Technical Notes

Audio Element Attributes

✅ <audio> element — all standard attributes:

Attribute	Type	Description
src	URL	URL of the audio file (optional if <source> used)
controls	Boolean	Shows browser’s built-in audio controls
autoplay	Boolean	Starts playing automatically when loaded
loop	Boolean	Restarts playback when audio ends
muted	Boolean	Starts playback muted
preload	Enum	Hints to browser about preloading: none, metadata, or auto
crossorigin	Enum	Controls CORS: anonymous or use-credentials
playsinline	Boolean	(iOS Safari) Prevents fullscreen when audio is played
disableRemotePlayback	Boolean	Prevents casting to remote playback devices
class, id, style, title, etc.	Global attributes	Standard HTML global attributes

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✅ <source> element — all standard attributes:

Attribute	Type	Description
src	URL	URL of the media file
type	MIME	Media type (e.g., audio/mpeg, audio/ogg)
media	Media query	Optional: apply only if media query matches
sizes	(unused in audio/video)	Mostly relevant for <img> in srcset
srcset	(unused in audio/video)	Not applicable for <audio> or <video>

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Notes:

• <audio> may use src directly or contain multiple <source> elements.

• <source> elements allow fallbacks and are used in sequence.

• Boolean attributes are true if present, false if omitted.

Blank src

Yes, a <source> element with no src will be safely ignored by all major browsers during media selection.

Behavior:

• The browser processes <source> elements in order.

• If a <source> has no src, it is skipped, even if type is valid.

• This is defined in the HTML spec: the src attribute is required; if missing or empty, the source is considered invalid and ignored.

Example:

<audio controls>
  <source type="audio/mpeg"> <!-- No src, ignored -->
  <source src="audio.mp3" type="audio/mpeg"> <!-- Used -->
</audio>

This is safe and will not cause errors or warnings in any standards-compliant browser.