Developer Documentation

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Source Code Repository Access

OpenSimulator uses git as its source code repository. Checkout

git clone git://

See Source Code Repository for more details.

See Using Git for more Details on installing and using GIT with

You can also browse the source code for OpenSimulator using a web browser.

We have Ohloh page, which takes various statistics of the OpenSimulator code base.

This is also an opensim-libs git repository which contains the source code to some of the 3rd party libraries built and included in OpenSimulator.


Submitting Patches

Please review Submitting code to OpenSim

Feature Proposals

Larger changes may require feature proposals depending on whether they introduce or significantly change existing functionality. Please use your judgement to determine whether this is required.

For more details please see the Feature Proposals page.

Developer Documentation

Please be aware that some of this documentation may be out of date. If this appears to be the case then please ask for more information on the mailing lists or IRC channels (details are on the Main Page). If you can't find what you want here you might want to try looking in the User Documentation.






  • Connectors — A description of OpenSimulator's connector architecture, used for linking region code with services (asset, inventory, etc.) in both local (standalone) and distributed (grid) configurations.
  • Services - A description of the grid and simulator services used by OpenSimulator.


  • LLUDP ClientStack - Information on the LLUDP client stack used by OpenSimulator to send and receive UDP packets from viewers implementing the Linden Labs virtual environment protocol.
  • Communication Protocols - Introduction to the various communication protocols used by OpenSimulator. This includes viewer to OpenSimulator TCP and UDP protocols, inter-region protocols and grid service protocols. It also details methods by which arbitary UDP and TCP messages can be sent back and forth between clients/modified viewers and OpenSimulator region modules.
  • Agent Domain / Service - Details about the GridForge hosted Agent Domain/Service code (legacy doc since this LL inspired work has long been abandoned).


  • Database Documentation — Information on the database schemas used in OpenSimulator
  • MonoSqlite — How the database model currently works.
  • LSL:PrimitiveParams — Notes on converting SL Edit GUI values and LSL PrimitiveParams to OpenSimulator PrimitiveBaseShape fields

Entity Transfer

  • Logout - information about user logout.
  • SimulatorLoginProtocol - information about user login.
  • Teleports - documentation on how user teleports are handled in different scenarios (within region, within simulator, between simulators, etc.).


  • OpenSim Archives - Opensim Region Archive (OAR) file format.
  • Inventory Archives - OpenSimulator Inventory Archive (IAR) file format
  • Asset Formats - OpenSimulator asset formats. This includes serialized object formats and appearance formats.


  • AuthIntegration - How to integrate external authentication systems (such as web frontends) with OpenSimulator's authentication system.
  • ClothingManipulation - How to set clothing on avatars using external ROBUST service calls.
  • UserManipulation - How to create users in OpenSimulator via external calls through ROBUST (only available when running in grid configuration).
  • RemoteAdmin - How to use the remote admin plug-in. Some functions (e.g. user creation) are only available when running in standalone configuration.
  • RegionIntegration - Integrating a region and the things within it (scene objects, etc.) with external sources of data and webpages.
  • RestConsole - Description how to use the REST remote console
  • REST - Information about the REST interface to assets, inventory, etc.
  • Webinterface - Integrating the external face of OpenSimulator with the web.
  • Services - Contains general information on the default OpenSimulator services (asset, inventory, etc.) and more detailed information of HTTP interfaces for some services.
  • Known Web Interfaces within OpenSim - The set of CAPS, XMLRPC, or REST entry points in the project.







  • Scripting Documentation — How to use scripts and what limitations apply.
  • LSL Status — A list of LSL-functions that are available in OpenSimulator.
  • OSSL — Some information about the OpenSimulator Scripting Language, and how to implement an OSSL function
  • OSSL Script Library/ModSendCommand - A mechanism for in-world scripts to use a generic modSendCommand() and the link_message event to communicate with region modules.
  • OSSL_Script_Library/ModInvoke - A mechanism for region modules to make new functions available to in-world scripts without patching the OpenSimulator runtime.
  • ScriptEngines — Information about script engines (chiefly XEngine).



