There are a lot of different kinds of OpenSim grids out there — it can get a little confusing. Well, a lot confusing.

Here’s a quick primer.

Social grids

Social grids attempt to replicate the experience of Second Life. They don’t make up the majority of grids running on the OpenSim platforms, but are among the most visible, since they actively market themselves to attract new members. Membership is normally free, and there is usually a Web registration form.

Social grids often hold in-grid community events, have Websites where users can share photos, online forums, in-grid volunteers to help newcomers, freebie stores, and other social services.

Roughly in order of decreasing size, the largest social grids are: OSGrid, Avination, InWorldz, New World Grid, Metropolis, Meta7, NexXtLife, FrancoGrid, WorldSimTerra, 3rd Rock Grid, MyOpenGrid, ReactionGrid, Open Neuland, Virtyou, Role Play Worlds, Oasis World, AlphaTowne, German Grid, SpotOn 3D, PrimSim, Avatar Hangout, SIM World, Twisted Sky, SimValley, PMGrid, GiantGrid, Pirate Grid, Your Alternative Life, Pseudospace, Craft World, Wilder Westen, Triton Grid, VeeSome, NorthGrid, GerGrid, Ikincihayatim, MetaverseNexus,  Tertiary Grid, and JokaydiaGrid.

Halloween party on OSGrid in 2009. (Photo by Ziah Zhangsun.)

Private grids

Individual companies, non-profit organizations, and educational institutions often set up private grids for their own staffers, students, members, and clients. These private grids make up the vast bulk of the OpenSim grids out there, and are run in quiet mode, since they do not need to advertise for new members.

Examples of such grids are Enclave Harbor,  Virtual Worlds Grid, NZ Virtual World Grid, GovGrid and  Virtual Univ. of Edinburgh.

OpenSim hosting provider ReactionGrid alone is currently hosting more than 100 private grids for its clients. Hundreds — if not thousands — of other private grids are run on institutional servers and behind corporate and campus firewalls.

A private grid can choose to allow hypergrid teleports in and out, can choose to have open registration, and can be hosted with an OpenSim hosting provider, in the cloud, with a commercial server farm or behind a corporate or campus firewall.

One new example of a private grid is Kitely, which only allows access to Facebook users. (Other access options are under development.) Users can get a region up and running for $0.10 a month — that’s ten cents a month — with an additional $0.20 per user per hour. You can set up a brand new region, upload an OAR file, and invite your Facebook group in less than two minutes. It’s a great option for folks who want a lot of land to play in, but don’t expect to get a lot of traffic. Read more here: When do cloud-based sims make sense?

Open grids

Open grids allow anyone to connect a region to the grid. Open grids are often popular with people who host regions on home computers. As a result, they may also be less stable than other grids, as individual regions may go offline at any time.

Many open grids — including OSGrid — are run by non-profit organizations or groups of volunteers.

An increasing number of third-party OpenSim hosting providers are also offering professional region hosting on these grids, at prices as little as $10 a region, providing an easy, cheap way to get regions up and running, yet with a bit more stability than with home-based regions.

Open grids include OSGrid, Metropolis, FrancoGrid, WorldSimTerra, ScienceSim, and MyOpenGrid. OSGrid is the largest of these grids, with more regions and users than all other social grids combined.

Commercial grids

Commercial grids are social grids run by private companies that also rent land on these grids. Some follow the model of Second Life, attempting to create a multi-purpose social environment for their residents. Others focus on narrow niches, such as role playing communities or German-speakers.

Examples of commercial grids include InWorldz,  Meta7, NexXtLife, 3rd Rock Grid, ReactionGrid, Avination, Open Neuland, Virtyou, Role Play Worlds, Oasis World, AlphaTowne, German Grid, SpotOn 3D, PrimSim, Avatar Hangout, Your Alternative Life, Pseudospace, Wilder Westen, VeeSome,  GerGrid, Ikincihayatim, MetaverseNexus, JokaydiaGrid, and Tertiary Grid.

Many commercial grids also follow Second Life’s lead in terms of protecting content. For example, Avination, InWorldz, SpotOn3D and 3rd Rock Grid all have hypergrid teleports turned off, so that their users cannot travel to other grids — and potentially take content to less secure locations. In addition, InWorldz and SpotOn3D restrict the use of region backups (or OARs) since they also result in duplicated content, and allow for the possibility of the content to move to other grids, since an OAR can be uploaded anywhere.

