3.51.0 - 2026.10.19

• Changes v3.50.0...v3.51.0 (62 commits)
• Iterator chunking proposal:
  • Built-ins:
    • Iterator.prototype.chunks
    • Iterator.prototype.windows
  • Moved to stable ES, September 2026 TC39 meeting
  • Added es. namespace modules, /es/ and /stable/ namespace entries
• Iterator includes proposal:
  • Built-in:
    • Iterator.prototype.includes
  • Moved to stable ES, September 2026 TC39 meeting
  • Added es. namespace module, /es/ and /stable/ namespace entries
• Iterator join proposal:
  • Built-in:
    • Iterator.prototype.join
  • Moved to stable ES, September 2026 TC39 meeting
  • Added es. namespace module, /es/ and /stable/ namespace entries
• Added detection / fix of Math.sumPrecise negative numbers handling WebKit bug
• Added detection / fix of Math.sumPrecise V8 bugs with modified prototypes of arrays and array iterators
• Added detection / fix of RegExp.escape code points handling WebKit bug
• Added missed detection of imprecise native Math.asinh in V8 < 5.4 and Rhino
• Added missed detection of imprecise native Math.cbrt in FF < 48 and engines that use glibc cbrt
• Fixed Promise.{ allKeyed, allSettledKeyed } algorithm for sync promises
• Compat data improvements:
  • Iterator.{ zip, zipKeyed } marked as shipped in V8 ~ Chrome 153
  • Iterator.prototype.includes marked as shipped in V8 ~ Chrome 154
  • Iterator.prototype.join marked as shipped in V8 ~ Chrome 153
  • Promise.{ allKeyed, allSettledKeyed } marked as shipped in FF155
  • Iterator.prototype.{ drop, take } marked as properly supported with tc39/ecma262/#3776 from FF158
  • Iterator.{ zip, zipKeyed } marked as shipped in Bun 1.4.0
  • Iterator.prototype.{ chunks, windows } marked as shipped in Bun 1.4.0
  • Iterator.prototype.join marked as shipped in Bun 1.4.0
  • Because of a Math.sumPrecise negative numbers handling WebKit bug, this method is marked as not supported in Safari and Bun
  • Because of Math.sumPrecise V8 bugs (see above), this method is marked as not supported in Chrome -> all other V8 engines
  • RegExp.escape code points handling WebKit bug:
    • Marked as still not fixed in stable Safari
    • Marked as fixed in Bun 1.4.3
  • Because of imprecision (see above), Math.asinh is marked as supported from V8 ~ Chrome 54 and as not supported in Rhino, Math.cbrt - from FF48
  • Added Node 27.0 compat data mapping
  • Updated Electron 45 and added 46 compat data mapping
  • Added Samsung Browser 31 compat data mapping
  • Added Opera for Android 101 and 102 compat data mapping

