The end-to-end quality of how a developer interacts with a product, platform, or API — from first docs read to first successful deploy to ongoing maintenance. DX is to developer tools what UX is to consumer products: the compounding moat that decides whether anyone recommends you. For FeatureOS, developer experience matters at the embed widget, webhooks, and API surface — these are the details that determine whether a PM's engineer smiles or curses when wiring it in.