Asuswrt is the name of the firmware developed by Asus for use on all their recent routers. It was originally based on Tomato, and got extensively modified by Asus over the years as they added their own features to it.
Asuswrt-Merlin is an alternative, customized version of that firmware. Developed by Eric Sauvageau, its primary goals are to enhance the existing firmware without bringing any radical changes, and to fix some of the known issues and limitations, while maintaining the same level of performance as the original firmware. This means Asuswrt-Merlin retains full support for NAT acceleration (sometimes referred to as "hardware acceleration"), enhanced NTFS performance (through the proprietary drivers used by Asus from either Paragon or Tuxera), and the Asus exclusive features such as AiCloud or the Trend Micro-powered AiProtection. New feature addition is very low on the list of priorities for this project.
- RT-AC66U_B1 (same firmware as the RT-AC68U)
- RT-AC68U (including revisions C1 and E1)
- RT-AC68P (same firmware as RT-AC68U)
- RT-AC68UF (same firmware as RT-AC68U)
- RT-AC1900 (same firmware as RT-AC68U)
- RT-AC1900P (same firmware as RT-AC68U)
- RT-AC86U (starting with version 382.1)
- RT-AC2900 (same firmware as RT-AC86U)
- RT-AX3000 (same firmware as RT-AX58U)
(Note: the U, R and W variants are all supported, as they are the exact same hardware and firmware, only different marketing SKUs or different case color)
No longer supported:
Forks and variants
There are also a number of illegal forks which run on non-Asus routers. Asuswrt cannot legally be run on these, as they are not licensed for use of the proprietary components like Trend Micro's engine. These illegal forks are not supported, and should not be used. In addition they are generally in violation of GPL licensing terms, as their source code is not publicly available.
Asuswrt-Merlin has a rich ecosystem that consists of third party developed addons, which can enhance the router with features like ad blocking or connection monitoring. You find more info in the AddOns support forum at SNBForums.