About
Learn frontend systems by running them
Frontend Systems Lab is an interactive learning and experimentation platform for frontend developers and engineers.
Why this exists
Documentation explains what a system does. Articles explain what someone else observed. Neither lets you change an input and watch the consequence.
Each lab follows the same loop: concept, interaction, observation, measurement, explanation, understanding. The layout is deliberately identical across experiments so the only thing that changes is the system under test.
Every experiment runs real browser behaviour in your own tab. The numbers you see are measured while you interact, not scripted, and the explanations describe what you just observed.
Explore LabsPrinciples
Interaction before explanation
Every lab starts with something you can change. The prose comes after you have seen the behaviour.
Measure, don't assert
Where a claim can be measured in the browser, the lab measures it and shows the numbers.
Local-first, no account
Progress, bookmarks and experiment settings are stored on your device. Nothing is required to use the product.
The product is the case study
The platform itself is built to the performance and accessibility standards it teaches.