How to extract audio from video | Save MP4 audio as MP3, M4A, or WAV

What does extracting audio from MP4 mean?

MP4 is commonly treated as a video file, but it is a container that can hold video, audio, subtitles, metadata, and other streams.

If meeting.mp4 contains a Video stream and an Audio stream, the audio can be saved separately as a file such as meeting-audio.m4a or meeting-audio.mp3.

The important distinction is that extracting audio and converting audio are not always the same operation. In some cases, the existing audio can be moved into a suitable audio container without re-encoding it.

The difference between extraction and MP3 conversion

When people say they want audio from a video, they often picture MP4 → MP3. In practice there are two main paths: copy the original audio unchanged when supported, or convert it to another audio format.

If the source codec and output container are a verified combination, the selected audio can be extracted without re-encoding. For example, AAC audio inside MP4 can be saved in M4A without encoding the AAC again.

If MP3 or another different format is required, the source audio is decoded and then encoded into the requested format. Because that path re-encodes the audio, settings such as output bitrate can be selected.

1. Choose the video file

Open Video Audio Extractor and choose the source video. On desktop, drag and drop is also supported.

Files such as meeting.mp4, lecture.mov, interview.mkv, or recording.webm can be inspected. Support is not determined by extension alone; FFmpeg examines the container and codecs inside the selected file and inventories its audio tracks.

• MP4 / M4V / MOV
• MKV / WebM
• AVI
• MPEG-TS / MPEG-PS
• FLV
• ASF / WMV
• 3GP and other video containers that the bundled FFmpeg profile can inspect

2. Choose the audio track to extract

A typical phone video often has only one audio track. Movies, recordings, and MKV files can contain several tracks.

When multiple audio tracks are found, choose one using the metadata available in the file, such as language, title, default-track status, codec, bitrate, sample rate, and channel information.

The app processes one audio track per run.

• Language
• Title
• Default-track status
• Codec
• Bitrate
• Sample rate
• Channels

3. Choose how to save the audio

After choosing the track, select the output method. The current options are Keep original quality, M4A, MP3, and WAV.

If you do not need a specific output format, check whether Keep original quality is available first so you can avoid unnecessary re-encoding.

Extract the original audio unchanged

Keep original quality saves supported audio without re-encoding it.

For example, when an MP4 contains AAC audio, the AAC stream can be extracted and saved in an M4A container. The AAC itself is not encoded again.

If the goal is simply to archive the audio without the picture and there is no requirement to standardize on MP3, this path avoids unnecessary conversion.

Save as MP3

Choose MP3 when broad playback compatibility or another application requires it. Available bitrates are 128, 192, 256, and 320 kbps.

You can also choose mono or stereo. Speech-focused material such as meetings or lectures does not always need the highest bitrate, while music may justify a higher setting depending on the intended use.

MP3 encoding uses LAME.

• 128 kbps
• 192 kbps
• 256 kbps
• 320 kbps
• Mono / stereo

Save as M4A

Choose M4A to encode the selected track as AAC. Available bitrates are 128, 192, and 256 kbps.

Extracting existing AAC into M4A without re-encoding and explicitly choosing M4A conversion are different operations.

When the source track is AAC and Keep original quality is available, the AAC can be saved in M4A unchanged. When M4A conversion is selected, the audio is encoded to AAC at the chosen bitrate.

• 128 kbps
• 192 kbps
• 256 kbps

Save as WAV

Choose WAV when you need uncompressed audio that is easy to handle in editing software. The output is 16-bit PCM.

Converting MP3 or AAC to WAV does not improve the original quality. Information already lost during lossy compression does not return, and the WAV file will usually be much larger.

4. Review the output filename

You can edit the output filename before saving. For example, meeting.mp4 may become meeting-audio.m4a.

The extension follows the selected output format, so you only need to adjust the readable basename when necessary.

5. Run Extract audio

When the settings are ready, run Extract audio. The operation uses the bundled FFmpeg WebAssembly in the browser.

The selected video is read locally and the chosen audio track is used to create a new output file. The video is not sent to Browser Kitty for server-side conversion, and the original source file is not modified.

6. Review and save the result

After processing, review the generated format, duration, file size, and other result details. If the browser can play the output format, the result can also be previewed in the app.

Save the audio after checking it. If the browser cannot natively play the generated format, in-app preview may be unavailable even though the file itself was successfully created and can still be saved.

