• Changesv3.46.0...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
  • Addedes. namespace modules,/es/ and/stable/ namespaces entries
  • ReworkedJSON.stringify internals
• Iterator sequencing proposal:
  • Built-ins:
    • Iterator.concat
  • Moved to stable ES,November 2025 TC39 meeting
  • Addedes. 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 inURLSearchParams.prototype.append polyfill in IE8-
• Compat data improvements:
  • Iterator.concat marked asshipped 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
  • MissedExplicit Resource Management featuresadded in Bun 1.3.0
  • Added Oculus Quest Browser 41 compat data mapping
  • Added Electron 40 compat data mapping

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

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

• Changesv3.45.1...v3.46.0 (116 commits)
• Map upsert stage 3 proposal:
  • Fixeda FFWeakMap.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 ofIterator.prototype.windows method,tc39/proposal-iterator-chunking/#24,tc39/proposal-iterator-chunking/#26
• FixedIterator.zip andIterator.zipKeyed behavior withmode: 'longest' option,#1469, thanks@lionel-rowe
• Fixed work ofObject.groupBy andIterator.zipKeyed together withSymbol polyfill - some cases of symbol keys on resultnull-prototype object were able to leak out tofor-in
• Compat data improvements:
  • Map upsert proposal features marked as shipped from FF144
  • AddedNode 25.0 compat data mapping
  • AddedDeno 2.5 compat data mapping
  • Updated Electron 39 compat data mapping
  • Updated Opera 121+ compat data mapping
  • AddedOpera Android 92 compat data mapping
  • Added Oculus Quest Browser 40 compat data mapping

• Changesv3.45.0...v3.45.1 (30 commits)
• Fixed a conflict of native methods fromMap upsert proposal with polyfilled methods in the pure version
• Addedbugs fields topackage.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

• Changesv3.44.0...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
  • Addedes. 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
  • Addedes. 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 staticIterator methods
• FixedJoint Iteration proposal in/stage/ entries
• Compat data improvements:
  • Uint8Array to / from base64 and hex proposal features marked assupported 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

• Changesv3.43.0...v3.44.0 (87 commits)
• Uint8Array to / from base64 and hex stage 3 proposal:
  • Fixedseveral V8 bugs inUint8Array.fromHex andUint8Array.prototype.{ setFromBase64, toBase64, toHex }, thanks@brc-dd
• Joint iteration stage 2.7 proposal:
  • UsesGet inIterator.zipKeyed, followingtc39/proposal-joint-iteration#43
• Iterator sequencing stage 2.7 proposal:
  • Iterator.concat no longer reusesIteratorResult object of concatenated iterators, followingtc39/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 onNaN asmin ormax, followingtc39/proposal-math-clamp#d2387791c265edf66fbe2455eab919016717ce6f
• Fixed some cases ofSet.prototype.{ symmetricDifference, union } detection
• Added missing dependencies to some entries of staticIterator 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 markedas fixed in FF141
  • Error.isError markedas fixed in Node 24.3
  • setImmediate andclearImmediate marked as availablefrom Deno 2.4
  • Math.sumPrecise marked asshipped in Bun 1.2.18
  • %TypedArray%.prototype.with marked as fixed in Bun 1.2.18