Other commercial grids, including ReactionGrid, Wilder Westen, GermanGrid, JokaydiaGrid and AlphaTowne, do allow hypergrid teleports. And many again, including ReactionGrid and 3rd Rock, allow OAR exports.

These policies can change at any time, however. For example, as hypergrid security improves, more grids are embracing the protocol.

A commercial grid sets its own terms of service and may claim ownership rights or the right to use any of the content on its grid, may limit the types of content allowed on the grid, and may restrict user accounts or privileges.

Hypergrid-enabled grids

More than half of all known OpenSim grids are hypergrid-enabled. Hypergrid allows a user to teleport from one grid to another without relogging or creating a new avatar. Hypergrid allows people to attend meetings on different grids, go shopping, socialize, even build. The latest version of hypergrid, HG 1.5, adds additional protections so that rogue grid operators can’t hack into the inventories of visiting avatars.

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ScienceSim recently turned on in-bound hypergrid teleports (outbound hypergrid teleports are still not permitted, to protect on-grid content.)

To do a hypergrid teleport, a user simply enters a hypergrid address into the Search field in the Map dialog box.

But, just as on the Web, a user can also teleport by clicking on a hyperlink.

In OpenSim, that hyperlink is usually in the form of a hypergate. These gates are normally activated by clicking on them, or walking through them.

Finally, it’s also possible to embed a foreign region onto the map of your grid — this is called “link regions” — so that users can simply click on the map to teleport. The foreign region isn’t actually living on your grid. Having link regions set up is not required for hypergrid teleports to work, it is simply an additional visual convenience for grid residents.

You can find more information about how to hypergrid at Hyperica, our directory of hypergrid destinations.

Behind-the-firewall grids

A behind-the-firewall grid is one –surprise — that’s run behind a corporate or school firewall, on corporate or school servers.

A behind-the-firewall grid can also have outside access enabled via direct login or via hypergrid teleport, if the appropriate ports are opened in the firewall. Without those open ports, a behind-the-firewall grid is the most secure, most private deployment of an OpenSim grid possible.

A company running its own behind-the-firewall grid is not dependent on any third party for hosting services and does not need to abide by any outside terms of service agreements — if you run your own grid, you set your own terms of service.

With a behind-the-firewall grid, no third party ever sees the grid’s content. This can be important for companies in regulated industries, such as health care and financial services.

There are several OpenSim consulting firms that will help you set up your own grid, and who can provide ongoing maintenance and upgrades, if needed.

Hosted grids

A hosted grid is one that’s run by an OpenSim hosting company and resides on servers owned or leased by that hosting company. The customer, however, owns the entire grid and all the content on it.

Many companies that want to have private grids — but don’t have the technical expertise to run them in-house as a behind-the-firewall grid — will get hosted grids instead. Having a private hosted grid is normally as easy and inexpensive — or even more so — then renting regions on an existing grid. And, when labor is taken into account, can be less expensive than running a behind-the-firewall grid, as well.

Like a behind-the-firewall OpenSim grid, a private hosted grid allows grid owners to manage their own users, schedule their own upgrades and maintenance, and, of course, make full backups of all content. However, the OpenSim hosting company has access to the servers and databases, since they need this access to ensure stability of the grid and to handle upgrades and other maintenance.


A typical OpenSim grid is composed of a single central server managing user accounts, storing user inventories,  and keeping track of where every region is on the grid map. Additional servers host the regions themselves.

A mini-grid combines everything on a single server, and is usually anywhere in size between one and 16 regions, though the most common configuration is a four-region minigrid. The more powerful the server, the more regions and user assets it can hold.

A mini-grid is often run as a megaregion — meaning that there are no border crossing hiccups between the regions.

Mini-grids are a cheap and convenient way to get started with a private grid, either hosted or behind-the-firewall. The most popular deployment is the free Diva Distro, which comes with a four-region megaregion and a selection of starting avatars, hypergrid enabled by default, and a simple Web-based user registration panel.

A mini-grid can be upgraded to a full, multi-server grid as needed.

Maria Korolov