Create another version with different settings

After creating one output, you may want a 320 kbps MP3 instead of 192 kbps or an M4A version from the same video.

Use Change settings and try again to return to the format settings without selecting the source video again.

Extract only the track you need from multi-audio video

MKV and similar files can contain several audio tracks such as Japanese, English, and commentary.

A generic Convert to MP3 action can make it unclear which track will be used. Video Audio Extractor explicitly asks you to choose the target track when several are detected.

This is useful when you want only an English track or another non-default audio stream.

A video that will not play in the browser may still yield audio

Native browser playback and FFmpeg inspection are separate capabilities.

Even if the browser cannot decode the video stream, the bundled FFmpeg build may still parse the container and read the audio track, allowing the audio to be extracted.

Input video preview is not required, so a file that cannot play natively is not automatically unusable for audio extraction.

Large videos still depend on browser and device limits

When the source video is several gigabytes, browser and device limits become important.

Video Audio Extractor mounts the source through WORKERFS and does not begin by copying the entire video into JavaScript memory with File.arrayBuffer().

WASM memory, output size, device performance, browser memory limits, and free storage still matter. Very large or long videos are therefore not guaranteed to succeed, especially on memory-constrained smartphones.

• WASM memory
• Generated audio size
• Device performance
• Memory available to the browser
• Free device storage

Video processing stays in the browser

The workflow from selecting the video through track inspection, extraction or conversion, result review, and saving runs in the browser.

The app CSP uses connect-src 'none', and FFmpeg JavaScript, WebAssembly, and the browser runtime are bundled into the standalone HTML.

The hosted version still has to download the application HTML from Browser Kitty, but the selected video is not then uploaded to a server for audio conversion.

The standalone HTML can be used offline

The repository distributes video-audio-extractor.html as a standalone file containing the required FFmpeg WebAssembly and application code.

Save it and open it directly in a supported browser to inspect video, choose an audio track, extract or convert audio to M4A / MP3 / WAV, and create the result without a network connection.

The source video and generated audio bytes are not stored in LocalStorage.

What happens if you select an audio-only file?

This tool is specifically for extracting audio from video. If you select an audio-only file such as MP3 or WAV, the app reports that it is outside the intended workflow.

To trim an audio file or join several audio clips, use Browser Kitty Audio Cutter & Joiner instead.

What if the video has no audio track?

A video file does not necessarily contain audio. Some files have a video stream but no audio stream at all.

In that case, the app reports that the video has no audio and cannot create an audio output.

Audio editing is outside this tool's scope

Video Audio Extractor focuses on extracting one audio track. It does not trim the middle of the audio, join several clips, add fades, adjust volume, remove noise, apply EQ, or change playback speed.

When those edits are needed, extract the audio first and then use a separate tool such as Audio Cutter & Joiner.

• Trim sections
• Join multiple audio files
• Fade in / fade out
• Volume adjustment
• Noise reduction
• EQ
• Playback-speed changes

Quick workflow: MP4 to MP3

For a straightforward MP4-to-MP3 job, choose the MP4, confirm the audio track, select MP3, choose the bitrate, extract the audio, review the result, and save the MP3.

MP3 bitrate choices are 128 / 192 / 256 / 320 kbps.

Quick workflow: keep the original audio quality

For a supported source codec, choose the video, confirm the audio track, select Keep original quality, and extract the audio. This path does not re-encode the audio into another codec.

If creating MP3 is not itself the goal, check Keep original quality first to avoid an unnecessary conversion.

Save only the audio you need from a video

Extracting audio from video is not limited to simple MP4-to-MP3 conversion.

When the original audio can be kept as-is, it can be saved without re-encoding. Convert to MP3, M4A, or WAV only when that output is actually needed. For multi-audio video, choose the track you want before processing.

Browser Kitty Video Audio Extractor follows a simple flow—choose video → choose audio → choose output method → extract → review and save—without sending the video to an external conversion server.

Tips and limitations

• If you do not require a specific format, check Keep original quality first to avoid unnecessary re-encoding.
• A video that cannot play natively in the browser may still be usable if FFmpeg can parse the container and read its audio track.
• Even without first copying the entire source into JavaScript memory, large files remain subject to WASM memory, output-size, and device-performance limits.
• If the extracted audio needs trimming or joining, process it afterward with Audio Cutter & Joiner.