KDFW signed on the air on December 3, 1949, as CBS affiliate KRLD-TV, under the ownership of the KRLD Radio Corp. subsidiary of the Times-Herald Printing Co. (owner of the now-defunct Dallas Times-Herald).
On July 2, 1995, KDFW replaced KDAF (UHF channel 33) as the Fox affiliate for the Dallas-Fort Worth Metroplex, as a result of an affiliation agreement between Fox and New World Communications, which had purchased channel 4 from Argyle Television in a group deal just prior to the agreement's signing in May 1994. The deal between Fox and New World also resulted in the CBS affiliation that KDFW had held since its December 1949 sign-on transferring to Gaylord Broadcasting-owned KTVT. Around this time, the station also changed its branding to Fox 4 Texas, unifying its brand to fall in line with the News 4 Texas titling it had been using for its newscasts since 1990.
In November 1996, the station's on-air brand was altered to simply Fox 4, which has remained in use ever since, concurrent with the re-titling of the station's newscasts as Fox 4 News, and also changing the names of its weather and sports branding to Fox 4 Weather and Fox 4 Sports, respectively; all three segment names have also remained in use ever since, as well as the Fox network logo in the ID.
The branding change occurred as New World was in the process of being sold to the News Corporation, which announced its acquisition of the group in July 1996, and would KDFW place under the control of Fox Television Stations (making it the second Fox O&O in the Dallas-Fort Worth market, after KDAF, which Fox owned from 1986 to 1995).
This logo branding, first seen on sister station WTVT in Tampa-St. Petersburg, and is currently in use by most of the Fox O&Os as well as some Fox affiliates owned by different companies other than Fox, is based on the Fox News logo; with their website names ("myfox(city name).com") based off the domain for the social network Myspace, which was briefly owned Fox's then-parent company the old News Corporation (now 21st Century Fox, then later Fox Corporation).