• Changesv3.42.0...v3.43.0 (139 commits)
• Explicit Resource Management proposals:
  • Built-ins:
    • Symbol.dispose
    • Symbol.asyncDispose
    • SuppressedError
    • DisposableStack
      • DisposableStack.prototype.dispose
      • DisposableStack.prototype.use
      • DisposableStack.prototype.adopt
      • DisposableStack.prototype.defer
      • DisposableStack.prototype.move
      • DisposableStack.prototype[@@dispose]
    • AsyncDisposableStack
      • AsyncDisposableStack.prototype.disposeAsync
      • AsyncDisposableStack.prototype.use
      • AsyncDisposableStack.prototype.adopt
      • AsyncDisposableStack.prototype.defer
      • AsyncDisposableStack.prototype.move
      • AsyncDisposableStack.prototype[@@asyncDispose]
    • Iterator.prototype[@@dispose]
    • AsyncIterator.prototype[@@asyncDispose]
  • Moved to stable ES,May 2025 TC39 meeting
  • Addedes. namespace module,/es/ and/stable/ namespaces entries
• Array.fromAsync proposal:
  • Built-ins:
    • Array.fromAsync
  • Moved to stable ES,May 2025 TC39 meeting
  • Addedes. namespace module,/es/ and/stable/ namespaces entries
• Error.isError proposal:
  • Built-ins:
    • Error.isError
  • Moved to stable ES,May 2025 TC39 meeting
  • Addedes. namespace module,/es/ and/stable/ namespaces entries
• AddedJoint iteration stage 2.7 proposal:
  • Added built-ins:
    • Iterator.zip
    • Iterator.zipKeyed
• AddedIterator chunking stage 2 proposal:
  • Added built-ins:
    • Iterator.prototype.chunks
    • Iterator.prototype.windows
• Number.prototype.clamp proposal:
  • Built-ins:
    • Number.prototype.clamp
  • Moved to stage 2,May 2025 TC39 meeting
  • Math.clamp was replaced withNumber.prototype.clamp
  • Removed aRangeError ifmin <= max or+0 min and-0 max,tc39/proposal-math-clamp/#22
• Always check regular expression flags byflags getterPR. Native methods are not fixed, only own implementation updated for:
  • RegExp.prototype[@@match]
  • RegExp.prototype[@@replace]
• Improved handling ofRegExp flags in polyfills of some methods in engines without proper support ofRegExp.prototype.flags and without polyfill of this getter
• Added feature detection fora WebKit bug that occurs whenthis is updated whileSet.prototype.difference is being executed
• Added feature detection fora WebKit bug that occurs when iterator record of a set-like object isn't called before cloningthis in the following methods:
  • Set.prototype.symmetricDifference
  • Set.prototype.union
• Added feature detection fora bug in V8 ~ Chromium < 126. Following methods should throw an error on invalid iterator:
  • Iterator.prototype.drop
  • Iterator.prototype.filter
  • Iterator.prototype.flatMap
  • Iterator.prototype.map
• Added feature detection fora WebKit bug: incorrect exception thrown byIterator.from when underlying iterator'sreturn method isnull
• Added feature detection for a FF bug: incorrect exception thrown byArray.prototype.with when index coercion fails
• Added feature detection for a WebKit bug:TypedArray.prototype.with should truncate negative fractional index to zero, but instead throws an error
• Worked around a bug of many different tools (example) with incorrect transforming and breaking JS syntax on getting a method from a number literal
• Fixed deoptimization of thePromise polyfill in the pure version
• Added some missed dependencies to/iterator/flat-map entries
• Some other minor fixes and improvements
• Compat data improvements:
  • AddedDeno 2.3 andDeno 2.3.2 compat data mapping
  • Updated Electron 37 compat data mapping
  • Added Opera Android 90 compat data mapping
  • Error.isError marked not supported in Node because ofa bug
  • Set.prototype.difference marked as not supported in Safari and supported only from Bun 1.2.5 because ofa bug
  • Set.prototype.{ symmetricDifference, union } marked as not supported in Safari and supported only from Bun 1.2.5 because ofa bug
  • Iterator.from marked as not supported in Safari and supported only from Bun 1.2.5 because ofa bug
  • Iterators closing on early errors inIterator helpers marked as implemented from FF141
  • Array.prototype.with marked as supported only from FF140 because it throws an incorrect exception when index coercion fails
  • TypedArray.prototype.with marked as unsupported in Bun and Safari because it should truncate negative fractional index to zero, but instead throws an error
  • DisposableStack andAsyncDisposableStack marked asshipped in FF141 (SuppressedError hasa bug)
  • AsyncDisposableStack bugs marked as fixed in Deno 2.3.2
  • SuppressedError bugs (extra arguments support andarity) marked as fixed in Bun 1.2.15

