DEVGRU, or the Naval Special Warfare Development Group, is the United States Navy component of the Joint Special Operations Command (JSOC) and is also known as SEAL Team Six. DEVGRU is responsible for developing new tactics and equipment for the general Navy SEAL organization. The unit is made up of SEALs selected from existing SEAL Teams and is considered a "Tier One" special mission unit, similar to the Army's Delta Force. The Naval Special Warfare Development Group (NSWDG), abbreviated as DEVGRU ("Development Group")[note A] and commonly known as SEAL Team Six, is the United States Navy component of the Joint Special Operations Command (JSOC). The unit is often referred to within JSOC as Task Force Blue. DEVGRU is administratively supported by Naval Special Warfare Command and operationally commanded by JSOC. Most information concerning DEVGRU is designated as classified, and details of its activities are not usually commented on by either the United States Department of Defense or the White House. Despite the official name changes, "SEAL Team Six" remains the unit's widely recognized moniker. 

DEVGRU and its Army and Air Force counterparts, Delta Force and 24th Special Tactics Squadron, are the U.S. military's primary Tier 1 special mission units tasked with performing the most complex, classified, and dangerous missions directed by, until 2002, the National Command Authority, and since then, directly from the President or the Secretary of Defense. DEVGRU conducts various specialized missions such as counterterrorism, hostage rescue, special reconnaissance, and direct action (short-duration strikes or small-scale offensive actions), often against high-value targets. The origins of DEVGRU are in SEAL Team Six, a unit created in the aftermath of Operation Eagle Claw. During the Iran hostage crisis in 1979, Richard Marcinko was one of two U.S. Navy representatives for a Joint Chiefs of Staff task force known as the TAT (Terrorist Action Team). The purpose of the TAT was to develop a plan to free the American hostages held in Iran. In the wake of the disaster at the Desert One base in Iran, the Navy saw the need for a full-time counter-terrorist unit and tasked Marcinko with its design and development.

DEVGRU is divided into color-coded line squadrons:

• Red Squadron (Assault)
• Blue Squadron (Assault)
• Gold Squadron (Assault)
• Silver Squadron (Assault)
• Black Squadron (Intelligence, Reconnaissance, & Surveillance)
• Gray Squadron (Mobility Teams, Transportation/Divers, QRF)
• Green Team (Selection/Training)

Each assault squadron, usually led by a Commander (O-5), is divided into three troops of enlisted SEALs, often called assaulters. Each of these troops is commanded by a senior commissioned officer, which is usually a Lieutenant Commander (O-4). A troop chief also serves as an adviser to the troop commander and is the highest-enlisted SEAL in the troop, usually a Master Chief Petty Officer (E-9). A DEVGRU troop is further divided into smaller teams of SEALs. Each troop has around 16 members and is led by a senior commissioned officer, as well as a troop chief.[28] These individual teams of assaulters are led by senior enlisted SEALs; usually a Senior Chief Petty Officer (E-8), sometimes a Chief Petty Officer (E-7). The rest of these teams are filled out with more Chief Petty Officers (E-7), Petty Officers First Class (E-6), and Petty Officers Second Class (E-5); each member with a respective role. Each assault squadron also has a specific nickname. Examples include Gold Squadron's Crusaders, Red Squadron's Indians, Blue Squadron's Pirates, Silver Squadron's Headhunters, and Gray Squadron's Vikings. The assault squadrons are supported by a variety of support personnel, including cryptologists, communicators, EOD technicians, dog handlers, and sometimes airmen from the United States Air Force 24th Special Tactics Squadron, the Air Force's JSOC element. According to the Government Accountability Office report on special operations forces, in the fiscal year of 2014, DEVGRU had a total of 1,787 authorized positions, of which 1,342 are military and 445 are civilian.