Webb was born in Santa Monica, California, on April 2, 1920, son of Samuel Chester Webb and Margaret (née Smith) Webb. He grew up in the Bunker Hill section of Los Angeles. His father left home before Webb was born, and Webb never knew him.

In the late 1920s and early 1930s, Webb lived in the parish of Our Lady of Loretto Church and attended Our Lady of Loretto Elementary School in Echo Park, where he served as an altar boy. He then attended Belmont High School, near downtown Los Angeles. Webb was elected student body president of his high school. He wrote to Belmont’s student body in the 1938 edition of its yearbook, Campanile, “You who showed me the magnificent warmth of friendship which I know, and you know, I will carry with me forever.” Webb attended St. John’s University, Minnesota, where he studied art.

Following his discharge, he moved to San Francisco, where a wartime shortage of announcers led to a temporary appointment to his own radio show on ABC’s KGO Radio. The Jack Webb Show was a half-hour comedy that had a limited run on ABC radio in 1946. Prior to that, he had a one-man program, One Out of Seven, on KGO in which he dramatized a news story from the previous week.

Webb’s personal life was better defined by his love of jazz than his interest in police work. He had a collection of more than 6,000 jazz recordings. Webb’s own recordings reached cult status, including his deadpan delivery of “Try A Little Tenderness”. His lifelong interest in the cornet allowed him to move easily in the jazz culture, where he met singer and actress Julie London. They married in 1947 and had daughters Stacy (1950–1996) and Lisa, born 1952. They divorced in 1954. He was married three more times after that, to Dorothy Towne for two years beginning in 1955, to former Miss USA Jackie Loughery for six years beginning in 1958, and to his longtime associate, Opal Wright, for the last two years of his life.

Webb had a featured role as a crime-lab technician in the 1948 film He Walked by Night, based on the real-life murder of a California Highway Patrolman by Erwin Walker. The film was produced in semidocumentary style with technical assistance provided by Detective Sergeant Marty Wynn of the Los Angeles Police Department (LAPD). He Walked By Night’s thinly veiled fictionalized recounting of the 1946 Walker crime spree gave Webb the idea for Dragnet: a recurring series based on real cases from LAPD police files, featuring authentic depictions of the modern police detective, including methods, mannerisms, and technical language.

By 1949, he had abandoned comedy for drama, and starred in Pat Novak, for Hire, a radio show originating from KFRC about a man who worked as an unlicensed private detective. The program co-starred Raymond Burr. Pat Novak was notable for writing that imitated the hard-boiled style of such writers as Raymond Chandler, with lines such as: “She drifted into the room like 98 pounds of warm smoke. Her voice was hot and sticky—like a furnace full of marshmallows.”. Earlier in year Webb served as the main antagonist of Alan Ladd’s protagonist character Dan Holliday in “The Better Man” episode of the radio series “Box 13”, which aired on January 2, 1949.

With much assistance from Sgt. Marty Wynn and legendary LAPD chief William H. Parker, Dragnet premiered on NBC Radio in 1949 and ran till 1957. It was also picked up as a television series by NBC, which aired episodes each season from 1952 to 1959. Webb played Sgt. Joe Friday and Barton Yarborough co-starred as Sgt. Ben Romero. After Yarborough’s death, Ben Alexander joined the cast.

In Dragnet’s early days, Webb continued to appear in movies, notably as the best friend of William Holden’s character in the 1950 Billy Wilder film as Artie Green, assistant director and fiancé to script reader Betty Schaefer (Nancy Olson) in Sunset Boulevard. In 1950, Webb appeared alongside future 1960s Dragnet partner Harry Morgan in the film noir Dark City. In contrast to the pair’s straight-arrow image in Dragnet, here Webb played a vicious card sharp in Dark City and Morgan a punch-drunk ex-fighter. Also in 1950, Webb appeared in The Men, the film in which Marlon Brando made his film debut. Both actors played paraplegics undergoing rehabilitation at a veterans’ hospital. In a subplot, Webb’s character, a cynical intellectual, is fleeced of his life savings by a woman who feigns romantic interest.

In 1951, Webb introduced a short-lived radio series, Pete Kelly’s Blues, in an attempt to bring the music he loved to a broader audience. That show became the basis for a 1955 film of the same name. In 1959, a television version was made. Neither was very successful. Pete Kelly was a cornet player who supplemented his income from playing in a nightclub band by working as a private investigator.

