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MUI X v9.0: Tree View, Date Pickers

José Freitas

@joserodolfofreitas
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In v9, we focused: large trees that stay fast and predictable, and pickers that behave well on keyboard, in forms, and next to other controls, with locale and adapter coverage that stays aligned with all the other components.

For line‑item changes, follow the MUI X releases timeline.

This new major is part of a coordinated effort across the entire product suite; for a complete look at the MUI ecosystem changes, check out the Introducing Material UI and MUI X v9 blog post.

Table of contents

Date and Time Pickers

Pickers in v9 continue the keyboard‑first calendar work: move through day, month, and year without treating pointer interaction as mandatory. fieldRef stabilizes with clearValue, which matters in long forms, filters, and anywhere "reset this field" must be reliable.

We also smoothed focus when dismissing the popover so click‑away is less likely to strand focus on the wrong control, especially near dialogs, drawers, and embedded grid filters. Locales and adapters expand (for example, thTH in step with the Data Grid, and AdapterDayjsBuddhist for non‑Gregorian cases); if you use range pickers across zones, re‑validate edge cases after upgrading.

Some cleanup changes are also important in v9:

  • #21966: removes enableAccessibleFieldDOMStructure; the accessible field DOM is now the only supported mode, with codemod support.
  • #21739: removes PickersDay and promotes PickerDay2 as the default day component API.

The Date and Time Pickers docs (including migration notes) remain the source of truth for API deltas as v9 stabilizes.

Tree View

Rich Tree View Pro in v9 ships virtualization on by default, with an explicit opt‑out when you need a non‑virtualized layout. That shift comes with practical defaults (for example, row height, set itemHeight when content differs). Also, v9 changed Rich Tree View Pro events from a nested tree shape to a flat list (called out in the v9 alpha release notes), which is required to add support for virtualization.

API and styling hygiene matter too: older model and ref hooks are replaced by the richer variants (useRichTreeViewApiRef, useSimpleTreeViewApiRef, useRichTreeViewProApiRef), TreeViewBaseItem is removed in favor of documented model shapes, and state tokens on treeItemClasses that encoded expanded/selected styling are dropped in favor of data-* attributes you can target in CSS.

If you maintain custom themes or imperative code against trees, budget time to revisit refs, virtualization assumptions, and selectors that depended on the old classes.

Full API notes live in the Tree View documentation.

Migration guides

For a complete list of breaking changes and codemod steps, use the dedicated migration guides:

Further reading

We want your feedback

Your input drives our direction. Join our GitHub communities today to share your insights, report issues, and help shape the future. Visit MUI X on GitHub.