H2 Database Engine is an open source, multiplatform and free graphical software implemented in Java and designed to provide users with a very fast JDBC API that features a browser-based console and leaves a very small footprint (around 1 MB).

The application comes with an embedded mode (in-memory databases), which is faster than the client-server mode. It also features support for encrypted databases, an ODBC (Open Database Connectivity) driver, full-text search, as well as multi version concurrency.

Key features include a very fast database engine, support for standard SQL and JDBC API, clustering support, powerful security options, support for the PostgreSQL ODBC driver, in-memory tables, in-memory databases, disk-based databases, disk-based tables, temporary tables, support for read-only databases, transaction support and table level locking.

The software features 2-phase-commit support, cost-based optimizer, support for multiple connections, support for result sets that are updatable and scrollable, support for external result sorting, support for large result sets, support for AES (Advanced Encryption Standard) encrypted databases, SSL (Secure Socket Layer) support, as well as support for SHA-256 encrypted passwords.

Among other features worth mentioning, we can easily name support for information schema and multiple schemas, collation support, support for roles and users, lossless data compression, outer and inner joins, inline views, read-only views, subqueries, referential integrity, check constraints, autoincrement columns, computed columns and sequence columns.

Currently, H2 Database Engine is fully compatible with the well known MySQL, PostgreSQL, IBM DB2, Apache Derby, Microsoft SQL Server, Oracle and HSQLDB database servers/engines.

Being written in the Java programming language, the H2 Database Engine project is platform-independent and supports any operating system where the Java Runtime Environment (JRE) is available, including GNU/Linux, Microsoft Windows, Mac OS X, Solaris and BSD.