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conformance · v145

v145 · customizable-select-listbox — conformance probe

10 assertions drawn from the spec. Each is a single contract the spec text makes. Pass/fail reflects what this browser executed; blocked means the contract was not run because it needs user mediation, hardware, or another unavailable precondition. Open the page in Chrome stable / canary / Firefox / Safari to compare.

browser: spec: https://html.spec.whatwg.org/multipage/form-elements.html#the-select-element chromestatus: #6222145025867776 generated 2026-06-04T00:11:07Z by codex-listbox-shape-scope-repair
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pass
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fail
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blocked
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id contract kind verdict detail
select-element-exists HTMLSelectElement is exposed — the foundation customizable listbox extends. exists
select-multiple-supported The HTML multiple attribute on <select> is reflected as a property, the opt-in for multi-select listbox rendering. script
select-size-supported The HTML size attribute on <select> is reflected as a number property, the other opt-in to listbox rendering. script
appearance-base-select-supported appearance: base-select is supported in CSS — the toggle that activates the customizable listbox UI. spec ↗ css-supports
option-element-exists HTMLOptionElement is exposed — listbox renders its options through this interface. exists
option-selected-roundtrip Setting selected on an option round-trips — the basic state mechanic listbox depends on for selection rendering. script
multi-listbox-shape-is-multiple-size-greater-than-one The Chrome 145 customizable listbox path can be expressed as a multiple select with a visible size greater than one. spec ↗ script
single-listbox-shape-is-size-greater-than-one The Chrome 145 customizable listbox path also includes single-select listboxes created with size greater than one. spec ↗ script
multi-popup-shape-is-multiple-size-one A multiple select with size=1 is the multi-select popup shape, which ChromeStatus says is outside this Chrome 145 listbox feature. spec ↗ script
option-rich-markup-is-retained-in-dom Rich child markup inside option remains in the DOM for customizable select listbox rendering. spec ↗ script