3.50.0 - 2026.08.05

• Changes v3.49.0...v3.50.0 (138 commits)
• Joint iteration proposal:
  • Built-ins:
    • Iterator.zip
    • Iterator.zipKeyed
  • Moved to stable ES, May 2026 TC39 meeting
  • Added es. namespace modules, /es/ and /stable/ namespace entries
• Iterator chunking proposal:
  • Built-ins:
    • Iterator.prototype.chunks
    • Iterator.prototype.windows
  • Throw a TypeError instead of RangeError on non-integer number chunkSize / windowSize, following tc39/proposal-iterator-chunking/#30
  • Moved to stage 3, May 2026 TC39 meeting
  • Added /actual/ namespace entries, unconditional forced replacement changed to feature detection
• Added Iterator includes stage 3 proposal:
  • Added built-in:
    • Iterator.prototype.includes
• Added Iterator join stage 3 proposal:
  • Added built-in:
    • Iterator.prototype.join
• Added Await dictionary of Promises stage 3 proposal:
  • Added built-ins:
    • Promise.allKeyed
    • Promise.allSettledKeyed
• Throw a RangeError on finite unsafe integer limit in Iterator.prototype.{ drop, take }, following tc39/ecma262/#3776
• Use PromiseResolve semantics in Promise.try, following tc39/ecma262/#3883
• Added detection of missed Webkit ~ Safari < 26.2 Iterator.prototype.flatMap bug case, #1538
• Deno 2.9+ replaces Object.prototype.__proto__ instead of removing it, so the feature detection updated
• Fixed JSON.stringify polyfill with an array replacer - keys order now follows the replacer, inherited and non-enumerable properties are no longer ignored, #1539
• Make URL / URLSearchParams parsing a little more correct (char sets, percent coding, etc)
• Ensure opaque paths always roundtrip in URL polyfill (still without adding to feature detection), whatwg/url#844
• Fix URL#toJSON when URL#toString is reassigned after core-js is imported
• Fixed possible crash on some keys in Symbol.for
• Some get-iterator / get-iterator-method fixes
• Fixed String.prototype.{ match, search } polyfills conversion order
• Added missed MAX_SAFE_INTEGER excess check in Array.from and { Map, Object }.groupBy polyfills
• Improved the way of inner iterators cleaning in iterator helpers
• Improved accuracy of Math.{ asinh, cbrt, log1p } polyfills with big and small values
• Improved performance of Uint8Array base64 methods
• Improved performance of escape
• Slight performance improvement for engines with native Array.prototype.fill on ArrayBuffer constructor and %TypedArray%.prototype.fill
• Clarify supported Node versions in package.json of some missed packages (just to satisfy publint)
• Compat data improvements:
  • Following tc39/ecma262/#3776, Iterator.prototype.{ drop, take } properly supported from:
    • V8 ~ Chrome 150
    • Safari 27.0
    • Bun 1.4.0
  • Following tc39/ecma262/#3883, Promise.try marked as not properly supported in all engines
  • Iterator.prototype.{ chunks, windows } marked as shipped in FF154
  • Iterator.prototype.includes marked as shipped in FF154
  • Iterator.prototype.includes marked as shipped in Bun 1.4.0
  • Iterator.prototype.join marked as shipped in FF154
  • Array.prototype.includes WebKit bug marked as fixed in:
    • Safari 27.0
    • Bun 1.3.12
  • queueMicrotask Bun bug marked as fixed in Bun 1.4.0
  • Added Node 26.0 compat data mapping
  • Added Deno 2.7.8, Deno 2.8.0, and Deno 2.9.4 compat data mapping
  • Updated Electron 42 and added 43, 44, and 45 compat data mapping
  • Added Samsung Browser 30 compat data mapping
  • Added Oculus Quest Browser 144+ compat data mapping
  • Added Opera for Android 97, 98, 99, and 100 compat data mapping

4.0.0-alpha.1 - 2026.03.22

Early release for testing some concepts.

NOT FOR USAGE IN REAL PROJECTS.

