Host applications

Host applications or plugin hosts are graphics applications that are capable of running plugins. Photoshop fully supports all available plugin types; certain Adobe hosts, like Photoshop Elements and Fireworks, support most of them, while Lightroom supports many and also has its own, derived from the Photoshop format.

Many non-Adobe commercial graphics applications also support Photoshop-compatible plugins – Paint Shop Pro,^[4] PhotoImpact, and Corel PhotoPaint are some of the better-known ones. There are several dozen more plugin hosts, including lesser-known products like Chasys Draw IES, the free-software image editor GIMP, and viewers like IrfanView.^[5] However, the majority of non-Adobe hosts support filter plugins only, and many of them do not even support all available filter plugins. More Microsoft Windows hosts support the plugins, though an increasing number of Mac applications support the Mac Photoshop plugin packages.

Third-party support for plugins was fairly broad and rapid after the release of the Photoshop SDK and API containing the specifications for Photoshop plugins. Non-Adobe implementation contracted and fragmented in 2002, when Adobe restricted access to the SDK and made the developer license more expensive. Developers of other image applications had limited or no access to it any longer, and in many cases either did not support newer plugin features or simply did not implement Photoshop plugin support at all. Plugin developers faced a dilemma: either support the new features that appeared in Photoshop 7 and later versions, like access to layers, but lose compatibility with various other image applications; or use the old SDK version which already included many of the important specifications and make sure their plugins would be supported by all hosts, but at the cost of a smaller feature set.^[1]

Around 2005, Adobe changed the policy again, so that developers could make a request for the SDK via a Web-based form, with no fees, and with all requests handled individually.^[6] It is unclear what criteria have been applied, though third-party implementation of support for Photoshop plugins has increased again, is more consistent (few old plugins have remained viable from the 2000s, as operating systems and have changed in the interim), and the feature remains popular and in demand by users of graphic-editing software.

Some commercial and free projects have also created their own plugin formats, and the general concept (also common among digital audio workstations) has spread to other visual editing applications, including video compositors, 3D modeling suites, and CAD applications.