Possible causes

• Hardware malfunction: In computer graphics, visual artifact
  Visual artifact
  Visual artifacts are anomalies during visual representation of e.g. digital graphics and imagery.-Examples in digital graphics:* Image quality factors, different types of visual artifacts...
  
  s may be generated whenever a hardware component (eg. processor, memory chip, cabling) malfunctions, causing data corruption. Malfunction may be caused by physical damage, overheating (sometimes due to GPU overclocking), etc. Common types of hardware artifacts are texture
  Texture mapping
  Texture mapping is a method for adding detail, surface texture , or color to a computer-generated graphic or 3D model. Its application to 3D graphics was pioneered by Dr Edwin Catmull in his Ph.D. thesis of 1974.-Texture mapping:...
  
   corruption and T-vertices
  T-vertices
  T-vertices is a term used in computer graphics to describe a problem that can occur during mesh refinement or mesh simplification. The most common case occurs in naive implementations of continuous level of detail, where a finer-level mesh is 'sewn' together with a coarser-level mesh by simply...
  
   in 3D graphics, and pixelization
  Pixelization
  Pixelization is a video- and image-editing technique in which an image is blurred by displaying part or all of it at a markedly lower resolution. It is primarily used for censorship...
  
   in MPEG compressed video.
• Software malfunction: Similarly to hardware malfunction, artifacts may be caused by software issues such as bugs in the algorithms, such as decoding/encoding introducing artifacts into audio or video, or a poor pseudo-random number generator would introduce artifacts into statistical research models.
• Compression
  Compression artifact
  A compression artifact is a noticeable distortion of media caused by the application of lossy data compression....
  
  : Controlled amounts of unwanted information may be generated as a result of the use of lossy compression techniques. One of such cases are the artifacts seen in JPEG
  JPEG
  In computing, JPEG . The degree of compression can be adjusted, allowing a selectable tradeoff between storage size and image quality. JPEG typically achieves 10:1 compression with little perceptible loss in image quality....
  
   and MPEG compression algorithms.
• Aliasing
  Aliasing
  In signal processing and related disciplines, aliasing refers to an effect that causes different signals to become indistinguishable when sampled...
  
  : Digital imprecision generated in the process of converting analog information into digital space due to the limited granularity of digital numbering space. In computer graphics, aliasing is seen as pixelation
  Pixelation
  In computer graphics, pixelation is an effect caused by displaying a bitmap or a section of a bitmap at such a large size that individual pixels, small single-colored square display elements that comprise the bitmap, are visible to the eye...
  
  .

External links

• DPReview: Glossary: Artifacts