Mono (software)

Mono project logo.svg
Diagram of Mono architecture
Diagram of Mono architecture
Original author(s)Ximian
Developer(s).NET Foundation and Xamarin (a Microsoft subsidiary)
Initial releaseJune 30, 2004; 15 years ago (2004-06-30)
Stable release / July 17, 2019; 2 months ago (2019-07-17)[1]
Preview release / August 28, 2019; 46 days ago (2019-08-28)[2] Edit this at Wikidata
Written inC, C#, XML
Operating systemWindows, macOS, Linux
PlatformIA-32, x64, IA-64, ARM, MIPS, PowerPC, SPARC, S390
TypeSoftware framework
LicenseMIT License[3]

Mono is a free and open-source project to create an Ecma standard-compliant .NET Framework-compatible software framework, including a C# compiler and a Common Language Runtime. Originally by Ximian, it was later acquired by Novell, and is now being led by Xamarin, a subsidiary of Microsoft[4] and the .NET Foundation. The stated purpose of Mono is not only to be able to run Microsoft .NET applications cross-platform, but also to bring better development tools to Linux developers.[5] Mono can be run on many software systems including Android, most Linux distributions, BSD, macOS, Windows, Solaris, and even some game consoles such as PlayStation 3, Wii, and Xbox 360.

The Mono project has been controversial within the open-source community, as it implements portions of .NET Framework that may be covered by Microsoft patents. Although standardized portions of .NET Framework are covered under Microsoft Open Specification Promise—a covenant stating that Microsoft will not assert its patents against implementations of its specifications under certain conditions—other portions are not, which led to concerns that the Mono project could become the target of patent infringement lawsuits. Following Microsoft's open-sourcing of several core .NET technologies since 2014 and its acquisition of Xamarin in the beginning of 2016, an updated patent promise has been issued for the Mono project (§ Mono and Microsoft's patents).

The logo of Mono is a stylized monkey's face, mono being Spanish for monkey.[6]


