Deno Land has published Deno 2.9, an update of the company’s JavaScript/TypeScript/WebAssembly runtime that features deno desktop, a mechanism for building native desktop applications from the web stack developers already know.
Introduced June 25, Deno 2.9 also improves startup time, memory use, and HTTP throughput, the company said. Deno installation instructions can be found at docs.deno.com.
With Deno 2.9, users can point deno desktop at a script or a web framework project to produce a native and self-contained desktop application where the UI runs in a webview and the logic runs in Deno. Because deno desktop is built on the same machinery as deno compile, the output is a single, distributable binary with code and assets embedded, Deno Land said.
Also in Deno 2.9, a hello-world program now cold-starts in about half the time it took in 2.8 (34ms down to 17ms), the company said. This improvement results from a combination of factors including lazy-loadingnode: globals out of the snapshot, gating the eager Node bootstrap to Node workers, a V8 code cache for residual lazy-loaded ESM modules, and a minified snapshot.
Deno 2.9 also brings improvements in memory usage, specifically memory under load. In Deno 2.8, resident set size grew with the workload, from roughly 94 MB serving plaintext to 197 MB streaming 1 MiB bodies, whereas in Deno 2.9 it stays essentially flat, holding around 62 MB no matter what the server is doing. This works out to 2.2x less peak resident set size on the real world workload scenario and 3.1x less on 1 MiB bodies, according to Deno Land. The upshot is that the same machine can run far more concurrent Deno.serveinstances before it runs out of headroom, the company said.
Further, HTTP throughput improvements in Deno 2.9 make Deno.serve faster across the board. Real-world workload scenario gains 1.27x, plaintext scenario gains 1.11x, and 1 MiB bodies scenario gains 1.18x, helped by a new Deno-owned HTTP/1.1 serving path, the company said.
Finally, Deno 2.9 advances its Node.js compatibility target to Node.js 26. The reported version moves up accordingly and the node-compat test suite Deno runs against is bumped to 26.3.0.
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