Which codec should I use for a website?

AAC is the safest default: it plays natively in browsers and across the Apple ecosystem and is better quality per bit than MP3. Choose MP3 only when something genuinely ancient has to open the file, Opus when the audience is on Chromium browsers and speech quality matters most, and FLAC when the file is downloadable lossless rather than streaming.

Why do AAC and ALAC both appear under an m4a container?

Because a container and a codec are different things. The m4a container can hold either the lossy AAC codec or the lossless ALAC codec, and players inspect the container before they try its contents. That is why a device that accepts an m4a file can still fail to play one of the two codecs inside it.

Does the matrix check what my device can play?

No. It is a static snapshot of native support across current browsers and the Apple ecosystem, with no capability detection and no file inspection. Treat it as a planning guide and test on the devices that really matter to your audience.

Is Opus really unsupported on Apple devices?

It is supported from Safari 17 onward, which arrived in 2023, but the matrix lists native support only and lists it as Safari 17+ for that reason. Older Apple software needs a fallback, so if your audience spans a wide range of Apple devices, pair an Opus upload with an AAC or MP3 alternative.

Should I still produce MP3 files in 2026?

Only when something old has to play them. AAC wins on quality per bit and is supported essentially everywhere modern, while MP3 remains the universal fallback and is free of patents as of 2017. For a normal web delivery the AAC row is the better choice, with MP3 kept in reserve for hardware you cannot control.

Codec Compatibility Reference

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Codec Compatibility Reference is a matrix of eight codecs and where each one plays natively, with a separate column for the Apple ecosystem. It answers the delivery question before anything is encoded, which is far cheaper than discovering a problem after a file fails to open.

What is Codec Compatibility Reference?

The rows cover MP3, AAC in an m4a container, Opus, Ogg Vorbis, FLAC, ALAC in m4a, WAV and WMA. Each row states whether the codec is lossy or lossless, whether it plays in browsers, whether Apple platforms support it natively and a note on when it is the right choice. There are no controls to configure; the table is the whole tool.

What each codec is for:

MP3, the universal fallback that plays everywhere but costs size for its quality and has been patent free since 2017.
AAC in m4a, the better quality per bit successor that Apple, YouTube and most browsers treat as the default.
Opus, the strongest quality per bit for speech, native in Chromium browsers and only in Apple software from Safari 17 onward.
Ogg Vorbis, still found inside game engines but best avoided for new web delivery.
FLAC and ALAC, the two compressed lossless options, the first broadly supported and the second an Apple ecosystem choice.
WAV, raw samples with no compression, universally playable, excellent for production and enormous for delivery.
WMA, the legacy Windows format that neither browsers nor Apple platforms play reliably today.

The distinction that drives the whole table is lossy against lossless. MP3, AAC, Opus, Ogg Vorbis and WMA shrink a file by discarding content a psychoacoustic model predicts you will not miss, so their quality depends on the bitrate chosen at encode time. FLAC, ALAC and WAV keep the waveform intact: the first two compress without losing samples and WAV does not compress at all. Container matters as much as codec, because a player inspects the container before it tries the contents, which is why the AAC and ALAC rows both name m4a rather than the codec alone. It is worth knowing which column applies to your audience too: the browser column decides whether a file plays inline on the web, while the Apple column decides whether it opens in iTunes, on iOS or in macOS without a converter, and a row that satisfies both is the safest thing to publish.

What the matrix does not do:

It is a snapshot of native support rather than a live capability check, so it cannot tell you what the device in front of you will accept.
Everywhere means current browsers and operating systems, not every legacy or embedded player.
The Apple column lists native support only, so a codec such as Opus still needs a fallback for older Apple software.
Container support is folded into the rows, and a player that accepts m4a may still reject one of the two codecs inside it.
Nothing here speaks to quality at a given bitrate; the table answers whether a file plays, not how it sounds.
There is no detection step, so the tool cannot identify the codec of a file you drag in.

Read the table as a delivery decision. AAC gives the widest reach at good quality, so it is the sensible default for web audio. Keep MP3 in reserve for genuinely ancient hardware, and choose Opus when the audience is on Chromium browsers and speech quality matters most. Take FLAC for archives and audiophile downloads, and convert WMA on sight, because it is the one row here with no reliable native playback anywhere.

How to use Codec Compatibility Reference

Find the codec you were planning to deliver and read its row across the matrix.
Check the browser and Apple columns together, since a file usually needs to open in both worlds.
Choose the closest supported alternative when a row shows no native playback on the platforms you care about.
Take that decision into a converter; the matrix itself inspects nothing.

When to use Codec Compatibility Reference vs related tools

Codec Compatibility Reference is the check to run before publishing or archiving, when the requirement is that a file opens rather than that it sounds a particular way. Audio Format Converter performs the actual re-encode once the codec is chosen, and the two lossless rows have dedicated homes: FLAC Converter for the broadly supported compressed lossless option and ALAC/M4A Lossless Converter for the Apple equivalent. When the file you have is in the one format with no reliable playback, WMA/M4B/CAF Decoder gets it into something modern.

Privacy & Security

This tool runs entirely in your browser — no data ever leaves your device. There is no server round-trip, no upload, no logging, and no account required. Your input is processed locally using client-side JavaScript and is never stored, transmitted, or accessible to anyone else. When you close the tab, everything disappears.