# Material UI v9.1.0

- Product: Material UI (https://whatsnew.fyi/product/material-ui)
- Vendor: MUI
- Date: 2026-06-08
- Version: v9.1.0
- Original notes: https://github.com/mui/material-ui/releases/tag/v9.1.0
- Permalink: https://whatsnew.fyi/product/material-ui/releases/v9.1.0

What's New is an index, not a publisher: every entry below links to the vendor's own release notes, which are the authoritative source. Entries are labelled where they are hand-curated sample data, pre-releases, or drawn from a secondary source such as a developer blog.

Reuse: the summaries, labels and curation here are © What's New. Quote freely with attribution and a link back; wholesale republication of the corpus is not permitted — terms: https://whatsnew.fyi/terms. The vendors' own release notes remain their publishers'.

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- **added** — Support for the prefers-reduced-motion setting
- **added** — Improved support for Windows High Contrast mode with the enhanceHighContrast theme wrapper
- **added** — Custom Transition component support in transitions
- **changed** — Badge now uses inline CSS variables for anchorOrigin and overlap positioning
- **changed** — StepConnector is now included inside Step element
- **changed** — Stepper now has proper support for vertical alternativeLabel
- **changed** — Select now allows spacebar to select elements
- **changed** — Select now supports typeahead when closed
- **changed** — StepButton now chooses higher contrast ripple color for dark mode focus
- **fixed** — Autocomplete now clears highlight when mouse leaves popup
- **fixed** — Autocomplete freeSolo controlled values no longer cleared by initial null
- **fixed** — Autocomplete item removal when it receives focus from VoiceOver before using Backspace
- **fixed** — Autocomplete guard against null inputRef during unmount
- **fixed** — Button customized flex gap styles
- **fixed** — Dialog unwanted DialogPaper focus ring
- **fixed** — Focus trap incorrect tab order when tabIndex is greater than or equal to 1
- **fixed** — Progress show runtime errors only once
- **fixed** — Tabs React 18 roving tabindex and dedupe invalid-value warning
- **fixed** — Timeline item extra ::before spacing when TimelineOppositeContent is present
- **fixed** — Tooltip prevent stuck-open tooltip when child becomes disabled
- **security** — Prevent prototype pollution in fastDeepAssign

A big thanks to the 15 contributors who made this release possible. Here are some highlights ✨:

- ⚙️ Support for the [prefers-reduced-motion](https://mui.com/material-ui/transitions/#reduced-motion) setting.
- ♿️ Improved support for Windows High Contrast mode with the [enhanceHighContrast](https://mui.com/material-ui/customization/palette/#windows-high-contrast-mode) theme wrapper.

###### `@mui/material@9.1.0`

- [autocomplete] Enable clearing highlight when mouse leaves popup (#48354) @mj12albert
- [autocomplete] Fix `freeSolo` controlled values cleared by initial `null` (#48611) @mj12albert
- [autocomplete] Fix item removal when it receives focus from VoiceOver before using Backspace (#48572) @silviuaavram
- [autocomplete] Fix `resetHighlightOnMouseLeave` JSdoc (#48536) @mj12albert
- [autocomplete] Guard against null inputRef during unmount (#48617) @noam3127
- [badge] Add `aria-hidden` to badge content and polish docs demos (#48471) @mj12albert
- [badge] Use inline CSS variables for anchorOrigin/overlap positioning (#48549) @siriwatknp
- [button] Fix customized flex gap styles (#48542) @mj12albert
- [dialog] Fix unwanted `DialogPaper` focus ring (#48535) @mj12albert
- [focus trap] Fix incorrect tab order when `tabIndex >= 1` (#48546) @mj12albert
- [progress] Show runtime errors only once (#48591) @silviuaavram
- [select] Allow spacebar to select elements (#48615) @silviuaavram
- [select] Support typeahead when closed (#48563) @mj12albert
- [step button] Choose higher contrast ripple color for dark mode focus (#48612) @silviuaavram
- [stepper] Include StepConnector inside Step element (#48492) @silviuaavram
- [stepper] Proper support for vertical alternativeLabel (#48485) @silviuaavram
- [tabs] Fix React 18 roving tabindex and dedupe invalid-value warning (#48605) @Janpot
- [theme] Add HighContrast theme enhancer (#48319) @silviuaavram
- [timeline item] Fix extra ::before spacing when TimelineOppositeContent is present (#46663) @tyalau
- [tooltip] Prevent stuck-open tooltip when child becomes disabled (#48606) @Janpot
- [transitions] Custom `Transition` component (#48325) @mj12albert
- [transitions] Support `prefers-reduced-motion` (#48357) @mj12albert

###### `@mui/utils@9.1.0`

- [utils] Prevent prototype pollution in fastDeepAssign (#48580) @Janpot

###### Docs

- [docs] Add function `slotProps` documentation (#48574) @mj12albert
- [docs] Clarify styled-components version compatibility (#48533) @nightt5879
- [docs] Fix broken URLs (#48520) @oliviertassinari
- [docs] Fix invalid JSON in Zed MCP setup example (#48490) @pavan-sh
- [docs] Mention release version for enhanceHighContrast (#48609) @silviuaavram
- [docs] Remove outdated MUI X v8 notification (#48600) @cherniavskii
- [docs] Remove redundant enhanceHighContrast information (#48632) @silviuaavram
- [docs-infra] Decrease loaded bundle size on docs (#48584) @brijeshb42
- [docs-infra] Drop multi-locale plumbing from API pages (#48370) @brijeshb42
- [docs-infra] Fix Cookie banner heading (#48529) @oliviertassinari
- [docs-infra] Infinitely cache all static assets (#48627) @brijeshb42
- [docs-infra] Remove outdated noSEOadvantage entries (#48527) @oliviertassinari
- [docs-infra] Restore build-only invariant throws via `NEXT_RUNTIME` guard (#48475) @Janpot
- [docs-infra] Test HTML validation in broken links checker (#48088) @Janpot
- [docs][icons] Fix Font Awesome Chip demo in dark mode (#48576) @siriwatknp
- [docs][icons] Remove redundant font awesome demo (#48493) @ZeeshanTamboli
- [docs][modal] Add nested modal guidance (#46507) @JakeSaterlay
- [docs][stepper] Fix focus management in examples (#48494) @silviuaavram

###### Core

- Eslint markdown (#48371) @Janpot
- [agents] Fix some docs links (#48561) @silviuaavram
- [blog] Copy editing improvement on v9 announcement blog posts (#48543) @joserodolfofreitas
- [code-infra] Cleanup unused jss packages (#48590) @brijeshb42
- [code-infra] Collapse canary workf

_[Truncated at 4000 characters — full notes: https://github.com/mui/material-ui/releases/tag/v9.1.0]_