- Most of Second Life's competitors run in web browsers, unlike Second Life which requires you to download and install the client software on your computer.
- Google has launched 'Lively', a browser-based virtual world that runs in a browser but requires users to install propriety software to run it.
- Ogoglio is an open source browser-based virual worlds project where users are allowed to build their own spaces which can be linked up to form a virtual city for work.
- When the UK and US armies were looking to conduct a joint training experiment in a virtual world they chose Forteria Olive instead of Second Life.
- OpenSim, an open-source Second Life competitor built by reverse engineering Second Life's API's and portions of Second Life's code that was open sourced.