In this guide
MP4 is a multimedia container that can hold video, audio and other tracks. A player must support the codecs inside it. Converting its soundtrack to MP3 or WAV creates a separate audio file and does not retain the picture.
An MP4 file is a multimedia file using the MPEG-4 Part 14 container, commonly with the .mp4 extension. It can package video, audio and other information such as subtitles. The container organizes the tracks; the codecs inside determine how the picture and sound are encoded.
For example, an MP4 might contain H.264 video and AAC audio, but the extension does not guarantee that combination. A player must support both the container and the actual codecs. MDN's audio and video guide explains the relationship between a container and its tracks.
Deciding between audio-only MP3 and a media container? Read MP3 vs. MP4 for the practical differences.
MP4 vs. MP3, M4A and WebM
| Name | What it describes | What to check |
|---|---|---|
| MP4 | A container that can hold video and/or audio plus other tracks. | Its video and audio codecs, track selection and destination support. |
| MP3 | A lossy audio codec and commonly an audio-only file. | An MP3 export does not include the video picture. |
| M4A | Commonly an audio-only file using MPEG-4 packaging. | It may use AAC, ALAC or another supported codec; the extension alone does not prove which. |
| WebM | A different media container that can carry video and/or audio. | The actual codec combination and player support. |
See what an MP3 file is, what an M4A file is and what a WebM file is for their specific uses. Renaming a file from .mp4 to .mp3 does not convert its audio or remove its video.
For QuickTime media, see what a MOV file is.
How to open an MP4 file
- Open the local file in a media player or browser that supports its container and codecs. Play the beginning, a middle section and the end to check the file.
- If video plays without sound, check mute and volume, then verify that an audio track exists and the correct track is selected. Some MP4 files have no audio; others can have multiple tracks.
- If the file will not play, check that the download completed and try another compatible player. Use a media inspector to identify its video and audio codecs instead of assuming the extension is enough.
- If a recipient requires a different format, export a compatible copy in a suitable editor and test the result. Keep the original.
If you use FFmpeg tools, ffprobe -show_streams "input.mp4" reports stream information for a local file. Replace the example filename with your path. The ffprobe documentation describes its stream and format reports; it does not repair or convert the file.
Can an MP4 contain only audio?
Yes. MPEG-4 containers can carry audio without a video track, although audio-only files often use an extension such as .m4a. Conversely, a video file may contain no audio. Inspect the tracks in the specific file before choosing a converter or assuming there is a soundtrack to extract.
How to make an MP3 or WAV from MP4 audio
- Open video to MP3 and choose a local MP4 containing audio, up to five minutes and 50 MiB. The browser must support its audio codec, and the decoded audio must be mono or stereo.
- Choose MP3 at 128, 192 or 320 kbps, or choose 16-bit PCM WAV at 44.1 or 48 kHz. The output must also fit 50 MiB.
- Prepare and preview the actual audio, then download it. Check its duration, beginning and ending, and retain the original MP4.
The output contains the decoded soundtrack, not the picture. Speech, music and effects already mixed together remain together. The browser chooses the decoded audio stream; this tool does not select among multiple streams or copy the original encoded audio. MP3 is a new lossy encode, and WAV cannot recover information lost earlier. Resampling or encoding can change samples or timing, and original metadata is not copied.
For a longer file, explicit stream selection or desktop methods, see how to extract audio from video. The separate voice isolator estimates a voice from a mixed recording; it uploads the source and AI downloads require an account and sufficient credits.
Why do two MP4 files have different quality or sizes?
MP4 is packaging, not a fixed quality level. Resolution, frame rate, video and audio codecs, bitrate, duration and source quality all influence the result. A larger file does not necessarily sound or look better, especially if it was re-encoded from a lower-quality source. Compare the same content at the settings required by your destination.
An audio-only estimate is not the size of the full video. The audio file size calculator estimates PCM or fixed-bitrate audio payloads; a video file also contains picture data and container overhead. Check the actual exported file against any upload limit.
Common questions
Is MP4 a video codec?
No. MP4 is a container. H.264 is one example of a video codec that an MP4 can contain; AAC is one possible audio codec.
Is MP4 the same as MP3?
No. MP4 is a multimedia container, while MP3 is a lossy audio encoding and commonly an audio-only file. An MP3 export does not retain the MP4's video picture.
Can I convert an MP4 to MP3 by renaming it?
No. A filename change does not re-encode or extract the sound. Use a compatible converter and check the resulting audio.
Does converting MP4 to WAV improve quality?
PCM WAV can be a useful editing copy, but it cannot restore audio information discarded earlier. Resampling or reducing bit depth can also change samples.