# Introduction

> What Switchbox is, how it's delivered, and when to use it.

Switchbox is a feature flag service with an unusual delivery model: your flag
configuration is published as a **static JSON file on a CDN**, and our SDKs read
it directly from the edge. There is no API server in the read path. Your app
fetches a small file from Cloudflare, caches it, and evaluates every flag
**locally, in-process, in under a millisecond**.

That one design choice is the whole product:

- **Your app never waits on us.** Flag checks are a local lookup against a cached
  config — no network call per evaluation, no added request latency.
- **If we're down, you keep working.** The SDK serves the last config it fetched.
  There is no hard dependency on a live API.
- **It scales like a CDN, because it is one.** Reads are static-file GETs on
  Cloudflare's edge, not database queries.

## When to use Switchbox

Switchbox fits the common cases that feature flags are built for:

- **Ship dark, release later** — deploy code with a feature flagged off, flip it
  on when you're ready.
- **Gradual rollouts** — release to 5% of users, watch your metrics, then ramp.
- **Targeting** — turn a feature on for a plan, a country, an internal team, or
  any attribute you pass in.
- **Kill switches** — toggle a misbehaving feature off from the dashboard without
  a deploy.

It is **hosted-only** — there's no self-hosting story. You manage flags in the
dashboard; your app reads them through one of the SDKs.

## The two halves

There are two surfaces to learn, and they're small:

1. **The dashboard** (`switchbox.dev`) — where you create projects, environments,
   and flags, set targeting rules and rollouts, and rotate SDK keys. This is the
   only place flags are *written*.
2. **The SDKs** — [Python](/docs/sdk/python),
   [JavaScript](/docs/sdk/javascript), and [React](/docs/sdk/react). These *read*
   the published config and evaluate flags in your app. They share one evaluation
   engine, so a given user gets the **same** result in every language.

## Next steps

- **[Quickstart](/docs/quickstart)** — go from signup to a live flag in under five
  minutes. Start here.
- **[How it works](/docs/concepts/how-it-works)** — the CDN read path, local
  evaluation, and polling, explained.
- **[SDK reference](/docs/sdk/python)** — every method, option, and behaviour for
  each SDK.