Release History[7]
Date Version[8] Notes
2004-06-30 1.0[9] C# 1.0 support
2004-09-21 1.1[10]
2006-11-09 1.2[11] C# 2.0 support
2008-10-06 2.0[12] Mono's APIs are now in par with .NET 2.0. Introduces the C# 3.0 and Visual Basic 8 compilers. New Mono-specific APIs: Mono.Cecil, Mono.Cairo and Mono.Posix. Gtk# 2.12 is released. The Gendarme verification tool and Mono Linker are introduced.
2009-01-13 2.2[13] Mono switches its JIT engine to a new internal representation[14] that gives it a performance boost and introduces SIMD support in the Mono.Simd[15] Mono.Simd namespace.
Mono introduces Full Ahead of Time compilation that allows developers to create full static applications and debuts the C# Compiler as a Service[16] and the C# Interactive Shell[17] (C# REPL)
2009-03-30 2.4[18] This release mostly polishes all the features that shipped in 2.2 and became the foundation for the Long-Term support of Mono in SUSE Linux.
2009-12-15 2.6[19] The Mono runtime is now able to use LLVM as a code generation backend and this release introduces Mono co-routines, the Mono Soft Debugger and the CoreCLR security system required for Moonlight and other Web-based plugins.
On the class library System.IO.Packaging, WCF client, WCF server, LINQ to SQL debut. The Interactive shell supports auto-completion and the LINQ to SQL supports multiple database backends. The xbuild build system is introduced.
2010-09-22 2.8[20] Defaults to .NET 4.0 profile, C# 4.0 support, new generational garbage collector, includes Parallel Extensions, WCF Routing, CodeContracts, ASP.NET 4.0, drops the 1.0 profile support; the LLVM engine tuned to support 99.9% of all generated code, runtime selectable llvm and gc; incorporates Dynamic Language Runtime, MEF, ASP.NET MVC2, OData Client open-source code from Microsoft;. Will become release 3.0
2011-02-15 2.10[21]
2012-10-18 3.0[22] C# 5.0 support, async support, Async Base Class Library Upgrade and MVC4 - Partial, no async features support.
2013-07-24 3.2[23] Default Garbage Collector is now the SGEN, instead of Boehm
2014-03-31 3.4[24]
2014-08-12 3.6[25]
2014-09-04 3.8[26]
2014-10-04 3.10[27]
2015-01-13 3.12[28]
2015-04-29 4.0[29] Defaults to .NET 4.5 profile and ships only .NET 4.5 assemblies, defaults to C# 6.0. First release to integrate Microsoft open-source .NET Core code
2017-05-10 5.0[30] Shipping Roslyn C# compiler to enable C#7 support; Shipping msbuild and deprecating xbuild for better compatibility; Enabling concurrent SGen garbage collector to reduce time spent in GC; Introducing the AppleTLS stack on macOS for HTTPS connections; Continued Progress on .NET Class Library convergence; Updated libjpeg in macOS package
2017-07-14 5.2[31] Support for .NET Standard 2.0, strong assembly names, and experimental default interface members.
2017-10-05 5.4[32] The JIT Runtime now supports concurrent method compilation and various other Performance Optimisations;
2018-02-01 5.8[33] Initial WebAssembly port; Modes for the SGen GC; Includes Roslyn’s csi (C# interactive) REPL tool
2018-02-26 5.10[34] The Interpreter is now included in the default installation; runtime now supports Default Interface Methods; WebAssembly considered reliable now; Support for .NET 4.7.1 / C# 7.2 / F# 4.1
2018-05-08 5.12[35] Port to IBM AIX/i; now includes VB.NET compiler; option to use jemalloc
2018-08-07 5.14[36] Major Windows.Forms update to improve compatibility with .NET
2018-10-08 5.16[37] Hybrid suspend garbage collector; Client certificate support; C# 7.3 support
2018-12-21 5.18[38] .NET 4.7.2 support; more CoreFX code is used
2019-07-17 6.0.0 C# compiler defaults to version C# 8.0 RC; Various stability improvement in debugger support; Mono Interpreter is feature complete and stable

When Microsoft first announced their .NET Framework in June 2000 it was described as "a new platform based on Internet standards",[39] and in December of that year the underlying Common Language Infrastructure was published as an open standard, "ECMA-335",[40] opening up the potential for independent implementations.[41] Miguel de Icaza of Ximian believed that .NET had the potential to increase programmer productivity and began investigating whether a Linux version was feasible.[42] Recognizing that their small team could not expect to build and support a full product, they launched the Mono open-source project, on July 19, 2001 at the O'Reilly conference.

After three years' development, Mono 1.0 was released on June 30, 2004.[43] Mono evolved from its initial focus of a developer platform for Linux desktop applications to supporting a wide range of architectures and operating systems - including embedded systems.[44]

Novell acquired Ximian in 2003. After Novell was acquired by Attachmate in April 2011, Attachmate announced hundreds of layoffs for the Novell workforce,[45] putting in question the future of Mono.[46][47]

On May 16, Miguel de Icaza announced in his blog that Mono would continue to be supported by Xamarin, a company he founded after being laid off from Novell. The original Mono team had also moved to the new company. Xamarin planned to keep working on Mono and had planned to rewrite the proprietary .NET stacks for iOS and Android from scratch, because Novell still owned MonoTouch and Mono for Android at the time.[48] After this announcement, the future of the project was questioned, MonoTouch and Mono for Android being in direct competition with the existing commercial offerings now owned by Attachmate, and considering that the Xamarin team would have difficulties proving that they did not use technologies they formerly developed when they were employed by Novell for the same work.[49] However, in July 2011, Novell, now a subsidiary of Attachmate, and Xamarin, announced that it granted a perpetual license to Xamarin for Mono, MonoTouch and Mono for Android, which officially took stewardship of the project.[50][51]