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

When you set up an internet radio station, your streaming host gives you a stream URL — something like https://stream.yourhost.com:8000/live. But what format is that stream in? And does it matter?

It absolutely matters — especially if you want your station to work on Amazon Alexa, Android apps, smart TVs, and other modern platforms. This guide breaks down the three main internet radio streaming formats in plain English and tells you exactly what each platform requires.

The Three Main Internet Radio Streaming Formats

MP3 (MPEG Audio Layer 3)

MP3 is the oldest and most universally compatible streaming format. Almost every device, browser, and platform that plays audio can handle an MP3 stream. Your Shoutcast or Icecast server likely defaults to MP3 at 128kbps, which is the standard quality for most internet radio stations.

• Bitrates: commonly 64kbps, 128kbps, 192kbps, 320kbps
• Quality: 128kbps is standard (near-CD quality for speech and most music)
• Compatibility: works on virtually everything — Alexa, Android, iOS, Chrome, Firefox
• Typical URL pattern: https://stream.host.com:8000/live (or /stream)
• File extension marker: often /;stream.mp3 or /;

AAC / AAC+ (Advanced Audio Coding)

AAC is a newer, more efficient audio format that delivers better sound quality at the same bitrate as MP3. At 64kbps, AAC sounds noticeably better than 64kbps MP3. This makes it popular for stations that want to offer good quality while keeping bandwidth costs low.

• Bitrates: commonly 32kbps–192kbps
• Quality: AAC at 64kbps sounds roughly equivalent to MP3 at 128kbps
• AAC+: an enhanced version with even more efficient compression
• Compatibility: supported by Alexa, Android, iOS, and modern browsers
• Not supported by some older streaming players

HLS (HTTP Live Streaming / M3U8)

HLS is a modern streaming protocol developed by Apple. Instead of one continuous audio stream, HLS serves audio in small chunks (segments) that the player downloads sequentially. This makes it extremely reliable — if there's a network hiccup, the player can resume without dropping the connection.

• URL format: ends in .m3u8 (a playlist file that references audio segments)
• Adaptive bitrate: can automatically adjust quality based on listener's connection speed
• Compatibility: supported by Alexa, Android, iOS, and most modern platforms
• Increasingly adopted by larger streaming providers like Radio.co and Centova Cast
• Better for mobile listeners on unstable connections

The HTTPS Requirement — Why It Matters

Regardless of whether your station streams in MP3, AAC, or HLS, the single most important technical requirement for modern platforms is that your stream URL starts with https:// (not http://).

Amazon Alexa will reject any stream that is not delivered over HTTPS. Android apps published on the Google Play Store also require HTTPS streams for security compliance. If your stream URL starts with http://, you cannot publish on Alexa or modern Android apps without migrating to HTTPS.

What Format Does Amazon Alexa Support?

Amazon Alexa supports the following audio streaming formats for radio skills:

• MP3 (most commonly used, highly recommended)
• AAC / AAC+ (supported on modern Echo devices)
• HLS / M3U8 (supported on newer Echo devices running Alexa OS 2.x+)

For maximum compatibility across all Alexa devices (including older Echo Dots), an MP3 stream is the safest choice. If you're using HLS, test on multiple Echo device generations before submitting.

What Format Does an Android Radio App Support?

Android's built-in MediaPlayer and ExoPlayer libraries support all three formats natively. A well-built Android radio app will handle MP3, AAC, and HLS streams transparently — your listeners won't notice the difference.

How to Check Your Stream Format and URL

1. 1Log into your streaming host's control panel (Shoutcast, Icecast, Centova, etc.)
2. 2Find your stream URL — it usually looks like https://stream.yourhost.com:PORT/live
3. 3Verify it starts with https:// (not http://)
4. 4Open VLC Media Player → File → Open Network Stream → paste your URL → Play
5. 5If it plays, your stream is working and compatible
6. 6Check VLC's codec information (Tools → Codec Information) to see if it says MP3, AAC, or HLS