In announcing his vision of Dragnet, Webb said he intended to perform a service for the police by showing them as low-key working-class heroes. Dragnet moved away from earlier portrayals of the police in shows such as Jeff Regan and Pat Novak, which had often shown them as brutal and even corrupt. Dragnet became a successful television show in 1952. Barton Yarborough died of a heart attack in 1951, after filming only two episodes, and Barney Phillips (Sgt. Ed Jacobs) and Herbert Ellis (Officer Frank Smith) temporarily stepped in as partners. Veteran radio and film actor Ben Alexander took over the role of jovial, burly Officer Frank Smith. Alexander was popular and remained a cast member until the show’s cancellation in 1959. In 1954, a full-length feature-film adaptation of the series was released, starring Webb, Alexander, and Richard Boone.

Webb’s most famous motion-picture role was as the combat-hardened Marine Corps drill instructor at Parris Island in the 1957 film The D.I., with Don Dubbins as a callow Marine private. Webb’s hard-nosed approach to this role, that of Drill Instructor Technical Sergeant James Moore, would be reflected in much of his later acting. But The D.I. was a box-office failure.

In 1963, Webb took over from William T. Orr as executive producer of the ABC/Warner Bros. detective series 77 Sunset Strip. He brought about wholesale changes in the program and retained only Efrem Zimbalist, Jr., in the role of private detective Stuart Bailey. Gone were co-stars Roger Smith and Edd Byrnes and the lively series set. The altered program began with Bailey quietly entering an elevator to an upper floor of a bleak office building. The story lines were far different from those of the first five years of the series. The result was a disaster, and critics accused Webb of being out of touch with the younger generation, a perception that the revival of Dragnet subsequently did nothing to correct. Ratings fell, and 77 Sunset Strip was cancelled before the end of the sixth season. John Gavin’s Destry, a light-hearted Western series, filled the remaining three months of the Friday-night time slot vacated on ABC by 77 Sunset Strip.

Meanwhile, Webb teamed with actor Jeffrey Hunter to form Apollo Productions. They produced a failed television series, Temple Houston, with Hunter in the title role. In the summer of 1963, Webb pushed Temple Houston to production. The series was loosely based on the life of the frontier lawyer Temple Lea Houston, the youngest son of the legendary Texan Sam Houston. The series was added to the NBC schedule after the planned drama, The Robert Taylor Show, based on case files of the United States Department of Health, Education and Welfare, was suddenly disbanded after making four episodes. Under orders from Webb, Temple Houston episodes were put together in just two or three days each, something previously thought impossible in television production. Work began on August 7, 1963, with the initial airing set for September 19. Jimmy Lydon, a former child actor, adult actor, and a television producer with Warner Bros. at the time, recalled that Webb told the staff, “Fellas, I just sold Temple Houston. We gotta be on the air in four weeks; we can’t use the pilot, we have no scripts, no nothing–do it!” Lydon recalled the team having worked around the clock to get Temple Houston on the air. Co-producer William Conrad directed six episodes, two scripts simultaneously on two different soundstages at WB. “We bicycled Jeff (series star Jeffrey Hunter) and Elam (supporting star Jack Elam) between the two companies, and Bill shot ’em both in four-and-a-half days. Two complete one-hour shows!” recalled Lydon.

Temple Houston ended after its 26-week run. In a 1965 interview with The Milwaukee Journal, Hunter described the situation:

Shortly after leaving his position at Warner Bros., Webb teamed with Universal Television to begin work on a new Dragnet series. A pilot telefilm, based on the Harvey Glatman serial killings, was produced in 1966 for NBC, with Webb’s Sgt. Joe Friday joined by Harry Morgan as Officer Bill Gannon. Webb had tried to get Ben Alexander to reprise his role as Frank Smith, but he was unable to get Alexander to leave the ABC series Felony Squad.

The new Dragnet premiered as a midseason replacement series on January 12, 1967, and aired until April 16, 1970. To distinguish it from the original series, the year of production was added to the title (Dragnet 1967, Dragnet 1968, etc.). The revival emphasized crime prevention and outreach to the public. Its attempts to address the contemporary youth-drug culture (such as the revival’s first episode, “The LSD Story”, guest-starring Michael Burns as Benjamin John “Blue Boy” Carver, voted 85th-best TV episode of all time by TV Guide and TV Land) have led certain episodes on the topic to achieve cult status due to their strained attempts to be “with-it”, such as Joe Friday grilling “Blue Boy” by asking him, “You’re pretty high and far out, aren’t you? What kind of kick are you on, son?” Don Dubbins, who had acted alongside Webb in The D.I. in 1957, was another featured actor in Mark VII Limited programs beginning in the 1960s.

