How Firefox renders web components
How Firefox turns a custom element into pixels, traced through Gecko's own source, from the registry to the reactions stack to the flattened tree Stylo styles.
Front-end & design systems studio
Let's build something great together.
We build the design systems & front-end foundations behind consistent, accessible products — so your teams ship faster with less rework & less risk.
Built with teams at Google, Adobe & Red Hat
About us
We turn front-end friction into systems your teams ship on with confidence.
If your product experience is inconsistent, your handoff is brittle, or your front-end foundation is slowing delivery, we help you turn that friction into a scalable system: clear standards, accessible components, and a codebase your team can build on.
Founded by Cassondra, a front-end architect with deep experience in web components and design systems, Allons-y helps organizations — big or small — scale their work without trading speed for accessibility.
Services
Where we help
Design systems architecture
We design and scale design systems as product infrastructure, not just component libraries — architecture, governance, accessibility, performance guardrails, and implementation patterns that help teams ship consistent UI faster across products.
Front-end engineering
Senior front-end consulting for audits, modernization, migrations, and complex implementation. We reduce delivery risk by improving architecture, code quality, and accessibility while building durable foundations.
Training & workshops
Practical training for engineering, design, and product teams — design systems, accessible front-end development, and team workflows, tailored to your roadmap. Your teams keep shipping the system long after we're gone.
New guide
How Firefox renders web components
Specs say what should happen; this is what Firefox actually does. Follow a custom element through Gecko's source & step through each stage as an interactive figure.
Read the guide“A walking encyclopedia on CSS, HTML, design systems, & accessibility. One of the best Design Engineers in the business.”
Writing
From the blog
From castastrophe.blog
Building something for the web? Let's talk.
Tell us about your project and goals. We'll figure out how we can move forward together.