Extracting audio from a video is one of the most common file conversion tasks — and one of the most misunderstood. Many people think you need a specialised audio tool or a subscription service to pull the audio out of an MP4. You don't. The audio track in an MP4 file is just data sitting inside a container alongside the video track. Separating it is fast, lossless in some cases, and completely doable in your browser without uploading your video file anywhere.
MP3 vs WAV: Which Output Should You Choose?
Pick based on what you're doing with the audio next:
- MP3: Best for listening, sharing, podcasting, and uploading to platforms. Files are 3–10 MB for a typical 5-minute track. Every device and app on earth plays MP3. The tradeoff is lossy compression — some audio data is permanently removed during encoding.
- WAV: Best for professional audio editing, music production, and any workflow where you'll be processing the audio further. WAV is uncompressed — files are large (around 50 MB per 5 minutes at CD quality), but every single detail of the original recording is preserved. Import into Audacity, Logic Pro, Pro Tools, or any DAW without any quality concerns.
- Quick rule: if you're listening, pick MP3. If you're editing, pick WAV.
How to Extract MP3 from an MP4 Video
Convifi pulls the audio out locally — your video file doesn't go anywhere. That matters when the content is a meeting recording, a consultation, or anything else that's not meant to live on a server.
- Go to convifi.com/convert/mp4-to-mp3
- Click "Select File" and choose your MP4
- The tool uses the Web Audio API to decode the video's audio stream
- The MP3 is encoded locally using WebAssembly (lamejs)
- Download the resulting MP3 file
How to Extract WAV from an MP4 Video
WAV extraction follows the same process at convifi.com/convert/mp4-to-wav. WAV files are significantly larger than MP3, but if you need raw, uncompressed audio for editing — or if you're sending audio to a studio, broadcaster, or sound engineer — WAV is the professional standard.
Does Extraction Affect Audio Quality?
It depends on the output format. When extracting to WAV, the audio is decoded from the video's compressed audio stream (usually AAC) and written as uncompressed PCM. This is not perfectly lossless — you're uncompressing the already-compressed AAC audio — but the quality is exactly what was in the original video. No additional degradation occurs. When extracting to MP3, the audio goes through a second compression step (AAC → PCM → MP3), which introduces a small additional quality loss. At 192 kbps or higher MP3 bitrate, this loss is imperceptible on consumer headphones. At 128 kbps, there may be very subtle differences on high-end equipment.
Common Use Cases
People do this for all sorts of reasons:
- Grabbing the audio from a music video to add to a playlist
- Archiving a conference talk, webinar, or lecture as a lightweight audio file
- Extracting narration from a screen recording for use in a different video project
- Getting the soundtrack from a movie clip for use as background music in a presentation
- Saving a song performed at an event that was recorded on someone's phone
- Transcribing the audio from a meeting recording using a transcription service
Batch Audio Extraction
The browser tool handles one file at a time. If you need to extract audio from dozens of MP4 files, a command-line tool is more efficient. On Mac or Linux: ffmpeg -i input.mp4 -q:a 0 -map a output.mp3 extracts the audio track at the best available quality. On Windows, you can install FFmpeg and run the same command in PowerShell or Command Prompt.
ffmpeg -i input.mp4 -q:a 0 -map a output.mp3Extracting Audio from Other Video Formats
The same approach works for MOV, MKV, AVI, and WebM files. Each has its own converter on Convifi:
- MOV to MP3: convifi.com/convert/mov-to-mp3 — ideal for iPhone recordings
- MKV to MP3: convifi.com/convert/mkv-to-mp3 — ideal for extracting movie soundtracks
- WebM to MP3: convifi.com/convert/webm-to-mp3 — ideal for downloaded web videos and screen recordings
- AVI to MP3: convifi.com/convert/avi-to-mp3 — ideal for old camcorder recordings
What About Copyright?
Extracting audio from video you own or have rights to is completely legal. Extracting audio from copyrighted music videos or commercial content for distribution is a different matter — check the content's license before sharing extracted audio publicly.