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name: react18-dep-compatibility description: 'React 18.3.1 and React 19 dependency compatibility matrix.'

React Dependency Compatibility Matrix

Minimum versions required for React 18.3.1 and React 19 compatibility.

Use this skill whenever checking whether a dependency supports a target React version, resolving peer dependency conflicts, deciding whether to upgrade or use legacy-peer-deps, or assessing the risk of a react-router v5 to v6 migration.

Review this matrix before running npm install during a React upgrade and before accepting an npm dependency conflict resolution, especially where concurrent mode compatibility may be affected.

Core Upgrade Targets

| Package | React 17 (current) | React 18.3.1 (min) | React 19 (min) | Notes | |---|---|---|---|---| | react | 17.x | 18.3.1 | 19.0.0 | Pin exactly to 18.3.1 for the R18 orchestra | | react-dom | 17.x | 18.3.1 | 19.0.0 | Must match react version exactly |

Testing Libraries

| Package | React 18 Min | React 19 Min | Notes | |---|---|---|---| | @testing-library/react | 14.0.0 | 16.0.0 | RTL 13 uses ReactDOM.render internally - broken in R18 | | @testing-library/jest-dom | 6.0.0 | 6.0.0 | v5 works but v6 has React 18 matcher updates | | @testing-library/user-event | 14.0.0 | 14.0.0 | v13 is sync, v14 is async - API change required | | jest | 27.x | 27.x | jest 27+ with jsdom 16+ for React 18 | | jest-environment-jsdom | 27.x | 27.x | Must match jest version |

Apollo Client

| Package | React 18 Min | React 19 Min | Notes | |---|---|---|---| | @apollo/client | 3.8.0 | 3.11.0 | 3.8 adds useSyncExternalStore for concurrent mode | | graphql | 15.x | 16.x | Apollo 3.8+ peer requires graphql 15 or 16 |

Read references/apollo-details.md for concurrent mode issues and MockedProvider changes.

Emotion

| Package | React 18 Min | React 19 Min | Notes | |---|---|---|---| | @emotion/react | 11.10.0 | 11.13.0 | 11.10 adds React 18 concurrent mode support | | @emotion/styled | 11.10.0 | 11.13.0 | Must match @emotion/react version | | @emotion/cache | 11.10.0 | 11.13.0 | If used directly |

React Router

| Package | React 18 Min | React 19 Min | Notes | |---|---|---|---| | react-router-dom | v6.0.0 | v6.8.0 | v5 → v6 is a breaking migration - see details below | | react-router-dom v5 | 5.3.4 (workaround) | ❌ Not supported | See legacy peer deps note |

react-router v5 → v6 is a SEPARATE migration sprint. Read references/router-migration.md.

Redux

| Package | React 18 Min | React 19 Min | Notes | |---|---|---|---| | react-redux | 8.0.0 | 9.0.0 | v7 works on R18 legacy root only - breaks on concurrent mode | | redux | 4.x | 5.x | Redux itself is framework-agnostic - react-redux version matters | | @reduxjs/toolkit | 1.9.0 | 2.0.0 | RTK 1.9 tested against React 18 |

Other Common Packages

| Package | React 18 Min | React 19 Min | Notes | |---|---|---|---| | react-query / @tanstack/react-query | 4.0.0 | 5.0.0 | v3 doesn't support concurrent mode | | react-hook-form | 7.0.0 | 7.43.0 | v6 has concurrent mode issues | | formik | 2.2.9 | 2.4.0 | v2.2.9 patched for React 18 | | react-select | 5.0.0 | 5.8.0 | v4 has peer dep conflicts with R18 | | react-datepicker | 4.8.0 | 6.0.0 | v4.8+ added React 18 support | | react-dnd | 16.0.0 | 16.0.0 | v15 and below have R18 concurrent mode issues | | prop-types | any | any | Standalone - unaffected by React version |

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Conflict Resolution Decision Tree

npm ls shows peer conflict for package X
         │
         ▼
Does package X have a version that supports React 18?
  YES → npm install X@[min-compatible-version]
  NO  ↓
         │
Is the package critical to the app?
  YES → check GitHub issues for React 18 branch/fork
      → check if maintainer has a PR open
      → last resort: --legacy-peer-deps (document why)
  NO  → consider removing the package

--legacy-peer-deps Rules

Only use --legacy-peer-deps when:

• The package has no React 18 compatible release
• The package is actively maintained (not abandoned)
• The conflict is only a peer dep declaration mismatch (not actual API incompatibility)

Document every --legacy-peer-deps usage in a comment at the top of package.json or in a MIGRATION.md file explaining why it was necessary.