See more info here: #1310

3.49.0 - 2026.03.16

• Changes v3.48.0...v3.49.0 (373 commits)
• Iterator.range updated following the actual spec version
  • Throw a RangeError on NaN start / end / step
  • Allow null as optionOrStep
• Improved accuracy of Math.{ asinh, atanh } polyfills with big and small values
• Improved accuracy of Number.prototype.toExponential polyfills with big and small values
• Improved performance of atob, btoa, Uint8Array.fromHex, Uint8Array.prototype.setFromHex, and Uint8Array.prototype.toHex, #1503, #1464, #1510, thanks @johnzhou721
• Minor performance optimization polyfills of methods from Map upsert proposal
• Polyfills of methods from Map upsert proposal from the pure version made generic to make it work with polyfilled and native collections
• Wrap Symbol.for in Symbol.prototype.description polyfill for correct handling of empty string descriptions
• Fixed a modern Safari bug in Array.prototype.includes with sparse arrays and fromIndex
• Fixed one more case (Iterator.prototype.take) of a V8 ~ Chromium < 126 bug
• Forced replacement of Iterator.{ concat, zip, zipKeyed } in the pure version for ensuring proper wrapped Iterator instances as the result
• Fixed proxying .return() on exhausted iterator from some methods of iterator helpers polyfill to the underlying iterator
• Fixed double .return() calling in case of throwing error in this method in the internal iterate helper that affected some polyfills
• Fixed closing iterator on IteratorValue errors in the internal iterate helper that affected some polyfills
• Fixed iterator closing in Array.from polyfill on failure to create array property
• Fixed order of arguments validation in Array.fromAsync polyfill
• Fixed a lack of counter validation on MAX_SAFE_INTEGER in Array.fromAsync polyfill
• Fixed order of arguments validation in Array.prototype.flat polyfill
• Fixed handling strings as iterables in Iterator.{ zip, zipKeyed } polyfills
• Fixed some cases of iterators closing in Iterator.{ zip, zipKeyed } polyfills
• Fixed validation of iterators .next() results an objects in Iterator.{ zip, zipKeyed } polyfills
• Fixed a lack of early error in Iterator.concat polyfill on primitive as an iterator
• Fixed buffer mutation exposure in Iterator.prototype.windows polyfill
• Fixed iterator closing in Set.prototype.{ isDisjointFrom, isSupersetOf } polyfill
• Fixed (updated following the final spec) one more case Set.prototype.difference polyfill with updating this
• Fixed DataView.prototype.setFloat16 polyfill in (0, 1) range
• Fixed order of arguments validation in String.prototype.{ padStart, padEnd } polyfills
• Fixed order of arguments validation in String.prototype.{ startsWith, endsWith } polyfills
• Fixed some cases of Infinity handling in String.prototype.substr polyfill
• Fixed String.prototype.repeat polyfill with a counter exceeding 2 ** 32
• Fixed some cases of chars case in escape polyfill
• Fixed named backreferences in RegExp NCG polyfill
• Fixed some cases of RegExp NCG polyfill in combination with other types of groups
• Fixed some cases of RegExp NCG polyfill in combination with dotAll
• Fixed String.prototype.replace with sticky polyfill, #810, #1514
• Fixed RegExp sticky polyfill with alternation
• Fixed handling of some line terminators in case of multiline + sticky mode in RegExp polyfill
• Fixed .input slicing on result object with RegExp sticky mode polyfill
• Fixed handling of empty groups with global and unicode modes in polyfills
• Fixed URLSearchParam.prototype.delete polyfill with duplicate key-value pairs
• Fixed possible removal of unnecessary entries in URLSearchParam.prototype.delete polyfill with second argument
• Fixed an error in some cases of non-special URLs without a path in the URL polyfill
• Fixed some percent encode cases / character sets in the URL polyfill
• Fixed parsing of non-IPv4 hosts ends in a number in the URL polyfill
• Fixed some cases of '' and null host handling in the URL polyfill
• Fixed host parsing with hostname = host:port in the URL polyfill
• Fixed host inheritance in some cases of file scheme in the URL polyfill
• Fixed block of protocol change for file with empty host in the URL polyfill
• Fixed invalid code points handling in UTF-8 decode in the URLSearchParams polyfill
• Fixed some cases of serialization in URL polyfill (/. prefix for non-special URLs with null host and path starting with empty segment)
• Fixed URL polyfill .origin getter with blob scheme
• Fixed a lack of error in URLSearchParams.prototype.set polyfill on calling only with 1 argument
• Fixed handling invalid UTF-8 continuation bytes in URLSearchParams polyfill
• Fixed incomplete sequences with out-of-range continuation bytes handling in URLSearchParams polyfill
• Fixed allowing unexpected symbols in scheme in the URL polyfill
• Fixed repeated ToPropertyKey calling in Reflect.{ get, set, deleteProperty } polyfills
• Fixed Reflect.set polyfill with some descriptors cases
• Fixed Reflect.set polyfill with some non-extensible receiver cases
• Fixed the order of Reflect.construct polyfill arguments validation (observable only in the error message)
• Fixed a lack of error in Reflect.defineProperty polyfill with malformed descriptor
• Fixed a lack of error in JSON.parse polyfill on unterminated object and array literals
• Fixed a lack of error in JSON.parse polyfill on numbers with ., but without a fraction part
• Fixed a lack of error on \u{} in String.dedent polyfill
• Fixed some cases of hex escaping in the end of string in String.dedent polyfill
• Fixed %AsyncFromSyncIteratorPrototype% to make it a little stricter
• Fixed counter in some cases of some AsyncIterator methods
• Fixed order of async iterators closing
• Fixed iterator closing in AsyncIterator.prototype.flatMap polyfill
• Fixed iterator closing in AsyncIterator.prototype.map polyfill on error in underlying iterator .next()
• Fixed iterator closing in AsyncIterator.prototype.take polyfill with return: null
• Fixed validation .return() result as object in AsyncIterator.prototype.take polyfill
• Fixed a lack of error in structuredClone polyfill on attempt to transfer multiple objects, some of which are non-transferable
• Fixed resizable ArrayBuffer transferring where newByteLength exceeds the original maxByteLength
• Fixed possible loss of symbol enumerability in Object.defineProperty in Symbol polyfill
• Fixed return value of Object.defineProperty in Symbol polyfill in Android ~ 2
• Fixed order of %TypedArray%.from arguments validation
• Fixed a lack of error on passing an ArrayBuffer and a negative length to the %TypedArray% and DataView constructors polyfills
• Fixed some cases of @@toStringTag on %TypedArray% polyfill
• Fixed some cases of ToUint8Clamp conversion
• Fixed NaN handling in Date.prototype.setYear polyfill
• Fixed false positive on a WeakMap validation in the pure version
• Fixed some minor { Map, Set }.prototype.forEach moments in the pure version
• Fixed possible error in Array.isTemplateObject polyfill on frozen array
• Fixed semantics of Observable.from with multiple subscriptions of the obsolete ECMAScript Observable proposal polyfill
• Fixed handling of ending zeroes in the fraction part in Number.fromString polyfill
• Fixed esmodules: intersect option of core-js-compat
• Fixed a lack of reactnative alias in core-js-compat types
• Fixed a minor logical bug in the debugging output of core-js-builder
• Fixed ignorance of the obsolete blacklist option of core-js-builder - it should be removed only in the next major release
• In case of bugs in String.prototype.{ match, matchAll, replace, split } in modern engines, add s, d and v flag support to polyfills of those methods
• Just in case, added an extra input string validation to the polyfill of obsolete Number.fromString proposals
• Simplified iOS detection
• Many minor stylistic fixes and optimizations
• Compat data improvements:
  • Math.sumPrecise marked as shipped in V8 ~ Chrome 147
  • Iterator.concat marked as shipped in V8 ~ Chrome 146
  • Iterator.concat marked as shipped in Safari 26.4
  • Because of a bug, Array.prototype.includes marked as not supported in modern Safari
  • Fixed compat data for parseInt and parseFloat
  • Added Deno 2.6.7, 2.7.0 and 2.7.2 compat data mapping
  • Added Electron 42 compat data mapping
  • Added Opera for Android 95 and 96 compat data mapping
  • Added [Oculus Quest Browser 42](https://developers.meta.com/...

3.48.0 - 2026.01.21

• Changes v3.47.0...v3.48.0 (126 commits)
• Map upsert proposal:
  • Built-ins:
    • Map.prototype.getOrInsert
    • Map.prototype.getOrInsertComputed
    • WeakMap.prototype.getOrInsert
    • WeakMap.prototype.getOrInsertComputed
  • Moved to stable ES, January 2026 TC39 meeting
  • Added es. namespace modules, /es/ and /stable/ namespaces entries
• Use CreateDataProperty / CreateDataPropertyOrThrow in some missed cases, #1497
• Minor fix / optimization in the RegExp constructor (NCG and dotAll) polyfill
• Added some more workarounds for a Safari < 13 bug with silent ignore of non-writable array .length
• Added detection of a Webkit bug: Iterator.prototype.flatMap throws on iterator without return method
• Added detection of a V8 ~ Chromium < 144 bug: Uint8Array.prototype.setFromHex throws an error on length-tracking views over ResizableArrayBuffer
• Compat data improvements:
  • Map upsert proposal features marked as shipped in V8 ~ Chrome 145
  • Joint iteration proposal features marked as shipped in FF148
  • Iterator.concat marked as shipped in Bun 1.3.7
  • Added Rhino 1.9.0 compat data
  • Added Deno 2.6 compat data mapping
  • Added Opera Android 93 and 94 compat data mapping
  • Added Electron 41 compat data mapping
  • Iterator.prototype.flatMap marked as supported from Safari 26.2 and Bun 1.2.21 because of a bug: throws on iterator without return method
  • Uint8Array.prototype.setFromHex marked as supported from V8 ~ Chromium 144 because of a bug: throws an error on length-tracking views over ResizableArrayBuffer

