MP3 vs. MP4: Comparison and the Main Differences

When I first started editing audio and video files, I assumed MP3 and MP4 were basically the same thing. The names look similar, so how different could they be? It quickly became clear that the two formats behave very differently. MP3 is strictly for audio, while MP4 can carry audio too, but also video, subtitles, images, and metadata all inside one container.

Over time, I’ve used both formats in everyday work. Most of us have used them for things like building playlists, exporting social-media videos. I’ve also done things like recording voice-overs, and archiving old media. What I learned is that choosing between MP4 vs MP3 depends entirely on what you need the file to do. In this guide, I’ll walk you through what MP3 and MP4 actually are, what sets them apart, and how to decide which format makes the most sense for your project.

MP3 is the shortened form of MPEG-1 Audio Layer 3. This is an IEC and ISO standard audio encoding format of 1994 that uses lossy compression. European engineers working on the digital radio research program developed the initial MP3 system in 1991. MP3 was made available for public use in July 1994 with a 13enc encoder. However, the .mp3 filename extension was not introduced until a year later to replace the then .bit extension.

The lossy compression technology that MP3 uses became very popular with the release of the MP3 file system. This is because the compression technology significantly reduces the data for an MP3 audio recording without compromising the audio quality. Compared to audio CDs of that time, MP3s use a psychological trick to achieve small file sizes that use up smaller memory but with better quality output. When someone asks “is MP3 video or audio?” The answer is simple: MP3 is an audio format only, and it has no capacity for video or visual data.

I like to have a rough understanding of what files are doing and how they work. MP3 works by compressing audio in a way that reduces file size without making the sound noticeably worse to most listeners. It uses a technique called lossy compression, which means some parts of the audio signal are permanently removed during encoding. This isn’t done randomly. MP3 relies on psychoacoustic modeling, a method that predicts which frequencies the human ear is less sensitive to. Those sounds are reduced or removed to save space.

When I’ve encoded tracks myself, the difference in file size is dramatic. A high-quality WAV file can easily be 30–40 MB, while the same track converted to MP3 might be only 3–5 MB depending on the bitrate you choose. The lower the bitrate, the more data the encoder removes, and the more noticeable the quality loss becomes. At higher bitrates (like 256–320 kbps), most people won’t hear much degradation unless they’re using studio headphones or listening to very dynamic recordings.

MP3 stores only audio — there’s no space for video, metadata-heavy chapters, or subtitles like in MP4. This simplicity is why MP3 remains so universally supported. Almost anything that can play sound can read MP3 without issues.

I probably wasn’t alone in thinking this was an upgraded generation of file types when I first saw this. They’re actually very different. Whereas MP3 stands for MPEG-1 Layer 3, MP4 stands MPEG-4 part 14. Unlike MP3 files that exclusively store audio content,

​​MP4 is very different from MP3. Rather than being just an audio format, MP4 is a media container or a digital “box” that can hold several streams at once:

• Video
• Audio
• Subtitles or captions
• Still images
• Metadata like chapters or descriptions

This flexibility is why MP4 is the standard for modern video. Most video you see online (YouTube, TikTok, Instagram, personal recordings) is stored in MP4. It can use a variety of codecs, including H.264, HEVC, AAC, ALAC, and many others.

Even though MP4 can store audio-only content, it’s primarily used for video because of its ability to hold multiple synchronized media streams.

MP4 was initially released to the public in 2002 and quickly became popular thanks to Apple's iPod, which played MP4 files. The advent of media players, multimedia, and smartphones sealed MP4 as the default media file type for video content.

Some companies have tried to lessen the confusion caused by MP4 files among users by using different extensions for MP4 files with different data. For instance, Apple decided to introduce .m4a extensions to differentiate MP4 audio files from MP4 video files with extension .m4a. Later on, the technology used in Apple's QuickTime was used to improve the processing time of MP4 files.

When comparing MP3 vs MP4, note that MP4 files and MP4-compatible media have many other classifications with unique extensions that MP4 players will play without a problem. MP4 is the most popular video file format, followed, by far, by Apple's QuickTime (.mov) file format. MP4 files take less disk space because of the compression technology it uses and can be played by pretty much every video media player available.

What is the difference between MP3 and MP4? Whereas MP3 is an audio encoding format, MP4 is a digital multimedia container that can store a range of data, including video, audio, and text. Both MP3 and MP4 files use almost similar technology to compress media and data in a file and make it small in size without deteriorating its quality.

Virtually any media player today will be able to play any MP3 files. However, not all media players – even those that specifically play video - support files of MP4 type. It supports the fact that MP3 has become the default file type for storing audio content in CD quality at about a twelfth the size of the original file. An application must first decompress an MP4 file, then play the extracted media if supported.

MP4 file types, being mere containers for storing data rather than the data itself, offers limited ways of handling the encoded file. This explains why MP4 files did not pick up and become popular the way MP3 files did. