What is Inertia.js in Laravel?
Why Interviewers Ask This
Senior Laravel engineers are expected to reason about architecture, performance, and edge cases. This question separates mid-level from senior candidates by testing deep system-level understanding.
Answer
Inertia.js is a modern approach to building server-driven single-page applications. It lets you build SPAs with a modern frontend framework (Vue.js, React, Svelte) while keeping all your routing and controllers in Laravel — no separate API needed. Instead of returning JSON from controllers, return Inertia responses: return Inertia::render("Users/Index", ["users" => User::paginate(10)]). The frontend renders Vue/React components with the provided props. Navigation happens without full page reloads via Inertia's client-side adapter. It combines the best of both worlds: server-side routing/auth/validation (Laravel's strengths) with modern reactive frontend components. Laravel Jetstream uses Inertia.js as one of its stack options. Unlike Livewire, UI interactivity is fully in JavaScript.
Common Mistake
Candidates often give textbook answers here. Interviewers are more impressed when you relate the concept to a specific problem you solved in a real Laravel project.