Parallelism

Elements that are parallel to each other are perceived as being related.

Elements that are parallel to each other are seen as more related than elements not parallel to each other.

Parallelism is a Gestalt principle that suggests people perceive elements as being related when they are pointing in the same direction or follow a similar path. In user interface design, this means that even if items are different shapes or colours, our brains will naturally group them together if they are oriented in parallel. This mental shortcut helps users quickly make sense of complex layouts by creating an underlying sense of order and connection without needing extra borders or lines to separate them.

When designers use parallel elements, they can guide a user's eye across a page more effectively. For example, if you have a series of slanted cards or diagonal call-to-action buttons that all lean at the same angle, the viewer will intuitively feel that these items belong to the same category or serve a similar purpose. This is a powerful way to create a visual rhythm that feels intentional and organised, rather than cluttered or random.

However, it is important to use this principle carefully so as not to confuse the user. If too many different groups of elements use various parallel angles, the layout can quickly become overwhelming and lose its sense of harmony. The best use of parallelism is to reinforce the relationship between specific pieces of content, ensuring that the most important information stands out because it follows a consistent and predictable visual flow.