Internet Radio Streaming Formats Explained: MP3, AAC, HLS & What Alexa Requires

Most station owners never chose their stream format — a hosting plan came with defaults, and that was that. Then they try to get on Alexa or build an app, and suddenly the format matters very much: a stream that plays beautifully in a desktop browser can be completely invisible to an Echo device. The good news is that the format landscape is small — three formats, one hard rule about security, and a quick way to check what you have.

MP3: The Universal Default

MP3 is the oldest streaming format still in wide use, and its superpower is compatibility: everything plays it. Every Echo generation, every Android phone, every iPhone, every browser, every car system, every radio app built since streaming existed. A Shoutcast or Icecast server nearly always defaults to MP3, usually at 128kbps — the bitrate most of the internet radio world has standardized on for years.

• Typical bitrates: 64kbps (talk/low quality), 128kbps (the standard), 192–320kbps (high quality, heavy bandwidth)
• 128kbps MP3 is the safe default for music stations — near-CD for most listeners on most speakers
• Works on literally every platform that plays audio

AAC: Same Quality, Less Bandwidth

AAC is the more modern codec: at the same bitrate, it sounds better than MP3. AAC at 64kbps lands roughly where MP3 at 128kbps does, which is why bandwidth-conscious stations use it — half the data for equivalent perceived quality. The trade-off is history: a handful of very old players and car units choke on it. Those are vanishingly rare in 2026, but they exist.

• Supported by Alexa, Android, iOS, and all modern browsers
• AAC+ (HE-AAC) squeezes even more quality out of low bitrates — good for 32–64kbps streams
• The right choice when bandwidth costs are the constraint

HLS: The Modern Standard

HLS (HTTP Live Streaming) works differently — instead of one continuous connection, the stream is cut into small chunks the player fetches one after another via plain HTTPS. If the network hiccups, the player just grabs the next chunk instead of dropping the whole connection. This is why HLS is noticeably more reliable on mobile networks, why Apple built it, and why modern platforms — Radio.co, Zeno.FM, Live365 — use it as their default. An HLS URL ends in .m3u8.

For a station owner, HLS has one especially useful property: it rides on standard web ports and standard HTTPS, so it slips past the port-blocking and carrier filtering that sometimes breaks old-style streams on mobile data.

What Alexa Actually Accepts

Three formats, nothing else: MP3, AAC, and HLS. The exclusion that bites people is OGG Vorbis and Opus — the default on many Icecast and AzuraCast setups. A station streaming OGG plays fine in VLC (VLC plays everything) and is completely silent on every Echo. If your stream is OGG, you need an MP3 or AAC mount point for anything smart-speaker shaped.

For maximum device coverage, MP3 is still the safest single choice. HLS is the future-leaning choice if your host offers it.

The HTTPS Rule That Overrides Everything

Whatever format you choose, the stream must arrive over HTTPS for Alexa or a Play Store app. This isn't about quality or compatibility — it's Amazon's and Google's security requirement, enforced at certification, with no exceptions. An HTTP stream is the single most common reason a radio submission fails.

Checking What You Have

1. 1Open VLC → Media → Open Network Stream → paste your URL → play
2. 2It plays? Good — the stream is up.
3. 3Tools → Codec Information — this tells you the actual format: MP3, AAC, or HLS
4. 4Look at the URL you pasted: https or http

That's the whole landscape. If your check comes back MP3 or AAC over HTTPS, you're compatible with everything that matters. If it comes back OGG or HTTP, you now know exactly what to fix — and it's usually one conversation with your host.