HTML `<datalist>`

Description

As the web's native combobox, <input list> combined with <datalist> behaves inconsistently across browser engines and platforms. All modern browsers implement <datalist>, minus a few areas of support on Firefox, but vary in styling and behavior.

The proposed scope for this investigation:

• Popup rendering
  • Styling and positioning consistency
  • Desktop and mobile keyboard-suggestions displays
• Filtering behavior
  • How options are filtered against value
  • Case matching differences
• Display consistency when <option> text and value differ
• Affordance styling (the popup indicator icon)
  • Does this follow same convention of <select>?
• Browser engine consistency
  • Working as more than a text box
  • Options availability in landscape mode
  • Mobile landscape behavior
• A11y - roles and names as exposed to screen readers, keyboard navigation, escape behavior, and voice-control
• A11y - Page Zoom and text styling in popup
• A11y - AT inconsistencies

Rationale

Many of the identified issues are listed in Adrian Roselli's "Under-Engineered Comboboxen".

Web developer usage from State of HTML survey is very low year after year

APG provides custom combobox patterns as a good informative pattern but shouldn't be treated as normative. Extending these patterns can and does introduce new a11y issues.

Investigation Roadmap

Specification

https://html.spec.whatwg.org/multipage/form-elements.html#the-datalist-element

Web platform

https://web-platform-dx.github.io/web-features-explorer/features/datalist/
https://wpt.fyi/results/html/semantics/forms/the-datalist-element/datalistoptions.html?label=experimental&label=master&aligned&q=datalist

Test links

https://github.com/web-platform-tests/wpt/tree/master/html/semantics/forms/the-datalist-element

Adoption of <datalist> is low, according to Chrome Platform Status.

Start with the HTML specification's datalist section and the WPT tests under html/semantics/forms/the-datalist-element, especially datalistoptions.html. Compare the documented behavior with the wpt.fyi results and the browser/platform areas listed in the investigation scope; done requires a focused set of findings or test gaps rather than a single code change.