Deno v1.27.0 — Release Notes & Engineering Impact

Source available — automated, not human-reviewed

Component: deno · Channel: stable. Automated analysis, not a compatibility certification. How this works.

Analysis updated: 2026-11-01.

Compatibility not verified — check source notes

📄 .MD

✨ Features 6 ⚡ Improvements 6 🔧 Bug Fixes 6

⚡ Executive Summary (TL;DR)

Deno v1.27.0. Source highlight: feat(core): enable --harmony-change-array-by-copy V8 flag (#16429)

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Who Does This Impact? (Role-Based Analysis)

💻 Software Engineers & Devs

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📊 Product & Engineering Leads

Use the documented changes to assess relevance to your product; release frequency alone is not a quality measure.

⚙️ DevOps & Security

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✨ New Features & Capabilities (6)

feat(core): enable --harmony-change-array-by-copy V8 flag (#16429)
feat(cli): check for updates in background (#15974)
feat(cli): show error cause recursion information (#16384)
feat(ext/ffi): Make op_ffi_ptr_of fast (#16297)
feat(ext/net): add reuseAddress option for UDP (#13849)
feat(ext/net): reusePort for TCP on Linux (#16398)

⚡ Performance & Enhancements (6)

perf(core): avoid creating global handles in `op_queue_microtask` (#16359)
perf(core): avoid isolate slots for ModuleMap (#16409)
perf(core): do not drive JsInspector by default (#16410)
perf(core): don't access isolate slots for JsRuntimeState (#16376)
perf(ext/ffi): Fast UnsafePointerView read functions (#16351)
perf(ext/flash): optimize path response streams (#16284)

🔧 Bug Fixes & Patches (6)

fix(build) assume a custom compiler will support --export-dynamic-symbol-list
fix(cli): Fixed bug where the progress bar did not clear (#16401)
fix(cli): do not log update checker when log level is quiet (#16433)
fix(compile): show an error when using npm specifiers (#16430)
fix(core) Include causes when converting anyhow errors to JS exceptions
fix(ext/fetch): fix `size_hint` on response body resource (#16254)

📄 View Raw Release Notes (Original Developer Log)

### 1.27.0 / 2022.10.27 - feat(core): enable --harmony-change-array-by-copy V8 flag (#16429) - feat(cli): check for updates in background (#15974) - feat(cli): show error cause recursion information (#16384) - feat(ext/ffi): Make op_ffi_ptr_of fast (#16297) - feat(ext/net): add reuseAddress option for UDP (#13849) - feat(ext/net): reusePort for TCP on Linux (#16398) - feat(ext/web): use ArrayBuffer.was_detached() (#16307) - feat(lint): add a report lint config setting (#16045) - feat(runtime): make kill signal optional (#16299) - feat(task): remove warning about being unstable (#16281) - feat(task): support `sleep` suffixes (#16425) - feat(unstable/npm): initial type checking of npm specifiers (#16332) - feat(unstable/task): fail task on async command failure (#16301) - feat(update): prompt for new version once per day (#16375) - feat(upgrade): check if user has write access to deno exe (#16378) - feat: Add new lockfile format (#16349) - feat: Stabilize Deno.consoleSize() API (#15933) - feat: Stabilize Deno.osRelease() API (#15973) - feat: Stabilize Deno.stdin.setRaw() (#16399) - feat: introduce navigator.language (#12322) - feat: stabilize Deno.futime() and Deno.futimeSync() (#16415) - feat: stabilize Deno.loadavg() (#16412) - feat: stabilize Deno.utime() and Deno.utimeSync() (#16421) - feat: support inlay hints (#16287) - fix(build) assume a custom compiler will support --export-dynamic-symbol-list linker flag. (#16387) - fix(cli): Fixed bug where the progress bar did not clear (#16401) - fix(cli): do not log update checker when log level is quiet (#16433) - fix(compile): show an error when using npm specifiers (#16430) - fix(core) Include causes when converting anyhow errors to JS exceptions (#16397) - fix(ext/fetch): fix `size_hint` on response body resource (#16254) - fix(ext/ffi): Use BufferSource for FFI buffer types (#16355) - fix(ext/ffi): Use PointerValue in UnsafePointerView and UnsafeFnPointer types (#16354) - fix(ext/net): don't remove sockets on unix listen (#16394) - fix(ext/net): return an error from `startTls` and `serveHttp` if the original connection is captured elsewhere (#16242) - fix(lsp): allow caching deps in non-saved files (#16353) - fix(lsp): regression - error when removing file (#16388) - fix(npm): add support for npm packages in lock files (#15938) - fix(typescript): allow synthetic default imports when using `ModuleKind.ESNext` (#16438) - fix(upgrade): Added error message when using canary option with M1 (#16382) - fix(upgrade): put prompt date in the past when creating a file (#16380) - fix: listenTlsWithReuseAddr test (#16420) - fix: move generated napi symbols to cli/ (#16330) - fix: upgrade swc_ecma_parser to 0.122.19 - deno_ast 0.20 (#16406) - perf(core): avoid creating global handles in `op_queue_microtask` (#16359) - perf(core): avoid isolate slots for ModuleMap (#16409) - perf(core): do not drive JsInspector by default (#16410) - perf(core): don't access isolate slots for JsRuntimeState (#16376) - perf(ext/ffi): Fast UnsafePointerView read functions (#16351) - perf(ext/flash): optimize path response streams (#16284) - perf(ext/streams): fast path when consuming body of tee'd stream (#16329) - perf(ext/web): add op_encode_binary_string (#16352) - perf(ext/web): optimize transferArrayBuffer (#16294) - perf(ext/web/encoding): avoid copy in decode (#16364) - perf(ext/websocket): optimize `op_ws_next_event` (#16325) - perf(ext/websocket): optimize socket.send (#16320) - perf(serde_v8): `serde_v8::StringOrBuffer` return JS ArrayBuffer instead of Uint8Array (#16360)

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