Is this the same audio as the M4A converter produces?

Yes. Both use the AAC codec, so at the same bitrate the sound is the same. The difference is the container: this tool writes a bare stream with no room for metadata, while the M4A tool wraps it in MP4 where tags and artwork have proper fields.

Why do the bitrates start at 96 instead of 64?

Because AAC is efficient enough that 64 kbps is rarely the right answer for music. Its useful range is higher and narrower than MP3's, so the ladder runs from 96 to 256 rather than stretching down to the rates an older codec needs.

Why is there no variable-bitrate option?

The encoder's variable mode is inconsistent between builds and can misbehave on some inputs. Rather than offer a switch that works unpredictably, the tool keeps AAC on constant and average bitrate so results are repeatable.

Will the output keep my cover art?

No. A raw AAC stream has no metadata container, so there is nowhere for artwork or tags to live. Convert to M4A if the labels and pictures need to survive.

Is AAC a good choice for speech?

Yes, it is efficient on speech at low rates, though Opus is better still for real-time voice. For stored speech either is fine, and M4A is usually the friendlier container for a player to open.

AAC Converter

You Might Also Need

M4A Converter

Convert audio to M4A format

OPUS Converter

Convert audio to OPUS format

Bitrate/Quality Converter

Re-encode audio at a different bitrate or quality

Codec Compatibility Reference

Codec compatibility matrix

AAC Converter produces a raw AAC stream, the codec inside most modern streaming and Apple audio, written without a container. It is the target for pipelines that expect a bare stream rather than an M4A file.

What is AAC Converter?

Drop a file, choose a bitrate, and encode. The output is a raw AAC stream with the .aac extension, which is the form some encoders, streamers and command-line tools expect to receive.

The controls:

A bitrate ladder of 96, 128, 192 and 256 kbps, labelled Economy through Best, starting and ending higher than the MP3 ladder.
The shared advanced panel for channel mode, sample rate and metadata.
A reported output size alongside the settings, so the cost of a rate change is visible before the run finishes.

Two things separate this from the M4A tool, and both are about the container rather than the codec. The audio is identical, because both use AAC. What differs is that a raw AAC stream has nowhere to put tags, cover art or chapter markers, so nothing is preserved here even when metadata is set to keep, whereas an MP4 container has real fields for all three. The second difference is the ladder itself: AAC is more efficient than MP3, so 128 kbps AAC is broadly comparable to 192 kbps MP3, which is why the useful range sits between 96 and 256 rather than reusing MP3's 64 to 320. Sizing follows the same arithmetic as any constant rate, roughly a megabyte per minute at 128 kbps, so a one-hour recording lands near 55 MB, while the same hour at 96 kbps takes closer to 42 MB.

The encoder stays on constant and average bitrate (CBR) by design. Its variable mode behaves inconsistently across builds, producing unpredictable results on some inputs, and rather than ship a control that quietly misbehaves the tool leaves VBR out entirely. That makes the output size predictable and the behaviour repeatable between runs, which is the property a streaming or delivery pipeline usually wants anyway. The trade is that material with quiet passages does not get the saving a variable encoder would find.

Because AAC has no in-process encoder here, the job runs through the bundled ffmpeg core, downloaded once and cached by the browser. That is also the path that makes metadata preservation possible for the formats that support it, though a raw stream is not one of them. What you get back is exactly the audio you asked for at the rate you chose, with no level change, filtering or normalisation applied at any point. Speech is where this format earns its place: an interview or a voice note stays intelligible at rates where older codecs begin to smear consonants, and because the bare stream carries no container overhead the figures above describe the whole file, with nothing else attached. If the audio is heading to a phone rather than a delivery pipeline, the M4A tool is the one to reach for instead.

Where it stops:

No tags, artwork or chapters, because a bare stream has no container to hold them.
No variable-bitrate mode, by design.
No lossless output: AAC is always lossy.
One file per run.
Converting from one lossy format to AAC adds a second generation of loss rather than recovering anything.

How to use AAC Converter

Drop an audio file onto the panel.
Choose a bitrate, starting at 128 kbps unless the target device or pipeline says otherwise.
Open advanced settings if the channel mode or sample rate must change.
Convert and download the raw AAC stream.

When to use AAC Converter vs related tools

AAC Converter is the tool for a bare AAC stream, which is what some encoders and streaming setups want to receive. M4A Converter holds the same audio in a container that carries tags and artwork, so it is the better choice for anything a person will play. OPUS Converter is more efficient again at low rates, and Bitrate/Quality Converter changes the rate of an existing file without switching its format.

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.