• Changesv3.41.0...v3.42.0 (142 commits)
• Map upsert proposal:
  • Moved to stage 2.7,April 2025 TC39 meeting
  • Validation order ofWeakMap.prototype.getOrInsertComputed updated followingtc39/proposal-upsert#79
  • Built-ins:
    • Map.prototype.getOrInsert
    • Map.prototype.getOrInsertComputed
    • WeakMap.prototype.getOrInsert
    • WeakMap.prototype.getOrInsertComputed
• Don't call well-knownSymbol methods forRegExp on primitive values followingtc39/ecma262#3009:
  • For avoid performance regression, temporarily, only in owncore-js implementations
  • Built-ins:
    • String.prototype.matchAll
    • String.prototype.match
    • String.prototype.replaceAll
    • String.prototype.replace
    • String.prototype.search
    • String.prototype.split
• Added workaround for theUint8Array.prototype.setFromBase64bug in some of Linux builds of WebKit
• Implemented early-error iterator closing followingtc39/ecma262#3467, including fix ofa WebKit bug, in the following methods:
  • Iterator.prototype.drop
  • Iterator.prototype.every
  • Iterator.prototype.filter
  • Iterator.prototype.find
  • Iterator.prototype.flatMap
  • Iterator.prototype.forEach
  • Iterator.prototype.map
  • Iterator.prototype.reduce
  • Iterator.prototype.some
  • Iterator.prototype.take
• Fixed missing forced replacement ofAsyncIterator helpers
• Added closing of sync iterator when async wrapper yields a rejection followingtc39/ecma262#2600. Affected methods:
  • Array.fromAsync (due to the lack of async feature detection capability - temporarily, only in owncore-js implementation)
  • AsyncIterator.from
  • Iterator.prototype.toAsync
• Added detection for throwing onundefined initial parameter inIterator.prototype.reduce (seeWebKit bug)
• core-js-compat andcore-js-builder API:
  • Added'intersect' support fortargets.esmodules (Babel 7 behavior)
  • Fixed handling oftargets.esmodules: true (Babel 7 behavior)
• Compat data improvements:
  • Explicit Resource Management features disabled (again) in V8 ~ Chromium 135 and re-added in 136
  • RegExp.escape marked asshipped from V8 ~ Chromium 136
  • Error.isError marked asshipped from FF138
  • Explicit Resource Management features re-enabled inDeno 2.2.10
  • Iterator helpers proposal features marked as supported from Deno 1.38.1 since it seems they were disabled in 1.38.0
  • Iterator.prototype.{ drop, reduce, take } methods marked as fixed in Bun 1.2.11
  • AddedNodeJS 24.0 compat data mapping
  • Updated Electron 36 and added Electron 37 compat data mapping
  • Added Opera Android88 and89 compat data mapping
  • Added Oculus Quest Browser 37 compat data mapping

• Changesv3.40.0...v3.41.0 (85 commits)
• RegExp.escape proposal:
  • Built-ins:
    • RegExp.escape
  • Moved to stable ES,February 2025 TC39 meeting
  • Addedes. namespace module,/es/ and/stable/ namespaces entries
• Float16 proposal:
  • Built-ins:
    • Math.f16round
    • DataView.prototype.getFloat16
    • DataView.prototype.setFloat16
  • Moved to stable ES,February 2025 TC39 meeting
  • Addedes. namespace modules,/es/ and/stable/ namespaces entries
• Math.clamp stage 1 proposal:
  • Built-ins:
    • Math.clamp
  • Extracted fromoldMath extensions proposal,February 2025 TC39 meeting
  • Added arguments validation
  • Added new entries
• Added a workaround of a V8AsyncDisposableStack bug,tc39/proposal-explicit-resource-management/256
• Compat data improvements:
  • DisposableStack,SuppressedError andIterator.prototype[@@dispose] marked asshipped from V8 ~ Chromium 134
  • Error.isError added and marked asshipped from V8 ~ Chromium 134
  • Math.f16round andDataView.prototype.{ getFloat16, setFloat16 } marked asshipped from V8 ~ Chromium 135
  • Iterator helpers proposal features marked asshipped from Safari 18.4
  • JSON.parse source text access proposal features marked asshipped from Safari 18.4
  • Math.sumPrecise marked as shipped from FF137
  • AddedDeno 2.2 compat data and compat data mapping
    • Explicit Resource Management features are available in V8 ~ Chromium 134, but not in Deno 2.2 based on it
  • Updated Electron 35 and added Electron 36 compat data mapping
  • UpdatedOpera Android 87 compat data mapping
  • Added Samsung Internet 28 compat data mapping
  • Added Oculus Quest Browser 36 compat data mapping