In 1968, Webb and his production partner R.A. Cinader launched Adam-12 on NBC. A spinoff of Dragnet, Adam-12 starred Martin Milner and Kent McCord as a pair of LAPD beat cops, and followed their escapades while on patrol. Running till 1975, for a total of seven seasons, Adam-12 was Webb’s second-longest running television series, with the eight seasons recorded by the original Dragnet being the longest.

Also in 1968, Webb and Johnny Carson performed a sketch on The Tonight Show that has since become known as the “Copper Clapper Caper” sketch. Webb, in character as Joe Friday, was working on the case of a robbery at a school-bell factory. Carson played the owner of the factory and victim of the theft, which consisted of each bell being relieved of its clapper (the device that makes the bell ring). The sketch’s dialogue consisted of Webb and Carson discussing the situation in deadpan style and using alliteration and tongue twisters to describe the incident, each word having either a “c” or “cl” sound at the beginning. Both Webb and Carson tried desperately not to lose composure, but both did, near the end of the sketch.

In 1970, Webb decided to bring an end to Dragnet and cease acting to focus on expanding Mark VII Limited’s production profile. In 1971, Webb entered the world of district attorneys and federal government work with two series. The first, The D.A., starred Robert Conrad and Harry Morgan as a pair of Los Angeles County ADAs, with Conrad playing a junior ADA and Morgan his superior. The second, O’Hara, United States Treasury, was a co-production of Webb and David Janssen, the former star of The Fugitive and future star of Harry O, for CBS (a rare non-NBC Mark VII effort) and featured Janssen as a Nebraska county sheriff-turned-United States Treasury Department agent. Neither series lasted very long, as The D.A., Webb’s last 30-minute series, was cancelled after 15 episodes and O’Hara ended after 22.

Emergency! ran as part of NBC’s Saturday-night lineup for six entire seasons, and it was a popular series, sometimes winning its time slot against CBS’s popular Saturday-night comedy block, which included All in the Family. The series came to an end in 1977, but it spawned a series of telefilms that ran until 1979. Webb’s company and Universal also contracted with animator Fred Calvert to produce a spin-off Saturday-morning cartoon show for NBC titled Emergency +4, which ran for three seasons (the last in reruns) and featured the paramedics Gage and DeSoto assisted by four youngsters and their three pets.

Emergency! was Webb’s last sustained success. Of the remaining series his company produced, the only two that lasted longer than one season were Hec Ramsey, a two-season component of the NBC Mystery Movie wheel series that featured former Have Gun – Will Travel star Richard Boone as a pioneering forensic scientist in the Old West, and Project UFO, an anthology based on the investigations into UFOs as compiled by Project Bluebook that also ran for two seasons beginning in 1978.

Despite his string of short-lived series in the late 1970s, Webb still kept trying to recapture his previous success and decided to bring Dragnet back to television for a third series in 1983. Five scripts had been produced and Kent McCord, one of the stars of Adam-12, was cast as Joe Friday’s new partner.

In 1987, Dan Aykroyd and Tom Hanks starred in a movie parody (and homage) to Webb, titled Dragnet, along with Harry Morgan, who reprised his role from the television series as Bill Gannon, who had by now become a captain of detectives. The comedy film was written and directed by Tom Mankiewicz, in his directorial debut. Aykroyd played the role of Joe Friday, described as the namesake nephew of the original series lead, while Hanks co-starred as Detective Officer Pep Streebeck, Friday’s new smart-alecky and streetwise partner.

Webb has two stars on the Hollywood Walk of Fame, one for radio (at 7040 Hollywood Boulevard) and the other for television (at 6728 Hollywood Boulevard). In 1992, Webb was posthumously inducted into the Television Hall of Fame.

Stacy Webb authorized and collaborated on a book, Just the Facts, Ma’am: The Authorized Biography of Jack Webb, Creator of Dragnet, Adam-12, and Emergency!, of which Daniel Moyer and Eugene Alvarez were the primary authors. It was published in 1999. Stacy did not live to see the publication of the book, having been killed in a collision with a California Highway Patrol car three years earlier.