The strict Hollywood film censorship code enforced from 1934 was the Hays Code, formally called the Motion Picture Production Code. It was named after Will H. Hays, president of the Motion Picture Producers and Distributors of America, the industry's trade organization.
The code was adopted in 1930, but enforcement was initially weak. A major amendment on June 13, 1934, created the Production Code Administration and required films released from July 1 onward to receive a certificate, or Seal of Approval. Joseph Breen became the code's most influential administrator, and under his supervision Hollywood studios submitted scripts and finished films for review.
The rules restricted profanity, nudity, sexual relationships outside marriage, crime portrayed sympathetically, drug use, and other subjects considered morally dangerous. The code also prohibited miscegenation as it was then defined by the industry, reflecting the racism and social prejudices of the era. It was an industry self-regulation system, not a federal censorship law, adopted partly to avoid government intervention and local censorship boards.
The Hays Code gradually weakened in the late 1950s as filmmakers challenged its limits and foreign films, television, and court decisions changed the industry. It was effectively replaced in 1968 by the MPAA's age-based rating system.