  • Sound Protocol - Technical information about the sound protocols (e.g. UDP messages between viewer and server).



  • Threading — Information on the way that threads are used in OpenSimulator.


  • Appearance Troubleshooting - Also contains useful information about avatar behave and the relevant message exchanges between the viewer and the simulator.
  • Attachment Protocols - Information on the attachment protocols used by viewers and OpenSimulator.
  • Name Binding - Some information on how OpenSimulator (and Second Life) binds user UUIDs to names (e.g. 25bf6e60-91c0-4d28-8349-ba254cd4388e -> Jane Doe).
  • Userlevel — Explanation of permissions granted via "God Mode"/Admin Status.


A good first point of contact is the #opensim-dev IRC channel. The OpenSimulator developers also hold office hours once a week in-world on Tuesdays at "Wright Plaza" on There is a "Test Hour" on Saturdays, also generally on "Wright Plaza". Both these weekly events are held at 1900UTC in summer time and 2000UTC in winter.

There is also a development mailing list when development discussion takes place.

Recent Git Commits

Add suppression of grid-side "show regions" command in simulator console for Hypergrid setups as well as normal grid. (Justin Clark-Casey (justincc)) (Fri, 25 Jul 2014 01:02:07 +0000)
Add suppression of grid-side "show regions" command in simulator console for Hypergrid setups as well as normal grid. Should have been done in recent commit 6048dfcd Resolves Justin Clark-Casey (justincc) <jjustincc at googlemail dot com> bin/config-include/GridHypergrid.ini
Revert "Write UDP statistics to the log, not just the console (e.g., "show queues")" (Justin Clark-Casey (justincc)) (Fri, 25 Jul 2014 00:56:41 +0000)
Revert "Write UDP statistics to the log, not just the console (e.g., "show queues")" Fixes It can't be done this way because the stats data needs to show up on the console at all log levels, not just debug. But this means setting it to log at fatal, which is not appropriate for this stuff in the log. I understand the desire but this has to be done some other way, perhaps by (yet another) config parameter. Also, this was already being done with the ClientStatsReport but that also should be done in another way, I think. This reverts commit 5d534127663899cd5592c865b1d00855fce25854. Justin Clark-Casey (justincc) <jjustincc at googlemail dot com> OpenSim/Framework/Monitoring/StatsManager.cs
Add missing default female hair texture for Ruth avatar. (Justin Clark-Casey (justincc)) (Thu, 24 Jul 2014 19:03:19 +0000)
Add missing default female hair texture for Ruth avatar. This was not in library assets despite being referred to in assets/BodyPartsAssetSet/base_hair.dat Texture ID is 7ca39b4c-bd19-4699-aff7-f93fd03d3e7b Taken from Justin Clark-Casey (justincc) <jjustincc at googlemail dot com> bin/assets/TexturesAssetSet/TexturesAssetSet.xml
Fix recent regression in 3c6becd5 where login or hg login to variable sized regions failed with outdated simulator message. (Justin Clark-Casey (justincc)) (Tue, 22 Jul 2014 17:01:54 +0000)
Fix recent regression in 3c6becd5 where login or hg login to variable sized regions failed with outdated simulator message. I forgot that a null 'their version' would not be passed over the wire and ends up as an empty string instead (like older simulators). So instead pass through the correct simulator protcol version instead (SIMULATOR/0.3) when querying from login or hg login. Also removes a debug console write for agent limit accidentally left in for the same commit. Relates to mantis 7276 Justin Clark-Casey (justincc) <jjustincc at googlemail dot com> .../Simulation/LocalSimulationConnector.cs
minor: convert tabs to spaces that got in on recent commit 4a9282e (Justin Clark-Casey (justincc)) (Mon, 21 Jul 2014 22:58:30 +0000)
minor: convert tabs to spaces that got in on recent commit 4a9282e Justin Clark-Casey (justincc) <jjustincc at googlemail dot com> .../Handlers/Profiles/UserProfilesHandlers.cs

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