Photoshop plugins (or plug-ins) are add-on programs aimed at providing additional image effects or performing tasks that are impossible or hard to fulfill using Adobe Photoshop alone. Plugins can be opened from within Photoshop and several other image editing programs (hosts compatible with the appropriate Adobe’s specifications) and act like mini-editors that modify the image.

Photoshop-compatible plugins fall into several main types: filter plugins .8bf, import plugins (also called 'acquisition') .8ba, export plugins .8be, file format plugins .8bi, and automation plugins .8ly. Also, there are selection plugins 8bs and parser plugins 8by, but no one other than Adobe has ever created plugins of these types.

"Import/export plugins" acquire or write image data from or to certain devices, "file format plugins" open and save less common image formats (not inherently supported by Photoshop), and "automation plugins" automate certain tasks in the manner of Photoshop "actions" (macros).

Host applications or plugin hosts are graphics applications that are capable of running plugins. Many commercial graphics applications support Photoshop-compatible plugins — Photoshop, Paint Shop Pro, Photoshop Elements, PhotoImpact, Corel PhotoPaint, and Adobe Fireworks are the most renowned ones. There are several dozens more plugin hosts, including little known products like Chasys Draw IES, free editors like GIMP (with certain add-ons) and viewers like IrfanView. Much support is limited to the Microsoft Windows platform and .8bf filter plugins.