Webb grew up poor in the Rampart section of Los Angeles. After serving as a crewmember of a B-26 in World War II he starred in a radio show about a private detective, Pat Novak for Hire. Webb had a role in the 1948 police action movie He Walked By Night. The film was made in docudrama style and first gave Webb the idea for Dragnet. After getting assitance from, and riding along with, Los Angeles Police personnel Webb produced Dragnet which premiered in 1949 on the NBC network. Sponsored by Fatima cigarettes, Dragnet starred Webb as Joe Friday and Barton Yarborough as Ben Romero. They played detective sergeants working various divisions. Walter Schumann did the theme song for the show. Webb announced the show in first person as the character Joe Friday and maintained almost fanatical attention to detail and realism. This and his management style alienated many actors.
In 1953 saw Dragnet become an even more successful television show. Unfortunately Barton Yarborough died suddenly and Barney Phillips (Ed Jacobs) and Herb Ellis (Frank Smith) supplanted his partner. Later Ben Alexander would step in as the jovial, burly Frank Smith.
Dragnet began with "The story you are about to see is true. Only the names have been changed to protect the innocent." At the end of each show, the results of the trial of the suspect and severity of sentence were announced by George Fenneman. The television series continued until 1959.
Webb married singer and actress Julie London in 1947 and raised two children. They later divorced and Webb married three more times.
He tried his hand in several movies that did not gain major status at the box office such as The DI, about a US Marine Corps drill instructor, and Pete Kelly's Blues, an evocative film about itinerant jazz musicians in the 1920s.
In 1967 Webb produced and starred in a color version of Dragnet for TV. This costarred Harry Morgan as Officer Bill Gannon. The show's pilot was to air earlier but was shelved until 1969. Over a year later, in concert with Robert A. Cinader, he produced Adam-12 about a rookie and his older partner who patrolled the streets of Los Angeles as uniformed officers Pete Malloy (Martin Milner) and rookie Jim Reed (Kent McCord). The show ran until 1975.
Webb produced The DA with Robert Conrad and O'Hara; US Treasury with David Jannsen. These were short lived, but another show, Emergency proved to be a major success running from 1972 to 1977 and its ratings occasionally even topped its timeslot compettitor, All in the Family. Webb cast his ex-wife, Julie London, and her second husband, Bobby Troup, as nurse Dixie McCall and Dr. Joe Early.
Project UFO was another Jack Webb product and depicted Project Blue Book, a US Air Force investigation into Unidentified Flying Objects. This was the last major product of his Mark VII production company.
He considered resurrecting Dragnet in 1983 with Kent McCord as his partner before he died of a heart attack in 1982. He was interred in the Forest Lawn, Hollywood Hills Cemetery in Los Angeles. Webb was given a funeral with full police honors although he had never actually served in the force.