---
title: "V3 app bootstrap constraints"
description: The four constraints every V3 boot HTML must satisfy. Covers Fliplet.require.lazy for dependencies, Fliplet.Media.getContents for source files, the Fliplet().then(...) init sequence, and the locked viewport meta. Framework-agnostic.
type: guide
tags: [js-api, v3, bootstrap]
v3_relevant: true
deprecated: false
---
# V3 app bootstrap constraints
A V3 app is a single HTML boot page that hosts the whole SPA. The page can use any framework (Vue, React, Svelte, vanilla JS, etc.), but it **must** satisfy four constraints so the Fliplet runtime, dependency loader, media authentication, and native shell work correctly.
Each constraint maps to a concrete platform guarantee:
1. Dependencies resolve through the Fliplet asset pipeline so versioning, caching, and per-environment injection work.
2. Source files are fetched with signed media requests so private apps don't leak their screens.
3. The runtime registers its globals (`Fliplet.ENV`, `Fliplet.Router`, `Fliplet.Session`, etc.) before your framework mounts.
4. The viewport is locked so native apps don't pinch-zoom or auto-zoom when users focus an input field.
Skip any of these constraints and the app fails at boot, works in dev but breaks in production, or is rejected by the boot-HTML lint.
## 1. Fetch dependencies with `Fliplet.require.lazy`
Any registered Fliplet dependency (Vue, React, Vue Router, etc.) **must** be loaded with `Fliplet.require.lazy(name)`. Never use `