Light is a fork of Firefox where many components (developer tools, less common APIs) have been "slimmed down" or removed entirely to cut load times and improve performance.
You can run the program alongside an existing Firefox installation. We noticed no problems after doing so.
Our first tests suggested Light really does launch much faster than the regular browser, with startup times visibly improved.
Initial RAM use also dropped, although that advantage didn't always seem to remain if we opened multiple tabs.
The browser isn't just about performance tweaks, though. It also supports one or two extras, including "portable mode", where Light can use an INI file rather than Registry settings to find its user and temporary folders.
- "More optimization, better experience"
- "Support portable mode. to use it, rename custom_t.ini to custom.ini"
We're unsure about the RAM savings, but Light does launch very quickly, and as you can run it alongside regular Firefox then that may justify keeping it around.