Selection list for selected countries
(Figure 2), which has more than 100 options, and it is impossible for users to have a quick overview of the entire list, and it is difficult to find the desired option in a short time.
I myself often can't find where "America" is! Usually "United States" as a more Country Email List popular option will be placed at the top of the list. However, if some lists are alphabetically sorted, countries like "Afghanistan" will be placed at the front of the list (starting with an A in English), while the corresponding "United States" and "UAE" will be placed at the end of the list together ( English all start with U) - so as a user, I often have to think about the arrangement logic of this selection menu before looking for options.
When users know exactly which option they need to find, consider using an input box with auto-fill functionality instead of a selection menu.
Still taking "select country" as an example, from a programming point of view, you can try to automatically locate the user's location, or automatically give the closest guess option based on the first word entered by the user in real time (Figure 3).
Figure 3: Entering "United" automatically matches possible options
Quick summary: When there are more than 15 options, instead of using the select menu, consider using input boxes that allow direct user input or autofill.
Mistake 2: Too few options
If you have less than 7 options and you still use the drop-down selection list, then you hide the information that can actually be displayed directly, in other words, the user needs to make an extra click to see all the options.
Figure 4: Dropdown with only 2 options
In such cases with fewer options, it would be better to use radio buttons (Figure 5). This way, users can immediately see that there are several options, and quickly know what those options are, rather than needing to click again to see the option information.
Figure 5: When there are only 2 options, display all options directly
Quick summary: If there are less than 7 options, then just use the radio button.
2. Select menus and tabs
All input forms need to have labels that prompt the user how they should select the input. The same is true for select menus, you should give the user some helpful hints, rather than simply labeling a "no option" or "please select".
The prompt label should quickly and directly tell the user "what" they should choose, and hint to the user that he is about to choose among "what" options (Figure 6).