configuration management models: UCM (Unified Change Management) and base ClearCase. UCM provides an out-of-the-box model while base ClearCase provides a basic infrastructure (UCM is built on base ClearCase). Both can be customized to support a wide variety of needs.

ClearCase can accommodate large binary files, a large number of files, and large repository sizes. It supports branching and labeling. It enables the correct merging of refactored files by versioning directories. It also supports extensive process automation and enforcement using triggers, attributes, hyperlinks, and other metadata. It uses the MultiVersion File System (MVFS), which is a virtual file system that transparently determines which versions of files and directories should be in the workspace and orchestrates file access and lifecycle. The MVFS is used in LAN deployments for dynamic views and in LAN or WAN deployments for automatic views.

ClearCase also provides authoritative build auditing, which generates metadata for each build artifact, including the context of the build and a bill of materials of files (including the exact version) referenced during the build. This metadata can be used for generating SBOMs (Software Bill of Materials) and is important in regulated environments where artifact traceability is essential. ClearCase includes an implementation of 'make' that integrates with the authoritative build auditing mechanism to ensure build correctness without timestamps and automatic sharing of build artifacts across views (workspaces).

ClearCase was developed by Atria Software and first released in 1992 on Unix and later on Windows. Some of the Atria developers had worked on an earlier, similar system: DSEE (Domain Software Engineering Environment) from Apollo Computer. After Hewlett-Packard bought Apollo Computer in 1989, those developers left to form Atria. Atria later merged with Pure Software to form PureAtria in 1996. That firm was acquired by Rational Software in 1997, which was purchased by IBM in 2003. IBM continues to develop and market ClearCase. In September 2016, IBM announced a strategic partnership with HCL Technologies that will allow for accelerated development.

The database system that ClearCase uses is RDM Embedded from Raima. In ClearCase terminology, an individual database is called a VOB (Versioned Object Base). On this layer, maintenance takes place using Raima tooling. Around this layer, a set of interfaces with accompanying tools are used to manage the physical database system, which requires specific Database administrator skills.

The most important service is the Atria location Broker Daemon (ALBD), which manages all (LAN) communication between computers. Beginning with version 7, the server platform runs Websphere Application Server with a server application called the Change Management Server (CM Server), which served ClearCase clients via the HTTP Protocol. (Before version 7 there was a web service by which users could access ClearCase via their browsers.) CM server has since been replaced by the ClearCase Remote Client Wide-Area Network Server (CCRC WAN server), which continues to be based on Websphere Application Server.

A distinguishing feature of ClearCase is the MultiVersion File System (MVFS), a proprietary networked filesystem which can mount VOBs as a virtual file system through a dynamic view, selecting a consistent set of versions and enabling the production of derived objects. This was a departure from the repository-and-sandbox model because it enabled the early management of artifacts (that is, before they are checked in) and was not limited to the management of these first-order configuration items.