Node.js v27.0.0-alpha.0.0.0 released!

[NewsBot]

Node.js v27.0.0-alpha.0.0.0 has been released.

Notable Changes

V8 15.6

The V8 engine is updated to version 15.6.75.13, up from 14.6 in Node.js 26. Highlights:

• New language features enabled by default: Math.sumPrecise(), Intl.Locale.prototype.variants, Iterator.prototype.join(), Iterator.prototype.includes(), Iterator.zip() and Iterator.zipKeyed().
• Experimental features behind flags: import defer (--js-defer-import-eval), Immutable ArrayBuffer (--js-immutable-arraybuffer) and RegExp buffer boundaries (--js-regexp-buffer-boundaries).
• Memory: when --max-old-space-size is not set, the default heap size limit is now half of the physical memory clamped between 256 MB and 4 GB, and memory held by Buffer and ArrayBuffer instances now counts toward the heap limit. Applications that relied on the previous defaults should set --max-old-space-size explicitly.
• Serialization: v8.serialize(), structuredClone() and postMessage() use a new format that older Node.js releases cannot read. v8.cachedDataVersionTag() and the compile cache also change on every Node.js patch of V8, not only on V8 version changes.
• Observable behavior changes: Math methods now use LLVM’s libm and may differ in the last bit; Math.random() sequences change for a given --random-seed; error.stack is no longer looked up through the prototype chain; await incurs fewer microtasks; Array.prototype.sort() uses PowerSort for large arrays and remains stable.
• Heap snapshots include internal objects, numeric values and full script sources. Taking one takes about twice as long and the file is about twice as large.
• WebAssembly: asm.js is no longer compiled to WebAssembly, and the --experimental-wasm-<name> flags are renamed --wasm-<name>.

A full changelog of the V8 changes between 14.6 and 15.6 will be shared soon.

Contributed by Joyee Cheung in #65161, #66537 and [#66601](no · GitHub…

Link: Release 2026-10-29, Version 27.0.0-alpha.0.0.0 (Alpha), @RafaelGSS · nodejs/node · GitHub