# What changed in react-dom

> 34 changes in react-dom 19 from its official release notes, upgrade guides and advisories: 4 security, 8 new APIs and options. Each one cited. Sources checked 2026-10-18. HTML: https://unstale.sh/npm/react-dom/

To see which of these apply to a repository, run `npx @unstale/cli init` in it.

## react-dom 19

### Security

- Adds nonce to rendered import maps. (19.3.0) — [release notes](https://github.com/react/react/blob/e8738f0c628b4c321c5ce8077390ba48a8208341/CHANGELOG.md#1930-september-9-2026)
- Enables integration with the Trusted Types API. (19.3.0) — [release notes](https://github.com/react/react/blob/e8738f0c628b4c321c5ce8077390ba48a8208341/CHANGELOG.md#1930-september-9-2026)
- Added more DoS mitigations to Server Actions. (19.0.4, 19.1.5, 19.2.4) — [release notes](https://github.com/react/react/blob/e8738f0c628b4c321c5ce8077390ba48a8208341/CHANGELOG.md#1924-jan-26-2026), [release notes](https://github.com/react/react/blob/e8738f0c628b4c321c5ce8077390ba48a8208341/CHANGELOG.md#1915-jan-26-2026), [release notes](https://github.com/react/react/blob/e8738f0c628b4c321c5ce8077390ba48a8208341/CHANGELOG.md#1904-jan-26-2026)
- Server Components were hardened. (19.0.4, 19.1.5, 19.2.4) — [release notes](https://github.com/react/react/blob/e8738f0c628b4c321c5ce8077390ba48a8208341/CHANGELOG.md#1924-jan-26-2026), [release notes](https://github.com/react/react/blob/e8738f0c628b4c321c5ce8077390ba48a8208341/CHANGELOG.md#1915-jan-26-2026), [release notes](https://github.com/react/react/blob/e8738f0c628b4c321c5ce8077390ba48a8208341/CHANGELOG.md#1904-jan-26-2026)

### New APIs and options

- Adds a react-dom API that resolves in the browser and errors during server rendering; use it inside a Suspense boundary to mark a subtree as browser-only without a recoverable error. (19.3.0) — [release notes](https://github.com/react/react/blob/e8738f0c628b4c321c5ce8077390ba48a8208341/CHANGELOG.md#1930-september-9-2026)
- Recognizes credentialless as a boolean iframe attribute. (19.3.0) — [release notes](https://github.com/react/react/blob/e8738f0c628b4c321c5ce8077390ba48a8208341/CHANGELOG.md#1930-september-9-2026)
- Adds fetchPriority support for module resources. (19.3.0) — [release notes](https://github.com/react/react/blob/e8738f0c628b4c321c5ce8077390ba48a8208341/CHANGELOG.md#1930-september-9-2026)
- Adds support for the maskType SVG prop. (19.3.0) — [release notes](https://github.com/react/react/blob/e8738f0c628b4c321c5ce8077390ba48a8208341/CHANGELOG.md#1930-september-9-2026)
- Adds an option to react-dom/server APIs for observing when a subtree defers to the browser. (19.3.0) — [release notes](https://github.com/react/react/blob/e8738f0c628b4c321c5ce8077390ba48a8208341/CHANGELOG.md#1930-september-9-2026)
- Adds an option for observing subtrees that defer to the browser. (19.3.0) — [release notes](https://github.com/react/react/blob/e8738f0c628b4c321c5ce8077390ba48a8208341/CHANGELOG.md#1930-september-9-2026)
- Adds support for the onFullscreenChange event. (19.3.0) — [release notes](https://github.com/react/react/blob/e8738f0c628b4c321c5ce8077390ba48a8208341/CHANGELOG.md#1930-september-9-2026)
- Adds support for the onFullscreenError event. (19.3.0) — [release notes](https://github.com/react/react/blob/e8738f0c628b4c321c5ce8077390ba48a8208341/CHANGELOG.md#1930-september-9-2026)

### Performance

- Avoids setting innerHTML when its value has not changed. (19.3.0) — [release notes](https://github.com/react/react/blob/e8738f0c628b4c321c5ce8077390ba48a8208341/CHANGELOG.md#1930-september-9-2026)
- Batches updates from resize events until the next frame. (19.3.0) — [release notes](https://github.com/react/react/blob/e8738f0c628b4c321c5ce8077390ba48a8208341/CHANGELOG.md#1930-september-9-2026)
- Tracks explicitly preloaded stylesheets to avoid unnecessary suspension. (19.3.0) — [release notes](https://github.com/react/react/blob/e8738f0c628b4c321c5ce8077390ba48a8208341/CHANGELOG.md#1930-september-9-2026)
- Performance improvements were made to React Server Components. (19.0.6, 19.2.6) — [release notes](https://github.com/react/react/blob/e8738f0c628b4c321c5ce8077390ba48a8208341/CHANGELOG.md#1926-may-6-2026), [release notes](https://github.com/react/react/blob/e8738f0c628b4c321c5ce8077390ba48a8208341/CHANGELOG.md#1906-may-6-2026)

### Behavior and default changes

- Submit events now include submitter, and FormData uses its submitter parameter. (19.3.0) — [release notes](https://github.com/react/react/blob/e8738f0c628b4c321c5ce8077390ba48a8208341/CHANGELOG.md#1930-september-9-2026)
- Transitions render independently instead of being entangled into one render, so a slow transition no longer holds up unrelated ones. (19.3.0) — [release notes](https://github.com/react/react/blob/e8738f0c628b4c321c5ce8077390ba48a8208341/CHANGELOG.md#1930-september-9-2026)
- Type hardening may affect type checking when using React Server Components. (19.0.6) — [release notes](https://github.com/react/react/blob/e8738f0c628b4c321c5ce8077390ba48a8208341/CHANGELOG.md#1906-may-6-2026)

