Design principles codify the behavioral research and/or design research known about specific User Experience topics.
The term can also be used to describe the driving behavior behind a design or a design group. In other words Fitt's Law is a design principle that explains the relationship between an object and its target. "Set users up for success" is a design principle that describes one of any good company's design goals.
It's worth noting that many of the design principles listed below are Heuristics- that is to say, they're practical methods to decision making sufficient for immediate goals, but not always appropriate for in-depth or complex decisions.
These are the principles that drive how the web functions at the hardware and software level. The closer our designs come to aligning with these principles, the more "native" to the web our designs will be, and the more effective they will be.
- Rough consensus and running code - If everyone agrees we need images, for example, and someone gets images up and running, whoever gets there first will probably be the one setting the direction for the structure.
- Postel's Law- "Be liberal in what you accept and conservative in what you send". In other words, assume that the people who are sending you things don't know the protocol, but stick to the protocol when you send out to someone else.
- Priority of Constituencies - "In case of conflict, consider users over authors over implementers over specifiers, over theoretical purity." According to HTML for Web Designers (1st edition) by Jeremy Keith, this is one of the design principles used by the WHATWG to decide what changes in the HTML specs.
- Small pieces loosely joined describes how avoiding monoliths provides flexibility and paves the ways for APIs.
- Information wants to be free - it may not always be in our best interest for information to want to be free, but for good and for bad this is definitely a founding principle of the web.
Content Strategy principles
These principles are taken from The Elements of Content Strategy by Erin Kissane.
- Good content is appropriate. Publish content that is right for the user and for the business.
- Good content is useful. Define a clear, specific purpose for each piece of content; evaluate content against this purpose.
- Good content is user-centered. Adopt the cognitive framework of your users.
- Good content is clear. Seek clarity in all things.
- Good content is consistent. Mandate consistency, within reason.
- Good content is concise. Omit needless content.
- Good content is supported. Publish no content without a support plan.
- Fitt's law - The time to acquire a target is a function of the distance to and the size of the target.
- Hick's Law - The time it takes to make a decision increases with the number and complexity of choices.
- Jakob's Law- Users spend most of their time on other sites. This means that users prefer your site to work the same way as all the sites they already know.
- Law of Prägnanz- People will perceive ambiguous or complex images as the simplest form possible, because it is the interpretation that requires the least cognitive effort of us.
- Miller's Law (Seven plus or minus two) - The average person can only keep 7 (plus or minus 2) items in their working memory.
- Occam's razor - Among competing hypothesis that predict equally well, the one with the fewest assumptions should be selected.
- Pareto Principle - For many events, roughly 80% of the effects come from 20% of the causes.
- Parkinson's Law - Any task will inflate until all of the available time is spent.
- Progressive Disclosure
- A Sense of Place - Humans need to have a sense of environment, direction, and available tasks to accomplish their goals.
- Serial Position Effect - Users have a propensity to best remember the first and last item in a series.
- Set users up for success
- Tesler's Law (The Law of Conservation of Complexity) - For any system, there is a certain amount of complexity that cannot be reduced.
- Zeigarnik Effect - People remember uncompleted or interrupted tasks better than competed tasks.
Human-Computer Interaction Principles
- Avoid absolute judgement limits
- Make displays legible (or audible)
- Minimizing information access cost
- Principle of consistency
- Principle of Multiple Resources
- Principle of Pictorial Realism
- Principle of Predictive Aiding
- Principle of the moving part
- Proximity Compatibility Principle
- Redundancy gain
- Replace memory with visual information - knowledge in the world
- Similarity causes confusion
- Top-down processing
Visual Design Principles
General Design Principles
- Aesthetic-Usability Effect - Attractive things actually work better.
- Face-ism Ratio - The closer to a face you crop an image, the more you emphasize their personality over their physical appearance.
- Von Restorff Effect (Isolation Effect) - When multiple similar objects are present, the one that differs from the rest is most likely to be remembered.
- Connectedness - Elements that are visual connected are perceived as more related than elements with no connection.
- Figure & Ground
- Proximity - Objects that are near, or proximate to each other, tend to be grouped together
- Similarity - The human eye tends to perceive similar elements in a design as a complete picture, shape, or group, even if those elements are separated.
Characters and Principles of UX
Richard Dalton put together a list of characteristics and principles of UX
For Richard, Characteristics are a vector between two points, and a user may be closer to one side or another. For each of those items we've listed the characteristic, its explanation, and the range from one side to the other. Richard lists only three principles: Relevant, Comprehensible, and Aesthetic. For a deeper explanation of each, access the PDF or visit the website.
Other examples of design principles
- Design Principles - Hands-down the best resource for design principles.
- Creating Etsy's Design Principles by Magera Moon
- Laws of UX by Jon Yablonksi
- The ultimate guide to proper use of animation in UX covers principles specific to animation