Hard light, alternatively spelled hard-light or hardlight and more formally identified as boson-photon fields, is a Forerunner technology that allows light to be transformed into a solid state, capable of bearing weight and performing a variety of tasks. This involves an as-yet unexplained interplay between coherent, high-energy light and gas particles, such as air.
Hard light was used extensively by the Forerunners for a great variety of purposes. Forerunner control panels and interfaces are almost always made entirely of hard light, and can react to the touch of a Forerunner or human despite their utter lack of mechanical components. Light bridges are another basic application of hard light; these bridges are strong enough to bear the load of heavy objects such as a Scorpion tank, yet can be switched on or off as easily as a normal beam of light. Some of the larger conventional bridges constructed by the Forerunners also feature support cables made of hard light. Hard light is also used in the locking mechanisms of Forerunner doors.
 As structural elements
The most prominent use of hard light is perhaps also its most inconspicuous one; although this is not immediately obvious, hard light construction actually comprises a significant portion of Forerunner architecture. Through the use of highly sophisticated holographic projection technology, hard light can be crafted to be entirely indistinguishable from physical construction such as metal and can form very complex shapes. As such, hard light is commonly used in the composition of Forerunner structures and ships, either for aesthetic purposes, as a covering for mechanical and technological mechanisms, or to form internal divisions and compartments; this allows a Forerunner ship or structure to reconfigure its layout, furnishings or decoration at will. Despite its versatility, hard light construction is susceptible to power failures and as such, the most important supporting structures have to be made of actual matter.
The Halo installations make use of hard light in their firing mechanisms, in addition to using hard light as a protective structural reinforcement to stabilize and protect the rings against tidal and gravitational forces from other objects. Although many Forerunner structures project a hard light decorative shell over the structural support elements of the building, almost all buildings seen on the Halo installations or the Ark lack this covering; the Forerunners did not implement such decoration on the Halos' structures, as they were meant to be purely functional. However, the structures on the Halo rings still employ hard light construction for practical purposes. Additionally, any structures that possess hard light decor only activated in the presence of Forerunners; however, due to their status as Reclaimers, the presence of humans will also activate hard-light decoration in certain structures, as seen in the Menachite Forerunner complex.
Although they can be crafted to be extremely resilient, hard light constructs are not indestructible. Aside from disabling them by deactivating or destroying the power source, hard light constructs can break up upon suffering heavy damage. For example, Installation 07's central hard light hub and spokes connecting to the ring were destroyed under the stress of collision with a planet. The stress of the hard light structures pressing against the face of the planet caused the spokes to first stretch out, before fragmenting and abruptly turning into curling beams of intense, blue-violet radiation.
 In military technology
The Forerunners also used hard light technology to create protective personal shields, such as the Z-90 Photonic Coalescence Emitter/Aegis as it is known by the UNSC, more commonly known as the "hardlight shield," which could be deployed in the battlefield by fighting units like Promethean Knights. After encountering such technology in 2557, UNSC forces were able to adapt these shields for use by Spartan supersoldiers.
Promethean units are also known to incorporate hard light technology into their weaponry and even personal design. For close-quarters combat, Promethean Knights utilize hardlight blades to dispatch opponents. The Z-250 Lightrifle and Z-130 Suppressor are among the known infantry weapons to utilize hard light projectiles. For offensive purposes, they create solid projectiles that can be fired like conventional bullets or plasma bolts. Some units have presumably decorative hard light architecture, notably the fins on the back of the Knight Battlewagon. Hard light was also used as a form of connective mechanism in the limbs of a war sphinx. Forerunner design seeds also made use of hard light. When activated, the rotating pillars of the machine would emit "scaffolding" of hard light that would fabricate a machine or ship using raw materials obtained on-site.
- Hard light was one of the several Forerunner technologies the Covenant never successfully reverse-engineered. Despite this, the properties of the holo-drone demonstrate that they had access to comparable technology.
- There are real-world scientific efforts to manipulate light to behave as a solid surface.
 List of appearances
- Halo: Combat Evolved (First appearance)
- Halo: The Flood
- Halo: First Strike
- Halo Graphic Novel
- Halo 3
- Halo Wars
- Halo: Blood Line
- Halo: Evolutions - Essential Tales of the Halo Universe
- Wages of Sin (First identified as "hard light")
- Halo: Cryptum
- Halo: Primordium
- Halo 4
- Halo: Spartan Assault
- ^ a b Halo 4 Official Site: GAMEPLAY
- ^ Mega Bloks, Special Report: ONI REAP-X
- ^ Halo: Combat Evolved, campaign level Assault on the Control Room
- ^ a b Halo: Evolutions - Essential Tales of the Halo Universe Volume II, "Wages of Sin", page 291
- ^ a b Halo: Primordium, pages 116, 201, 269
- ^ Halo 4
- ^ a b Halo: Cryptum, page 242
- ^ Halo: Cryptum, page 124
- ^ Halo: Cryptum, pages 307, 310
- ^ Halo: Cryptum, page 311
- ^ Halo: Cryptum, page 319
- ^ Halo: First Strike, page 143
- ^ Halo: Primordium, page 334-335
- ^ Halo Waypoint: Halo 4 Interactive Guide
- ^ Halo: Cryptum, pages 93, and 194
- ^ CNN: Scientists create light-matter like Darth Vader's lightsaber