A new world for security-critical projects

Jco (@bytecodealliance/jco on NPM)is a “multi-tool for the JS WebAssembly ecosystem.” At the 2026 Bytecode Alliance Plumbers Summit, Technical Steering Committee member Bailey Hayes put it another way: Jco is “like five projects in one.” It’s certainly a project with many facets—five big ones, arguably! Recognizing what those facets are, and how they fit together, is the key to understanding why Jco matters beyond the JavaScript ecosystem. In this blog series, we’ll draw on Victor Adossi’s Plumbers Summit presentation to take an in-depth look at Jco from five different perspectives, in order to better grasp how you can use (and contribute to!) Jco today. There’s a lot to unpack here, so in this first post, we’ll try to get to grips with Jco as a layered architecture that brings together many pieces of the Wasm and JS ecosystem.

The Bytecode Alliance is pleased to invite you to the next installment in our ongoing Plumbers Summits event series, each designed to bring our members and community together to collectively contribute to the strategic planning for the upcoming year. Our next event will be held Wednesday and Thursday, February 25 and 26, 2026. This will be an all online event, supporting full remote participation for anyone anywhere, with sessions recorded so they can be watched anytime afterward via our YouTube channel

In April of 2015, Luke Wagner made the first commits to a new repository called WebAssembly/design, adding a high-level design document for a “binary format to serve as a web compilation target.”

Function inlining is one of the most important compiler optimizations, not because of its direct effects, but because of the follow-up optimizations it unlocks. It may reveal, for example, that an otherwise-unknown function parameter value is bound to a constant argument, which makes a conditional branch unconditional, which in turn exposes that the function will always return the same value. Inlining is the catalyst of modern compiler optimization.

This is a blog post outlining the odyssey I recently took to implement the Wasm exception-handling proposal in Wasmtime, the open-source WebAssembly engine for which I’m a core team member/maintainer, and its Cranelift compiler backend.

Wasmtime is a fast, secure, standards compliant and lightweight WebAssembly (Wasm) runtime. As of Wasmtime 35, Winch supports AArch64 for Core Wasm proposals, along with additional Wasm proposals like the Component Model and Custom Page Sizes.

Wasmtime’s 33.0.0 release supports invoking Wasm component exports directly from the command line with the new --invoke flag. This article walks through building a Wasm component in Rust and using wasmtime run --invoke to execute specific functions (enabling powerful workflows for scripting, testing, and integrating Wasm into modern development pipelines).

The Bytecode Alliance is very happy to announce a significant milestone for both Wasmtime and the Bytecode Alliance: Wasmtime has officially been promoted to become the BA’s first Core Project. As someone deeply involved in Wasmtime and the proposal process, I’m incredibly excited to share this news and what it signifies.

Wasmtime is a lightweight WebAssembly runtime built for speed, security, and standards-compliance. Wasmtime now supports long-term-support (LTS) releases that are maintained with security fixes for 2 years after their initial release.