npm / browserslist
browserslist
What changed in browserslist 4, from its official release notes, upgrade guides and advisories. Sources checked 2026-10-17.
1 breaking4 security1 new APIs and options2 performance2 behavior and defaults8 fixes and other
See which of these apply to your code, ranked, in your agent:
npx @unstale/cli initbrowserslist 418 changes
Breaking changes 1
Removed the Baseline warning because it has its own warning.
Security 4
Fixed config name loading protection on Windows.
Browserslist: Unbounded memory growth (no cache eviction) via distinct query results, leading to eventual OOM
Browserslist: Uncaught crash / prototype write via untrusted browserslist-stats.json custom stats (normalizeStats)
Fixes prototype pollution.
New APIs and options 1
Added the BROWSERSLIST_TRACE_WARNING environment variable.
Performance 2
Improves
orparsing performance.Parsing performance was improved.
Behavior and default changes 2
Browserslist’s Firefox ESR data was updated, which may change the browser versions selected by matching queries.
Queries can now continue across lines and array entries, allowing multiline query configuration.
Fixes and other changes 8
Fixed ignoring null usage in cover X in Y queries.
Fixed case-insensitive negation queries.
Fixed percentage and supports queries case-insensitive.
Fixed
including kaiosin baseline queries.Fixed Electron version queries.
Fixed
>and>=queries.Fixed the SyntaxError regression introduced in 4.28.3.
Baseline queries are now case-insensitive.