3.47.0 - 2025.11.18

• Changes v3.46.0...v3.47.0 (117 commits)
• JSON.parse source text access proposal :
  • Built-ins:
    • JSON.isRawJSON
    • JSON.parse
    • JSON.rawJSON
    • JSON.stringify
  • Moved to stable ES, November 2025 TC39 meeting
  • Added es. namespace modules, /es/ and /stable/ namespaces entries
  • Reworked JSON.stringify internals
• Iterator sequencing proposal:
  • Built-ins:
    • Iterator.concat
  • Moved to stable ES, November 2025 TC39 meeting
  • Added es. namespace modules, /es/ and /stable/ namespaces entries
• Joint iteration proposal:
  • Built-ins:
    • Iterator.zip
    • Iterator.zipKeyed
  • Moved to stage 3, November 2025 TC39 meeting
  • Added /actual/ namespace entries, unconditional forced replacement changed to feature detection
• Fixed increasing .size in URLSearchParams.prototype.append polyfill in IE8-
• Compat data improvements:
  • Iterator.concat marked as shipped in FF147
  • Map upsert proposal features marked as shipped in Safari 26.2
  • Math.sumPrecise marked as shipped in Safari 26.2
  • Uint8Array.{ fromBase64, prototype.setFromBase64 } marked as fixed in Safari 26.2
  • Missed Explicit Resource Management features added in Bun 1.3.0
  • Added Oculus Quest Browser 41 compat data mapping
  • Added Electron 40 compat data mapping

3.46.0 - 2025.10.09

Welcome to our new website, core-js.io, where our documentation is moving!

In addition, you can now follow the project's news in X.

---

• Changes v3.45.1...v3.46.0 (116 commits)
• Map upsert stage 3 proposal:
  • Fixed a FF WeakMap.prototype.getOrInsertComputed bug with callback calling before validation a key
• Iterator chunking proposal:
  • Built-ins:
    • Iterator.prototype.chunks
    • Iterator.prototype.windows
  • Moved to stage 2.7, September 2025 TC39 meeting
  • Iterator.prototype.sliding method replaced with an extra parameter of Iterator.prototype.windows method, tc39/proposal-iterator-chunking/#24, tc39/proposal-iterator-chunking/#26
• Fixed Iterator.zip and Iterator.zipKeyed behavior with mode: 'longest' option, #1469, thanks @lionel-rowe
• Fixed work of Object.groupBy and Iterator.zipKeyed together with Symbol polyfill - some cases of symbol keys on result null-prototype object were able to leak out to for-in
• Compat data improvements:
  • Map upsert proposal features marked as shipped from FF144
  • Added Node 25.0 compat data mapping
  • Added Deno 2.5 compat data mapping
  • Updated Electron 39 compat data mapping
  • Updated Opera 121+ compat data mapping
  • Added Opera Android 92 compat data mapping
  • Added Oculus Quest Browser 40 compat data mapping

3.45.1 - 2025.08.20

• Changes v3.45.0...v3.45.1 (30 commits)
• Fixed a conflict of native methods from Map upsert proposal with polyfilled methods in the pure version
• Added bugs fields to package.json of all packages
• Compat data improvements:
  • Map upsert proposal features marked as shipped from Bun 1.2.20
  • Added Samsung Internet 29 compat data mapping
  • Added Electron 39 compat data mapping

