List of post-release content in Splatoon

"Callie: We've got some update information to share! Marie: What is it? What is it?!"

- Squid Sisters

Downloadable content, or DLC, is additional post-launch content released for Splatoon. Nintendo of America's official Twitter has stated that "Every week or two, new free content will be introduced in #Splatoon, including weapons, stages and gear."

N-ZAP '85
The N-ZAP '85 is a shooter type weapon released on June 1st, 2015. It is very similar in stats to the Splattershot Jr., but lacks its range. Its sub weapon are Splat Bombs and its special weapon is the Echolocator. To unlock this weapon, one must reach level 5, and pay 3,500 coins.

Inkbrush
The Inkbrush is a roller type weapon that has thinner Ink coverage than its Splat Roller and Dynamo Roller siblings, but allows the player to move significantly faster. It was released on June 5th, 2015. To unlock this weapon, one must pay 4,800 coins and be at an unknown level.

Port Mackerel
Port Mackerel is a stage that was released on June 1st, 2015. Like the majority of the other maps, it is symmetrical, and like Kelp Dome it has multiple isles.

Kelp Dome
Kelp Dome is a stage that was released on June 10th, 2015. Like the majority of the other maps, it is symmetrical and contains a larger center area.

Ranked Battle
Ranked Battle is a mode category that features more competitive modes. It was locked until enough players worldwide reached level 10 online. It was released on June 1st, 2015.

The first Ranked Battle mode, Splat Zones, where two teams fight for control of predetermined locations on a stage, was also released on June 1st, 2015 (along with the category itself).

Weapons
The Prima Guide featured numerous upcoming DLC weapons. The list includes:
 * Carbon Roller
 * Custom E-Liter 3K
 * E-Liter 3K Scope
 * N-ZAP '89
 * L-3 Nozzlenose
 * Splash-o-matic

Tower Control
Tower Control is an upcoming Capture the Flag style Ranked Battle mode that will be released post-launch, presumably before August.

Rainmaker
Virtually nothing has been revealed of the Ranked Battle Rainmaker mode other than its name.

August Update Event
This August, a "huge matchmaking update" is expected. This will add a slew of new matchmaking features, including friend-based matchmaking. This will allow either 4 Wii U friends to team up against another group of 4 Wii U friends, or allow 8 Wii U friends to secure a lobby for themselves, where the group will be able to decide the stage and ruleset.