MP4 to AAC Converter – Free Online

How to Convert MP4 to AAC Online

Drop your MP4 file

Drag and drop your .mp4 file onto the box above, or click Choose Files. The request is already filled in: “Convert this to AAC”.

Say how, if you want

The AI assistant uses sensible defaults. To choose the bitrate, codec or sample rate yourself, say so in the request, for example “Convert this to AAC at 320 kbps”.

Save your AAC file

The assistant opens with your file and converts it on your own device; the file itself is never uploaded. When the AAC file is ready, click Save. Prefer to set everything by hand, or batch-convert several files into a ZIP? The classic converter is one click away on this page.

Why Convert MP4 to AAC?

AAC is the codec that almost every MP4 already uses for sound, so a standalone .aac file keeps the audio in the codec it started in (the converter re-encodes it at the bitrate you set; 100% matches the source). Raw AAC files are handy for HLS packaging, embedded devices and audio pipelines that expect an elementary stream rather than an MP4 container.

If you need a file that plays in iTunes or on a phone, choose M4A instead: it is the same AAC audio wrapped in a container that consumer apps understand. Choose raw AAC for streaming servers and developer workflows.

Private by design: your MP4 file is converted on your own device and never uploaded.
AAC already asked for: the AI assistant's request says AAC, so one drop does it. Want a particular bitrate, codec or sample rate? Just say so.
Batch friendly: the classic converter on this page takes several MP4 files in one go and downloads them as a ZIP.
Free, no watermark: no sign-up, and nothing stamped on the output.

MP4 vs AAC

MP4 (MPEG-4 Part 14): MP4 is the most widely supported video container in the world. It usually carries H.264 or H.265 video with AAC audio, plays on every phone, browser, TV and editing app, and is the safest choice for sharing. It is best for sharing, social media, web playback and mobile devices.

AAC (Advanced Audio Coding): AAC (Advanced Audio Coding) is the successor to MP3 and the codec behind M4A, YouTube and most streaming services. A raw .aac file is an AAC stream without an MP4 wrapper. It is best for streaming, YouTube and modern devices.

In short: keep MP4 when the priority is sharing, social media, web playback and mobile devices, and switch to AAC when the file is headed for streaming, YouTube and modern devices. Need a different target? The full Video Converter supports every format listed below.

MP4 to AAC FAQ

What is the difference between AAC and M4A?

The audio codec is identical. AAC (.aac) is the bare ADTS stream; M4A is that stream stored inside an MP4 container with metadata and seeking support. Most consumer apps prefer M4A.

Which bitrate should I use for AAC?

128 kbps AAC is comparable to 192 kbps MP3 and is fine for speech and casual listening. Use 256 kbps for music you care about.

Is this MP4 to AAC converter free?

Yes. Converting MP4 to AAC on MediaConverter.io is free, with no watermark and no sign-up. The AI assistant runs on a free daily allowance of assistant credits; the classic converter on this page has no daily limit at all.

Are my MP4 files uploaded to a server?

No. The conversion runs inside your browser using FFmpeg compiled to WebAssembly, so your .mp4 file is read and converted on your own device and never uploaded, which keeps private recordings private and means there is no waiting in an upload queue. The AI assistant only sees what you type and basic facts about the file: its name, format, duration and size.

Is there a file size limit for MP4 to AAC?

There is no plan or account limit, but the converter loads the whole MP4 file into your browser's memory, so about 2 GB per file is the practical ceiling; larger files may fail to open. Long or high-resolution files also take longer, especially on phones.

Can I choose the AAC settings myself?

Yes. Ask the AI assistant for a bitrate, codec or sample rate in your request. Audio track selection and every other setting are in the classic converter, one click away on this page.

Will converting MP4 to AAC reduce quality?

AAC is a lossy format, so the MP4 audio is decoded and re-encoded. Keep the bitrate at 100% (or pick 256 to 320 kbps) and the difference is inaudible for almost all listeners.

Which browsers support the MP4 to AAC converter?

It is built and tested on current desktop Chrome and Edge. The conversion itself runs in WebAssembly, which every current desktop browser supports, so speed depends mostly on your computer's processor.