The WebAssembly 3.0 spec is complete! webassembly.org/news/2025-09... This includes major features like GC, 64-bit memories, exceptions, and tail calls.

@dubroy.com alerted me to the Safari release notes (developer.apple.com/documentatio...) say version 26 ships an in-place interpreter for WebAssembly, which is in part based on the Wizard design, but adapted for Safari's use cases. This is cool! Wasm brings all the VMs to tiers!

Nice use of Wasm — bundling lightweight WebAssembly decoders with the data. AnyBlox: A Framework for Self-Decoding Datasets → gienieczko.com/anyblox-paper /ht Jamie Brandon (www.scattered-thoughts.net/log/0054/)

Designing syntax is hard! Some good examples here of what makes language design so tricky.

Many of our friends in North America are back to school already, but we've still got two more weeks of holidays over here. Which means: it's not too late to snag a copy of the book in our summer sale!

Had a fun time recording a podcast episode today…looking forward to sharing it with y'all soon!

Lately I’ve been learning more about WebAssembly fundamentals by reading this fantastic book: wasmgroundup.com . It’s really well written and focuses on how WebAssembly is written by teaching you to write a compiler for it. Which is honestly pretty genius.

The summer holidays just started here in southern Germany. So, it's time for a ☀️ SUMMER SALE ☀️ — Use the code SUMMER25 for a 25% discount on the book until Sept 15: wasmgroundup.com

Wasm modules are enabled by default in the latest version of Node (v24.5.0)! 🎉

Pretty pleased with the ergonomics of the Wasm (macro-)assembler in @ohmjs.org. It's built on the low-level assembler lib we created for @wasmgroundup.com, but has some nice higher-level features, including labeled breaks. I'm particularly proud of the idea to put the block label at the end. 😊

WebAssembly Branch Hinting: From an idea to W3C standard → labs.leaningtech.com/blog/branch... An interesting look at journey from an idea ("it should would be nice if Wasm supported this…") to a standardized feature.

We're still looking for more sponsors! If you or your company can help fund this effort: github.com/sponsors/pd... Since 2017, my work on Ohm has been unpaid. Your sponsorship helps the project be sustainable, ensuring that I can maintain and improve Ohm for many years to come!

acm queue issue out on webassembly, with articles by @littledan.dev, conrad watt, ben titzer, & yours truly: queue.acm.org/issuedetail....

A good question we were asked recently — "Does V8 optimize WebAssembly similar to JS?" The latest post on the V8 blog, "Speculative Optimizations for WebAssembly using Deopts and Inlining", provides some answers! v8.dev/blog/wasm-s...

Here's what I've been working on the past couple months! It's been a lot of fun, and the prototype shows some promising perf improvements (~10x). It's still about 8–10 weeks of effort to productionize this. If you or your company can help fund that work, please get in touch!

Oliver Medhurst talks about Porffor and compiling JavaScript ahead-of-time at the Web Engines Hackfest 2025 @goose.icu www.youtube.com/watch?v=RU5N...

What's the opposite of a cautionary tale? Well, yeah…this is one of those. Learn #wasm and you might just have a helluva lot of fun.

A helpful technique for debugging generated #wasm code!

Wondering if the book is *practical*? I'm currently using the helper library extracted from the book for a new @ohmjs.org feature which will allow you to compile Ohm grammars to Wasm. This will make it possible to use Ohm grammars from Go, Python, etc. Details here 👉 github.com/ohmjs/ohm/is...

Wireworld is a kind of cellular automaton, similar to Conway's Game of Life. Wasm4-Wireworld is an implementation of Wireworld WASM-4 "fantasy console" using Hoot, a Scheme-to-Wasm compiler: spritely.institute/news/hoot-wi...

After using @ohmjs.org to teach WebAssembly, @dubroy.com will be working on first-class #wasm support in Ohm.

Great article by @saelo.bsky.social about the V8 sandbox: v8.dev/blog/sandbox "the overall construction is therefore not unlike the sandboxing model used by WebAssembly"

Would you be interested in a workshop about WebAssembly, based on the content in our book? If so, it'd help us if you could fill out this survey: forms.gle/6Xpv47MKrAs... We're trying to figure out the details — when, where, how long, etc. Fill out the survey and let us know what'd work for you!

