What is OpenSimulator?
OpenSimulator (or OpenSim) is an open-source platform that allows you to create and host 3D virtual worlds. It is similar to Second Life in concept, but it gives users more freedom to run their own virtual environments.

Origins:
OpenSimulator was started in 2007 as a free alternative to Second Life. It supports the same basic functionality: avatars, 3D environments, scripts, objects, and interaction.

What is a Grid?
A “grid” in OpenSimulator is a network of connected virtual regions (also called “sims”). A grid has:

• A login service
• User accounts
• Assets (like objects, clothing, etc.)
• A map of all its regions

Examples:

• OSGrid,
• Kitely,
• DigiWorldz,
• Metropolis (legacy),
• etc.

What is the Hypergrid?
Hypergrid is a technology that connects different grids together. It allows avatars to travel from one grid to another without needing separate accounts on each one. Think of it as interlinked islands in the larger “Metaverse” of OpenSimulator.

Accounts and Travel
You only need one account on one grid, and you can use it to teleport to other grids that are Hypergrid-enabled. Just search for destinations by using their Hypergrid address (usually in the format gridurl:port:regionname).

Firestorm Viewer is one of the most popular viewers for both Second Life and OpenSimulator.
To download the OpenSim-specific version:

• Go to the official Firestorm Viewer website: https://www.firestormviewer.org/
• Click on the Downloads section.
• Find the section titled Firestorm for OpenSim (make sure not to choose the Second Life-only version).
• Download the version appropriate for your operating system (e.g., Windows).

• After downloading the installer (.exe file), double-click it to begin installation.
• Follow the prompts of the setup wizard:
• Accept the license agreement
• Choose an installation folder (default is usually fine)
• Let it install any necessary dependencies
• Once installed, you will find a shortcut on your desktop or in your start menu labeled Firestorm Viewer for OpenSim.
• Launch the viewer.

The first time you open it, go to Preferences > OpenSim and make sure your grid (like Kitely or OSGrid) is listed there. If not, you can manually add it using the grid's login URI. With the “Shork Group HQ” grid still being rather experimental, we recommend friends of the Shork Group to use a more established grid, like OSGrid or Kitely.

As a note: In OpenSimulator grids you have a personal name and a family name. In viewers, you usually have only one field to enter your name, This might be confusing the first time. The solution is to enter your personal name followed by an empty space and then your family name. This is a part-solution to offset the fact that most OpenSimulator grids still can't use HTTPS. It is in the works, but it's a complex topic. Accordingly, do not re-use a passwort for OpenSimulator grids.

• Go to https://www.kitely.com/
• Click Sign Up in the top-right corner.
• Fill in the required details: email, username, password, etc.
• Once registered, log in to your Kitely dashboard.
• When you launch the Firestorm Viewer, select “Kitely” from the grid list and log in with your new account.

• Go to http://www.osgrid.org/
• Click Join on the homepage or visit: http://www.osgrid.org/index.php/create-account
• Fill in your details, including avatar name, password, and email.
• Once done, open Firestorm, select OSGrid from the grid list, and log in with your new account.
• You're now ready to explore OpenSimulator's vast and creative universe!

There are many ressources for Opensimulator available on the Internet. First of all, many Know-How questions and tutorials for Second Life are valid for OpenSimulator, too, as they both share the same core technology and philosophy. However, places, locations, services and people , read “Content” are completely separated between OpenSimulator and Second Life. Second Life is inherently a commercial platform like, well, the first, real, life. OpenSimulator uses the same technology, but is most of all a freely usable universal simulation, construction and interaction platform.
But let's provide you with a set of useful ressources:

• OpenSimWorld - Sim / Location search engine for the Hypergrid

• Opensimulator Grid Listing
• Active Grids Listing in HyperGrid Business
• OSGrid - Oldest and biggest OpenSimulator grid, modular and with research
• Kitely - The biggest commercial OpenSimulator grid with advanced features.

• Outworldz OpenSource Scripts for learning basic scripting for future avatar functions.
  ⇒ Archive.org backup of the Outworldz main page
• Avatar Workbench - SL/Opensimulator Reference Avatars+ Bento Skeleton and bodymodel for Blender
  ⇒ Archive.org Backup for the Avatar Workbench
• Robinwood's SL Tutorials which were used to learn about how to paint the SL/Opensim avatar body textures. His UV Maps were also used to create our Alpha layers.
  ⇒ Robinwood's SL Tutorials on archive.org - as an emergency backup.
• MAX - OpenSource Mesh Avatar for SL & OpenSim
• Ruth & Roth - v2 - OpenSimulator Default Mesh Avatar for SL & OpenSim
• BVHPlay a simple offline BVH Anmation viewer
• Freely usable MOtion CAPture files from Carnegie-Mellon University - BVH format for SL & OpenSimulator
• "MiceOnABeam" Second Life & OpenSimulator Scripting tool
  ⇒Archive.org Backup of https://miceonabeam.com/
• Scriptastic! - a Scratch-like visual scripting tool for LSL for SL & OpenSim
• UV-Mapping for Blender HowTo - Explains how to do UVMapping on 3d Models in Blender - Required for the following entry!
• UCUPaint for Blender HowTo - Explains how to use Blender and a Plugin to paint 3d models
• MakeHuman Community - Toolkit / Utility for use with Blender to create SL/OpenSimulator conformant avatars and components such as clothing
• https://stableprojectorz.com/ - Website & Video to learn making mesh clothes for SL and OS.
• The OSGrid Wiki - The wiki for and about all things OSGrid and thus also OpenSim