• Changesv3.39.0...v3.40.0 (130 commits)
• AddedError.isError stage 3 proposal:
  • Added built-ins:
    • Error.isError
  • We have no bulletproof way to polyfill this method / check if the object is an error, so it's an enough naive implementation that is marked as.sham
• Explicit Resource Management stage 3 proposal:
  • Updated the way async disposing of only sync disposable resources,tc39/proposal-explicit-resource-management/218
• Iterator sequencing stage 2.7 proposal:
  • ReuseIteratorResult objects when possible,tc39/proposal-iterator-sequencing/17,tc39/proposal-iterator-sequencing/18, December 2024 TC39 meeting
• Added a fix ofV8 < 12.8 /NodeJS < 22.10 bug with handling infinite length of set-like objects inSet methods
• OptimizedDataView.prototype.{ getFloat16, setFloat16 } performance,#1379, thanks@LeviPesin
• Dropped unneeded feature detection of non-standard%TypedArray%.prototype.toSpliced
• Dropped possible re-usage of some non-standard / early stage features (likeMath.scale) available on global
• Some other minor improvements
• Compat data improvements:
  • RegExp.escape marked as shipped from Safari 18.2
  • Promise.try marked as shipped from Safari 18.2
  • Math.f16round andDataView.prototype.{ getFloat16, setFloat16 } marked as shipped from Safari 18.2
  • Uint8Array to / from base64 and hex proposal methods marked as shipped from Safari 18.2
  • JSON.parse source text access proposal features marked asshipped from FF135
  • RegExp.escape marked as shippedfrom FF134
  • Promise.try marked as shipped from FF134
  • Symbol.dispose,Symbol.asyncDispose andIterator.prototype[@@dispose] marked as shipped from FF135
  • JSON.parse source text access proposal features marked as shipped from Bun 1.1.43
  • Fixed NodeJS version whereURL.parse was added - 22.1 instead of 22.0
  • AddedDeno 2.1 compat data mapping
  • AddedRhino 1.8.0 compat data with significant number of modern features
  • Added Electron 35 compat data mapping
  • Updated Opera 115+ compat data mapping
  • Added Opera Android86 and 87 compat data mapping

• Changesv3.38.1...v3.39.0
• Iterator helpers proposal:
  • Built-ins:
    • Iterator
      • Iterator.from
      • Iterator.prototype.drop
      • Iterator.prototype.every
      • Iterator.prototype.filter
      • Iterator.prototype.find
      • Iterator.prototype.flatMap
      • Iterator.prototype.forEach
      • Iterator.prototype.map
      • Iterator.prototype.reduce
      • Iterator.prototype.some
      • Iterator.prototype.take
      • Iterator.prototype.toArray
      • Iterator.prototype[@@toStringTag]
  • Moved to stable ES,October 2024 TC39 meeting
  • Addedes. namespace modules,/es/ and/stable/ namespaces entries
• Promise.try:
  • Built-ins:
    • Promise.try
  • Moved to stable ES,October 2024 TC39 meeting
  • Addedes. namespace module,/es/ and/stable/ namespaces entries
  • Fixed/actual|full/promise/try entries for the callback arguments support
• Math.sumPrecise proposal:
  • Built-ins:
    • Math.sumPrecise
  • Moved to stage 3,October 2024 TC39 meeting
  • Added/actual/ namespace entries, unconditional forced replacement changed to feature detection
• AddedIterator sequencing stage 2.7 proposal:
  • Added built-ins:
    • Iterator.concat
• Map upsert stage 2 proposal:
  • Updated to the new API following the October 2024 TC39 meeting
  • Added built-ins:
    • Map.prototype.getOrInsert
    • Map.prototype.getOrInsertComputed
    • WeakMap.prototype.getOrInsert
    • WeakMap.prototype.getOrInsertComputed
• Extractors proposal moved to stage 2,October 2024 TC39 meeting
• Usage of@@species pattern removed from%TypedArray% andArrayBuffer methods,tc39/ecma262/3450:
  • Built-ins:
    • %TypedArray%.prototype.filter
    • %TypedArray%.prototype.filterReject
    • %TypedArray%.prototype.map
    • %TypedArray%.prototype.slice
    • %TypedArray%.prototype.subarray
    • ArrayBuffer.prototype.slice
• Some other minor improvements
• Compat data improvements:
  • Uint8Array to / from base64 and hex proposal methods marked asshipped from FF133
  • AddedNodeJS 23.0 compat data mapping
  • self descriptoris fixed in Deno 1.46.0
  • Added Deno1.46 and2.0 compat data mapping
  • Iterator helpers proposal methods marked asshipped from Bun 1.1.31
  • Added Electron 34 and updated Electron 33 compat data mapping
  • AddedOpera Android 85 compat data mapping
  • Added Oculus Quest Browser 35 compat data mapping