What is the ideal usage of placeholder text in input fields?

The ideal usage of placeholder text in input fields is to indicate the type of input expected. Placeholder text serves as a hint or example of what the user should enter in the field, making it easier for users to understand the required format or type of information. For instance, a placeholder might show an example date format (e.g., "MM/DD/YYYY") or suggest a type of input like "Enter your email address" which guides the user clearly on what information is required.

Using placeholder text solely for instructions can lead to confusion, as it may not be seen while the user is actively typing unless the placeholder text is a part of the input field. Replacing field labeling with placeholder text is generally not advisable, as labels provide a more persistent and accessible reference to what the field represents, which is especially important for usability and accessibility. Enhancing graphical appearance is not the primary purpose of placeholder text; while aesthetics can be considered, the functional role of guiding user input is the main focus.