> ## Documentation Index
> Fetch the complete documentation index at: https://docs.responsivevoice.org/llms.txt
> Use this file to discover all available pages before exploring further.

# Events & Callbacks Example

A focused teacher for the speech lifecycle — speak one utterance and watch every public event and per-call callback fire in real time.

> [!TIP]
> [Live demo](https://examples.responsivevoice.org/browser/events-callbacks/) · [Source code](https://github.com/responsivevoice/examples/tree/main/browser/events-callbacks)

## Why a separate example

There are two parallel ways to observe speech: `responsiveVoice.addEventListener(name, fn)` (process-wide, persists across calls) and inline `onstart` / `onend` / `onerror` / `onboundary` callbacks passed to `speak()` (bound to a single utterance). Most confusion in the wild stems from mixing them up. This example surfaces both at the same visual level — a row of per-call pills bound to one utterance, and a row of global pills that fire across the lifetime of the page — so the distinction is concrete instead of conceptual.

## What you'll see

- **Two rows of pills.** The top row (four pills: `onstart`, `onboundary`, `onend`, `onerror`) are the per-call callbacks you pass to `speak()`. The bottom row (nine pills: `OnReady`, `OnVoiceResolved`, `OnStart`, `OnPartStart`, `OnPartEnd`, `OnPause`, `OnResume`, `OnEnd`, `OnError`) are the global events you register with `addEventListener()`.
- **The default text triggers chunking.** The text box starts with a multi-sentence sample long enough that the engine splits it into several parts. Click Speak and you'll see `OnPartStart` show `part X of N` and `OnPartEnd` count up as each chunk finishes.
- **Pills reset on every Speak click**, except `OnReady` — that one fires once when the page loads and stays green for the rest of the session.
- **The full event log sits below the pills.** Once you recognize a pill, you can scroll the log to see the actual data each event carries.
- **`onboundary` only fires for browser-native voices.** When a voice plays through the HTTP fallback (server-side audio), the boundary callback stays quiet and its counter doesn't move.
- **`OnPause` has a \~60-second browser limit.** If you click Pause and don't click Resume within about a minute, the browser cancels the speech automatically and you'll see `OnEnd` fire instead of `OnResume`.

## Next Steps

- [Events Guide](/guides/events) — full event reference and async/await patterns
- [Basic Example](/examples/basic) — minimal `OnReady` + `speak()` flow without the inspection scaffolding