What's New in Node.js 27

Node.js 27 begins a new annual release schedule: major versions now correspond to the calendar year, the odd/even distinction is gone, and every release is intended to become LTS. Version 27 started an Alpha phase in October 2026, with its Current release planned for April 2027 and LTS promotion for October. Its first Alpha upgrades to V8 15.6, adding synchronous iterator helpers for pairing sequences with Iterator.zip() or Iterator.zipKeyed(), joining values, and searching without first building arrays. Iterator.zip() can stop at the shortest input, require equal lengths, or pad missing values. Math.sumPrecise() improves the accuracy of sums by avoiding the rounding errors that accumulate in ordinary floating-point addition.

Node.js 27 also introduces node:net/promises and async-iterable TCP servers, and makes the Virtual File System available without a flag. Other core changes include atomic temporary files with fs.mkstemp(), native fs.glob(), an allow-env permission, stable test-runner watch mode and mock helpers, and a 65-second HTTP keep-alive timeout. The default heap limit rises to 4 GB on an 8 GB machine, while V8 and OpenSSL updates may affect sorting, cryptography, serialization, and runtime behavior. Upgraders should check memory use, especially in multi-process deployments, and account for a breaking HTTP change: req.headers now has a null prototype, which can affect code that relies on ordinary object methods or inheritance. The iterator helpers are synchronous and do not work directly with async iterators or streams.