### Fixes and other changes

- For type="number" inputs, defaultValue now matches the behavior of other input types. (19.3.0) — [release notes](https://github.com/react/react/blob/e8738f0c628b4c321c5ce8077390ba48a8208341/CHANGELOG.md#1930-september-9-2026)
- Preserves referrerPolicy in image preload headers. (19.3.0) — [release notes](https://github.com/react/react/blob/e8738f0c628b4c321c5ce8077390ba48a8208341/CHANGELOG.md#1930-september-9-2026)
- Fixes false-positive hydration mismatches on nonce attributes. (19.3.0) — [release notes](https://github.com/react/react/blob/e8738f0c628b4c321c5ce8077390ba48a8208341/CHANGELOG.md#1930-september-9-2026)
- Stops firing onAllReady after the shell has errored. (19.3.0) — [release notes](https://github.com/react/react/blob/e8738f0c628b4c321c5ce8077390ba48a8208341/CHANGELOG.md#1930-september-9-2026)
- Fires onReset when forms are automatically reset. (19.3.0) — [release notes](https://github.com/react/react/blob/e8738f0c628b4c321c5ce8077390ba48a8208341/CHANGELOG.md#1930-september-9-2026)
- Fixes a hang in react-dom/server on Deno. (19.3.0) — [release notes](https://github.com/react/react/blob/e8738f0c628b4c321c5ce8077390ba48a8208341/CHANGELOG.md#1930-september-9-2026)
- Forwards the nonce option when preloading a module. (19.3.0) — [release notes](https://github.com/react/react/blob/e8738f0c628b4c321c5ce8077390ba48a8208341/CHANGELOG.md#1930-september-9-2026)
- Updates HTML parser rules for the new select parser. (19.3.0) — [release notes](https://github.com/react/react/blob/e8738f0c628b4c321c5ce8077390ba48a8208341/CHANGELOG.md#1930-september-9-2026)
- The synthetic toggle event now includes source. (19.3.0) — [release notes](https://github.com/react/react/blob/e8738f0c628b4c321c5ce8077390ba48a8208341/CHANGELOG.md#1930-september-9-2026)
- Fixed missing FormData entries in Server Actions that regressed in 19.2.6. (19.0.7, 19.1.8, 19.2.7) — [release notes](https://github.com/react/react/blob/e8738f0c628b4c321c5ce8077390ba48a8208341/CHANGELOG.md#1927-june-1-2026), [release notes](https://github.com/react/react/blob/e8738f0c628b4c321c5ce8077390ba48a8208341/CHANGELOG.md#1918-june-1-2026), [release notes](https://github.com/react/react/blob/e8738f0c628b4c321c5ce8077390ba48a8208341/CHANGELOG.md#1907-june-1-2026)
- React Server Components add more cycle protections. (19.0.5, 19.1.6, 19.2.5) — [release notes](https://github.com/react/react/blob/e8738f0c628b4c321c5ce8077390ba48a8208341/CHANGELOG.md#1925-march-18-2026), [release notes](https://github.com/react/react/blob/e8738f0c628b4c321c5ce8077390ba48a8208341/CHANGELOG.md#1916-march-18-2026), [release notes](https://github.com/react/react/blob/e8738f0c628b4c321c5ce8077390ba48a8208341/CHANGELOG.md#1905-march-18-2026)
- Extra loop protection was added to React Server Functions. (19.0.3, 19.1.4, 19.2.3) — [release notes](https://github.com/react/react/blob/e8738f0c628b4c321c5ce8077390ba48a8208341/CHANGELOG.md#1923-dec-11-2025), [release notes](https://github.com/react/react/blob/e8738f0c628b4c321c5ce8077390ba48a8208341/CHANGELOG.md#1914-dec-11-2025), [release notes](https://github.com/react/react/blob/e8738f0c628b4c321c5ce8077390ba48a8208341/CHANGELOG.md#1903-dec-11-2025)
- Patched Promise cycles involving Server Functions. (19.0.2, 19.1.3, 19.2.2) — [release notes](https://github.com/react/react/blob/e8738f0c628b4c321c5ce8077390ba48a8208341/CHANGELOG.md#1913-dec-11-2025), [release notes](https://github.com/react/react/blob/e8738f0c628b4c321c5ce8077390ba48a8208341/CHANGELOG.md#1922-dec-11-2025), [release notes](https://github.com/react/react/blob/e8738f0c628b4c321c5ce8077390ba48a8208341/CHANGELOG.md#1902-dec-11-2025)
- React Server Component fixes were brought to Server Actions. (19.0.1, 19.1.2, 19.2.1) — [release notes](https://github.com/react/react/blob/e8738f0c628b4c321c5ce8077390ba48a8208341/CHANGELOG.md#1921-dec-3-2025), [release notes](https://github.com/react/react/blob/e8738f0c628b4c321c5ce8077390ba48a8208341/CHANGELOG.md#1912-dec-3-2025), [release notes](https://github.com/react/react/blob/e8738f0c628b4c321c5ce8077390ba48a8208341/CHANGELOG.md#1901-dec-3-2025)
- Patched toString behavior on Server Functions. (19.1.3) — [release notes](https://github.com/react/react/blob/e8738f0c628b4c321c5ce8077390ba48a8208341/CHANGELOG.md#1913-dec-11-2025)