Combo box

Combo box, picker, or radio buttons?#

The text input functionality of the combo box is meant to make large lists easier to search. If you have fewer than 6 items, use radio buttons. If you have more than 6 items, consider whether your list of selections is complex enough to merit searching and filtering. If it's not complex enough for a combo box, you can use a picker.

Suppressing the popover#

It’s okay to suppress the popover when the combo box contains entries the user is familiar with, and when autocomplete is enabled. A suppressed popover can still be opened when the field button containing the chevron is clicked.

Immediate popover launch#

Launch the popover immediately if your user is highly unfamiliar with the content in the combo box, or if the data is especially complex.

Delayed popover launch#

Launch the popover on text change if your user can get started typing without seeing a long list of options.

Saving suggestions#

When a suggestion is appended to the end of typed text, it remains the selected value when focus leaves the field. This guards against the scenario when a user sees a word completed in a field, continues to another form component, and the failure to commit changes erases the suggestion.

When autocomplete is disabled, best matches get a hover style in the popover, but don’t get saved as a value unless they’re clicked on or "Enter" is pressed.

Include a label#

Every combo box should have a label. A combo box without a label is ambiguous and not accessible. In rare cases where a label could be absent, make sure to have the design reviewed and approved by an accessibility expert.

Keep menu items concise#

Keep menu items short and concise. Long menu items that cause text to wrap to multiple lines are discouraged. If text wrapping becomes a frequent concern, consider revising the text or use alternative UI patterns that will give your content more space.

Truncation#

Choose a width for your combo boxes that is likely to accommodate the majority of selections available within it. When a combo box is in focus and the typed input exceeds the width of the field, push the leftmost text out of sight while allowing text to continue to be entered towards the chevron. When a combo box is deselected, truncate the selected entry with ellipsis before it collides with the chevron button.

Follow capitalization rules#

Field labels, placeholder text, and menu items should be in sentence case.

Mark the minority of combo boxes in a form as required or optional#

In a single form, mark only the required fields or only the optional fields, depending on whichever is less frequent in the entire form. If most of the combo boxes are optional, only the required fields should be give an asterisk or have labels appended with “(required)”. If most of the combo boxes are required, only the optional fields should be appended with “(optional)”. An asterisk should never be used to note that a combo box is optional.

Use help text to show hints, formatting, and requirements#

The description in the help text is flexible and encompasses a range of guidance. Sometimes this guidance is about what to input, and sometime it’s about how to input. This includes information such as:

• An overall description of the input field
• Hints for what kind of information needs to be input
• Specific formatting examples or requirements

The help text’s message should not simply restate the same information in the label in order to prompt someone to interact with it. Don’t add help text if it isn’t actually relevant or meaningful to a user in order to try to maintain layout continuity with other inputs that require help text.

Don’t use placeholder text#

Putting instructions for how to complete an input, requirements, or any other essential information into placeholder text is not accessible. Once a value is entered, placeholder text is no longer viewable; if someone is using an automatic form filler, they will never get the information in the placeholder text.

Instead of placeholder text, use the help text description to convey requirements or to show any formatting examples that would help user comprehension. If there's placeholder text and help text at the same time, it becomes redundant and distracting, especially if they're communicating the same thing.

Switch help text with error text#

The help text area also displays an error message. When a combo box already includes help text and an error is triggered, the help text is replaced with error text. Once the error is resolved, the help text description reappears below the field.

Since one gets replaced by the other, the language of the help text and error text need to work together to convey the same messaging. Help text explains the requirement or adds supplementary context for how to successfully complete the input. Error text tells a user how to fix the error by re-stating the input requirements or describing the necessary interaction. Make sure that the help text and the error text include the same essential information so that it isn’t lost if one replaces the other (e.g., minimum requirements).

Write error text that shows a solution#

Write error messaging in a human-centered way by guiding a user and showing them a solution — don’t simply state what’s wrong and then leave them guessing as to how to resolve it. Ambiguous error messages can be frustrating and even shame-inducing for users. Also, keep in mind that something that a system may deem an error may not actually be perceived as an error to a user.

Error text should be written in 1-2 short, complete sentences and in a clear and straightforward way. End sentences with a period, and never with an exclamation point. For combo boxes, the nature of the error is often related to something that needs to be fixed for in-line validation, so a helpful tone is most appropriate. For example, if someone were to miss filling out a combo box that asks for them to choose a topic, write the error text like you’re offering a hint or a tip to help guide them to understand what needs to go in the missing field: “Choose at least one topic.”