A bullet hit squib is a pyrotechnic, practical special effect device used in filmmaking, television and theatre to simulate the appearance of a person or an object being shot. When used on an actor as a blood squib, an explosive charge ruptures the costume and fake blood packet, expelling its contents through the resulting hole. Devices used similarly on props, such as walls and cars, blow out predrilled, filled and painted holes.

For blood hits, the device comprises a squib, simulants sealed in a bag imitating bodily fluids, tissues or both, a protective shield and padding. The device is usually concealed in specially prepared clothing and weakened at the effect location, instead of on bare skin.

The squib is connected to a power source and a remote, detonated by the actor or a crew member to achieve the effect. Multiple squibs may be used and triggered either simultaneously or sequentially to represent different types of gunfire.

While used for dramatic effect to illustrate the demise of a character, the visual result does not accurately reflect the physical characteristics of real gunshot wounds. Nevertheless, the stylised and exaggerated aesthetic is widely recognised by filmmakers and audiences alike, such as in the main figure, bullet holes are blown outwards and blood projects through the entire jacket.

Bullet hit squibs were first used in the film industry as early as 1943 in Bataan, as shown in the adjacent image, and 1955 in Pokolenie, with the latter using fake blood added in a condom and a squib, a technique still widely in use today. The use of squibs in filmmaking has become a widely accepted and well-established technique for creating convincing and realistic depictions of violence. This approach has been used in many classic films such as The Matrix (1999), Goodfellas (1990), and The Terminator (1984).

Despite advances in digital effects, practical squibs are still widely used due to their ability to produce authentic, in-camera effects that enhance the overall atmosphere and intensity of a scene. While CGI can be employed to augment or replace squib effects in certain situations, the physicality and immediacy of practical squibs continue to make them a valuable tool in special effects for film and television. Bullet hit squibs can also be used in first responder moulage training and music videos, for example 99 Problems (2004).

The earliest patent related to the manufacturing and chemical composition of bullet hit squibs was submitted in 1991. Since then, from the 2000s, a number of notable design or manufacturing features have been patented. Advancements include specific methods and chemical compositions to manufacture the squibs themselves, such as without heavy metals; a wearable, reusable pneumatic system that eliminates the need for explosives by using compressed air to expel fake blood through a small outlet. Another design incorporates traditional squibs but is pre-manufactured and nearly fully assembled, reducing on-set assembly time. This standardised design, however, limits customisation in terms of blood volume, spray pattern, etc.

In film productions, multiple crew members, including pyrotechnicians and costume designers, work together to create the effect. Pyrotechnicians are responsible for building the squibs, while costume designers prepare multiple identical outfits for the actors. Collaboration among writers, directors, producers, and actors is essential for determining the number and placement of squibs, as well as costume design. Depending on the budget, productions typically use between three and six, and sometimes eight costumes to accommodate various takes, camera angles, out of sequence filming, dress rehearsals, backups and tests. This can become costly, especially for low-budget filmmakers, leading to trade-offs between the number of character deaths, takes (i.e. costume duplicates), and the number of squibs (i.e. multiple hits) used. An overview of the device and costume preparation is illustrated in the gallery below.