Error Model

dash.js distinguishes strictly between runtime errors and API misuse.

Runtime errors are events

Anything that goes wrong during playback — manifest download failures, segment timeouts, DRM key errors, capability mismatches — is dispatched as a DashJSError object via the public ERROR event. The player never throws for runtime problems:

player.on(dashjs.MediaPlayer.events.ERROR, (e) => {
    console.error('code', e.error.code, 'message', e.error.message, e.error.data);
});

A DashJSError carries a numeric code, a human-readable message and an optional data payload with context.

Error code families

Family	Defined in	Examples
Core/download errors	src/core/errors/Errors.js	manifest parsing/loading failures, xlink failures, segment index errors
Protection errors	src/streaming/protection/errors/ProtectionErrors.js	key session, license request and server certificate errors (codes 100+)
MSS errors	src/mss/errors/MssErrors.js	Smooth Streaming specific failures
Offline errors	src/offline/errors/OfflineErrors.js	download/storage failures for offline playback

All error classes extend ErrorsBase; the constants are exported on dashjs.MediaPlayer.errors, so applications can compare codes symbolically:

player.on(dashjs.MediaPlayer.events.ERROR, (e) => {
    if (e.error.code === dashjs.MediaPlayer.errors.MANIFEST_LOADER_LOADING_FAILURE_ERROR_CODE) {
        // manifest could not be loaded — maybe retry with a backup URL
    }
});

API misuse throws synchronously

Calling MediaPlayer methods in an invalid state — for example before initialize(), or preload() before attachSource() — throws immediately with a descriptive error such as MEDIA_PLAYER_NOT_INITIALIZED_ERROR or SOURCE_NOT_ATTACHED_ERROR. The same applies to invalid argument types: setters validate their input and throw Constants.BAD_ARGUMENT_ERROR style errors synchronously.

Rule of thumb: if the problem is your code, dash.js throws; if the problem is the stream, the network or the platform, dash.js dispatches an ERROR event.