Best Practices for Designing UI Inputs

Encountering an error message is often a frustrating experience for users. It signifies that an issue has occurred, and users must invest additional effort to proceed with their task. To lessen this frustration, offer a helpful and constructive explanation about the problem and provide clear instructions on how users can resolve it promptly.

When designing error messages, ensure that they are easily scannable at a quick glance. Ideally, aim to keep the message within a single line to maximize visibility and avoid overwhelming users with too much text.

If the message cannot fit within one line without compromising clarity, it's acceptable to extend it to a second line. However, ensure that the message remains complete and coherent without any truncation, as cutting off essential information can lead to further user confusion.

Selection controls allow us to pick an item or a few items and move on with a task. Dropdown menus can be good choices for longer lists — they save space and don't overwhelm users. But for shorter lists with up to 5 options, they're unnecessarily complicated.

Radio buttons work much better in cases when you need to make a single selection, as they're more straightforward and require fewer clicks. If you allow users to make multiple choices, consider using checkboxes.

There are nearly 200 countries worldwide, and finding yours in the dropdown list can be a pain, even when they're in alphabetical order. To avoid frustration, provide search functionality to filter the options as users type — it's called auto-suggest. In contrast to dropdown menus that require users to scroll endlessly, the functionality finds matches and immediately presents them as users type in an input.

Country lists aren't the only inputs that benefit from auto-suggest search. Consider using this functionality any time users need to select from a long list of options.

Fields with incremental search show all results that match what users are typing as they type. Use a different font style to differentiate between the matching characters a user has typed and the rest of the suggested word or phrase. Use bold vs. regular weight to differentiate between the matching and suggested parts.

Placing error messages near input fields improves usability. Users quickly associate the error with the specific field, reducing frustration and speeding up correction. The best placement is to the right of the input or directly below it.^[1]

Errors placed above the input can be missed, especially in forms with multiple fields. Errors on the left disrupt the reading flow in left-to-right languages. Messages should be visually distinct but not intrusive.

For accessibility, errors should be programmatically linked to inputs using ARIA attributes. This ensures screen readers announce them properly to those using such assistive technology.

There are plenty of ways users can input a phone number. Instead of forcing users to type in the desired format, you can use a phone mask and prevent errors.^[2] It allows users to enter the phone in whatever way they like and then auto-format the number into a standard format for your system's purposes.

Remember that input masks aren't placeholders. They appear only on focus and as users start typing. Placeholders, in fact, can be remarkably misleading, looking like automatic defaults and making users think the data is already filled.

Considering the fact that users in different countries format dates differently, input masks are really essential. For example, most of the world uses the DD/MM/YYYY format, while the USA uses MM/DD/YYYY instead. Adding a date mask helps avoid confusion and ensures that dates are uniform.

When your product is accessible to users around the world, it's important to inform those who typically use a different currency in their daily transactions about the currency your website or service accepts. This information becomes particularly relevant when users need to convert currency or filter a list of items, such as on an e-commerce site. While it may seem like a small detail, providing a clear currency label serves as a reassuring guide for users on their journey and subtly contributes to building trust.

Any time users are making a purchase, remove as many potential stumbling blocks as possible. The more a user has to think about the process, the more chances they have to change their mind entirely.

One effective way to reduce these uncertainties and enhance the user experience is by incorporating a credit card input mask into your payment forms. This input mask serves as a visual guide, making it easier for users to enter their credit card information accurately. It ensures that the information is formatted correctly, minimizing the risk of errors, and consequently reducing potential frustrations or complications during the checkout process. 

When users fill up forms while making a purchase or booking a flight ticket, they want to stay informed about what's happening in the system.

To make the error inputs easy to notice and understand:

• Indicate error inputs using a prominent, contrasting color (usually red) and a relevant icon. 
• Politely describe what happened and what users should do to fix the problem. 
• Apply real-time, inline validation rather than submit-time modals. The latter breaks the flow and distracts users. Errors that appear immediately allow users to correct their answers before moving on.^[3]