Just published a new release of the book with some minor updates: • Added "debugging" section to About the Code • Appendix now has all remaining instructions from the 1.0 spec • (PDF) Fixed some code blocks which didn't show full contents +More! It's all in the changelog.

Something handy for anyone who's trying to debug generated wasm… A PR of ours was merged into the wabt repo yesterday. In the JS version of wasm2wat, you can now opt to skip validation — just like the `--no-check` option in the CLI. Try it out here: webassembly.github.io/wabt/demo/w...

Writing a book can be very educational, who knew?!

As of last December, release 2.0 of the #Wasm specification is “official”! Read Andreas Rossberg's post, which happens to be the first real post on the #WebAssembly website's new News 🗞️ section: webassembly.org/news/2025-03....

Excited to announce the official launch of our online book, WebAssembly from the Ground Up! 🎉 It's the book we wish we'd had 3 years ago. No messing with tools and frameworks. It's a hands-on guide to the core of Wasm: the instruction set and module format. Link below. 👇

With the official launch of the book being next week, we figured it's about time we wrote a Conclusion chapter 😅 Lots more small tweaks & improvements coming this week…

Just published another update to the book: a draft of our last technical chapter, "Odds & Ends". 🎉 It covers a few features that we didn't have room for in the main track of the book: global variables, tables, and the element section.

Happy Friday! We've just published a draft of the FINAL technical chapter of the book. It's called "What Makes WebAssembly Safe?" and we think you're going to enjoy it.

Our book is about building a compiler for a toy, compile-to-Wasm language. At some point, we starting wondering…what's the smallest possible WebAssembly compiler? Could you make one that fits in tweet? 🤔 The answer is yes! wasmgroundup.com/blog/wasm-c...

Nice to see that @moonbitlang.bsky.social is continuing to make progress! MoonBit is a new, Wasm-native programming language with a syntax similar to Rust (although it has a GC): docs.moonbitlang.com/en/latest/

Wasmtime's mechanism for preventing infinitely-executing WebAssembly code is called "fuel" 😄 docs.wasmtime.dev/api/wasmtim...

SpiderMonkey WASI demo — the SpiderMonkey JS engine, compiled to WebAssembly, running in the browser → mozilla-spidermonkey.github.io/sm-wasi-demo/

A great post and a nice peek into what it takes to make a performant Wasm engine.

This looks great, and seems like the perfect compliment to our book! Ours is a step-by-step guide to building a small compiler for a toy language, using the *binary module format*. @d3lm.bsky.social's course will teach you the text format (.wat) with interactive exercises. Why not both? 😄

Love this idea! WebAssembly Wizardry: "Tiny programming challenges designed for learning about WebAssembly by writing it by hand." → github.com/danprince/w...

Hello! We're looking for 1-2 people **who've already bought the book but haven't yet started** and are interesting in working through the first 1-2 chapters LIVE on a video call with me. Interested? Reply here or to the post on the #announcements channel in the book's Discord.

Btw…if you've been holding off on buying, you might not want to wait any longer! We'll be officially launching the book in early 2025 — and accordingly raising the price. Now's your chance to snap a copy before that happens. 😉

Hello Wasmites — We've got a big update for you today, just in time for the holidays! It's a draft of Chapter 10: Arrays and Strings. 🎉 This is definitely one of the most technically challenging chapters of the book…but we think you're going to like it!

Big news! Safari 18.2 is out, with support for WasmGC and tail calls: webkit.org/blog/16301/...

Many programming books start with a small program that prints "Hello, world.” But this book is different. It's only at the end of Chapter 10 that we're ready to tackle that. 😅 Looking forward to releasing the draft very soon!

Did you know that in WebAssembly you can export a function with an empty name?

Reverse Engineering a 218-Byte Wasm Compiler in JavaScript Starting with a 218-byte one-liner that implements a Reverse Polish Notation arithmetic compiler, we'll work backward to transform it into readable JavaScript by removing one code golf trick at a time.

Some *very* interesting Wasm-related features in the latest version of Deno (v2.1): https://docs.deno.com/runtime/reference/wasm/ • Import .wasm modules directly • Calls into WebAssembly are type checked (!) • Wasm modules can import .ts modules directly (!!)

Hello, World! (from the ground up)