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

✅ <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>

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.

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