How X (Twitter) is Rebuilding Its Web App — X is replacing three servers with one app built on React, Vite and Fastify. Yagiz, famed for his performance work on Node, explains the streaming architecture behind it, along with some bottlenecks they had to fix, like how hundreds of tiny JavaScript files slowed startup.

Yagiz Nizipli (X Engineering Blog)

Why Standard Webhooks Hit 118m npm Downloads a Month — OpenAI, Anthropic, and Gemini all sign webhooks with Standard Webhooks, the open spec Svix started. That's one finding in the State of Webhooks 2027, where we scored 489 API companies on retries and signatures. Immediate download, no email required.

Svix sponsor

Parcel 3 Alpha: The Bundler Rewritten in Rust — A ground-up Rust rewrite of the popular bundler that the team reports is up to 100x faster than Parcel 2 at cold builds of React Spectrum. It runs as a standalone binary without Node, with support for native plugins written in Rust, Go or Swift, while JavaScript plugins run on an embedded QuickJS runtime.

The Parcel Team

Experiments with Multithreaded JavaScript — What would JavaScript look like if threads could share objects directly? Former TC39 delegate Erik Arvidsson explores three approaches: in a Porffor fork, as a TypeScript library with an ownership checker, and as an implementation of the TC39 structs proposal. Each has a playground to try.

Erik Arvidsson

The New JavaScript Features Between V8 14.6 and 15.6 — Node 27, released in alpha recently, is built on V8 15.6, and Joyee tours what that brings to developers, including Math.sumPrecise, new iterator methods, and some behavior changes in sorting, dates and promises, all with sample code.

Joyee Cheung

How to Build Your Own Automated Debugging Workflow — Connect your coding agent to Sentry and turn errors into fix PRs. See the guides and recipes in the resource hub.

Sentry sponsor

Spreading Liquid with three.js — A technical explanation of a 'liquid-spreading' effect originally built for a cosmetics site. The in-page demo is fun to play with and this could be handy if you want to create paint-like effects.

Misaki Nakano

Reviving Facebook's Abandoned JavaScript Optimizer — Prettier creator James Long put agents to work resurrecting Prepack, Facebook's attempt to make JavaScript faster by running it ahead of time. There's an experimental demo that shows off the gains on a sample React app.

James Long

Yavashark: Building a JavaScript Engine for 950 Days Straight — A solo developer's progress report on a Rust-based engine they're building that passes around 82% of test262 and can server-render a React app. There's a playground to try it for yourself.

Sharktheone

EmbedPDF 3.0: A PDF Viewer for Any JavaScript App — An open-source PDF viewer for vanilla JavaScript, React, Vue, Svelte and Angular. The v3 rebuild offers a ready-made viewer, headless components for custom UIs, and a standalone PDF engine. Try the demo.

EmbedPDF

Embed an Office Editor Your App's AI Agent Can Use — DOCX/XLSX/PPTX editing in your app with your model and workflow. Agents make targeted edits, and users refine the file.

Thinkfree sponsor

chrome-capture: Record a Chrome Tab at 60-120fps to an MP4 File — It's been three years since we've linked to Paul Irish (once a frequent fixture in JavaScript Weekly!) but he's back with a neat, compact tool you can run with npx to record a Chrome tab at high quality including audio to an MP4 video.

Paul Irish

Text.js: React Apps That Render in the Browser Console — Really! A React 19 framework whose 'screen' is the DevTools console, with routing, keyboard input, layout primitives and ASCII fonts. Open the console on the homepage to try it, then bunx create-text-app if you're tempted. GitHub repo.

Anomaly

Jeasx 3.0: Server-Rendered JSX, Now Streaming — A minimal framework that uses JSX purely as a server-side templating language (with no React and no hydration) on top of Fastify and esbuild. v3 streams pages while async components are still loading and renders ~2x faster. Live examples.

Jeasx