Is Vitest 5 Faster Than Vitest 4? We Timed It

Vitest 5 upgrade decision with ShopperCove timing: 20-file forks suite median ~512 ms on 5.0.3 vs ~547 ms on 4.1.10 (Node 22.20.0). Engines require Node 22.12+ and Vite 6.4+. clearMocks defaults true. No affiliate.

5 October 20264 min read

Summary

Vitest 5 is worth upgrading to if you already run Node 22.12+ (or 24/26) and Vite 6.4+: on the same 20-file, 40-test forks suite, Vitest 5.0.3 had a median of about 512 ms against about 547 ms on 4.1.10 (about 6% faster). Stay on 4 until you can raise Node and Vite, and check tests that rely on mock call history, because clearMocks now defaults to true.

Should you upgrade to Vitest 5?

Yes if you already run Node 22.12+ (or 24 / 26) and Vite 6.4+, want the Vitest 5 performance work (shared Vite server for inline projects, stable fsModuleCache, faster vm pools / Browser Mode), and can absorb migration defaults like clearMocks: true. Wait if you are still on Node 20, cannot bump Vite yet, or your suite relies on mock call history leaking across tests without an explicit reset.

npm’s current line is vitest@5.0.3 (modified 2026-09-30T11:30:42Z / ~17:00 IST). The 5.0.0 blog line landed 3 Sep 2026.

What I measured (ShopperCove box)

Identical fixtures: twenty utilN.ts + utilN.test.ts pairs, vitest.config.ts with pool: 'forks', no isolation change, no coverage.

Runner	Node	Run 1	Run 2	Run 3	Median
Vitest 4.1.10 + Vite 6.4.0	22.20.0	547 ms	598 ms	530 ms	~547 ms
Vitest 5.0.3 + Vite 6.4.0	22.20.0	528 ms	512 ms	482 ms	~512 ms

On this tiny suite the win is modest (~6%). Vitest’s own benchmarks write-up shows much larger drops on heavier apps (for example their deps-heavy vmThreads cell 1.59 s → 0.74 s, about −53%). Treat our number as a local smoke cost, not a claim that every monorepo will see 50% cuts.

package.json engines on 5.0.3: node: '^22.12.0 \|\| ^24.0.0 \|\| >=26.0.0'. Peer vite: ^6.4.0 \|\| ^7.0.0 \|\| ^8.0.0. On this box Node 20.19.2 still executed vitest run for 5.0.3 (40/40 pass), but that is unsupported—migrate Node before you rely on 5 in CI.

clearMocks default (confirmed)

I ran a two-test module where a module-scoped vi.fn() is called in test A, then asserted to have 0 calls at the start of test B. On 5.0.3 that assertion passed—matching the migration note that clearMocks defaults to true (vi.clearAllMocks() before each test). If you depended on cross-test call history, set clearMocks: false or move spies into beforeEach.

Breaking-change checklist (skim before `pnpm up`)

Node ≥ 22.12 and Vite ≥ 6.4 (Yarn users: add vite explicitly—it is a peer now).
clearMocks: true by default—fix order-dependent mock history.
Unawaited .resolves / .rejects / toMatchFileSnapshot fail the test (no more soft warn).
vi.mock / vi.hoisted outside top level now throw.
Inline projects inherit root config (extends defaults true) and may share the Vite server.
Browser / reporter artifact paths moved under .vitest/; UI needs the printed auth token.
Bench API: bench is a test-context fixture, not a top-level import.

Official detail: Vitest 5 blog and Migration Guide.

Bottom line

Should you upgrade? If you already meet the Node/Vite floor, Vitest 5 is the supported line—our 20-file median ~512 ms vs ~547 ms is a small green light, and the real wins show up on larger / vm / browser suites in Vitest’s own tables. If you are on Node 20, upgrade Node first; do not treat an accidental green run on unsupported Node as production-ready. No affiliate.

FAQ

Is Vitest 5 faster than Vitest 4?

On this small 20-file suite, slightly: median ~512 ms on 5.0.3 vs ~547 ms on 4.1.10. Vitest's own benchmarks show bigger drops on heavier projects, such as 1.59 s to 0.74 s in one vmThreads case.

What Node version does Vitest 5 need?

Node ^22.12.0, ^24.0.0 or >=26.0.0, with Vite ^6.4.0, ^7 or ^8 as a peer. It ran on Node 20.19.2 in this test, but that setup is unsupported.

What breaks when upgrading to Vitest 5?

clearMocks defaults to true, unawaited .resolves/.rejects and toMatchFileSnapshot now fail tests, vi.mock and vi.hoisted outside top level throw, and bench becomes a test-context fixture.

Sources

vitest unit testing node.js vite performance migration testing tools

Lab evidence

What I found running this

Sources read 5 Oct 2026 evening (Asia/Calcutta): vitest.dev/blog/vitest-5.html (3 Sep 2026); vitest.dev/guide/migration.html (Node >=22.12, Vite >=6.4; clearMocks default true; unawaited async asserts fail). npm vitest latest=5.0.3 time.modified 2026-09-30T11:30:42.795Z (~17:00 IST); 5.0.0 published 2026-09-03T12:24:30.312Z. package engines node '^22.12.0 || ^24.0.0 || >=26.0.0'; peer vite '^6.4.0 || ^7.0.0 || ^8.0.0'. Hands-on on box Node 22.20.0: identical 20-file/40-test forks suite — Vitest 4.1.10 (pnpm) warm medians 547/598/530 ms → median ~547 ms; Vitest 5.0.3 warm 528/512/482 ms → median ~512 ms. clearMocks fixture: module-scoped vi.fn() call count cleared between tests on 5.0.3 (2/2 pass). Node 20.19.2 still ran vitest 5.0.3 (unsupported). No ShopperCove production suite changed. No affiliate.

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