microsoft / microsoft/TypeScript

`autocapitalize` type is incorrect according to MDN

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@RyanCavanaugh is already working on this.

Since Sep 19, 2026.

  • #64329 by @copilot-swe-agent — open
Bug Domain: lib.d.ts Help Wanted Needs Human Review
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Description

lib Update Request

In lib/dom.d.ts

https://github.com/microsoft/TypeScript/blob/main/src/lib/dom.generated.d.ts#L9992

the type for HTMLElement.autocapitalize is incorrectly typed as string. According to the MDN article, the autocapitalize attribute/property can only be set to certain keywords.

Therefore, the internal lib dom type should be:

autocapitalize: 'off' | 'none' | 'on' | 'sentences' | 'words' | 'characters';

Sample Code

This issue affects proper typing in web components that extend HTMLElement that attempt to correctly type autocapitalize. TS errors because string and a union type are not compatible. Every reference to a web component class extending HTMLElement with a proper type for autocapitalize errors incorrectly.

Documentation Link

MDN article on autocapitalize

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