3.45.0 - 2025.08.04

• Changes v3.44.0...v3.45.0 (70 commits)
• Uint8Array to / from base64 and hex proposal:
  • Built-ins:
    • Uint8Array.fromBase64
    • Uint8Array.fromHex
    • Uint8Array.prototype.setFromBase64
    • Uint8Array.prototype.setFromHex
    • Uint8Array.prototype.toBase64
    • Uint8Array.prototype.toHex
  • Moved to stable ES, July 2025 TC39 meeting
  • Added es. namespace modules, /es/ and /stable/ namespaces entries
  • Added detection of a Webkit bug: Uint8Array fromBase64 / setFromBase64 does not throw an error on incorrect length of base64 string
• Math.sumPrecise proposal:
  • Built-ins:
    • Math.sumPrecise
  • Moved to stable ES, July 2025 TC39 meeting
  • Added es. namespace module, /es/ and /stable/ namespaces entries
• Iterator sequencing proposal:
  • Built-ins:
    • Iterator.concat
  • Moved to stage 3, July 2025 TC39 meeting
  • Added /actual/ namespace entries, unconditional forced replacement changed to feature detection
• Map upsert proposal:
  • Built-ins:
    • Map.prototype.getOrInsert
    • Map.prototype.getOrInsertComputed
    • WeakMap.prototype.getOrInsert
    • WeakMap.prototype.getOrInsertComputed
  • Moved to stage 3, July 2025 TC39 meeting
  • Added /actual/ namespace entries, unconditional forced replacement changed to feature detection
• Added missing dependencies to some entries of static Iterator methods
• Fixed Joint Iteration proposal in /stage/ entries
• Compat data improvements:
  • Uint8Array to / from base64 and hex proposal features marked as supported from V8 ~ Chromium 140
  • Uint8Array.{ fromBase64, prototype.setFromBase64 } marked as unsupported in Safari and supported only from Bun 1.2.20 because of a bug: it does not throw an error on incorrect length of base64 string
  • %TypedArray%.prototype.with marked as fixed in Safari 26.0
  • Updated Electron 38 compat data mapping
  • Added Opera Android 91 compat data mapping

3.44.0 - 2025.07.07

• Changes v3.43.0...v3.44.0 (87 commits)
• Uint8Array to / from base64 and hex stage 3 proposal:
  • Fixed several V8 bugs in Uint8Array.fromHex and Uint8Array.prototype.{ setFromBase64, toBase64, toHex }, thanks @brc-dd
• Joint iteration stage 2.7 proposal:
  • Uses Get in Iterator.zipKeyed, following tc39/proposal-joint-iteration#43
• Iterator sequencing stage 2.7 proposal:
  • Iterator.concat no longer reuses IteratorResult object of concatenated iterators, following tc39/proposal-iterator-sequencing#26
• Iterator chunking stage 2 proposal:
  • Added built-ins:
    • Iterator.prototype.sliding
• Number.prototype.clamp stage 2 proposal:
  • clamp no longer throws an error on NaN as min or max, following tc39/proposal-math-clamp#d2387791c265edf66fbe2455eab919016717ce6f
• Fixed some cases of Set.prototype.{ symmetricDifference, union } detection
• Added missing dependencies to some entries of static Iterator methods
• Added missing /full/{ instance, number/virtual }/clamp entries
• Some minor stylistic changes
• Compat data improvements:
  • Added Electron 38 and 39 compat data mapping
  • Added Oculus Quest Browser 38 and 39 compat data mapping
  • Iterator helpers marked as fixed and updated following the latest spec changes in Safari 26.0
  • Set.prototype.{ difference, symmetricDifference, union } marked as fixed in Safari 26.0
  • SuppressedError marked as fixed in FF141
  • Error.isError marked as fixed in Node 24.3
  • setImmediate and clearImmediate marked as available from Deno 2.4
  • Math.sumPrecise marked as shipped in Bun 1.2.18
  • %TypedArray%.prototype.with marked as fixed in Bun 1.2.18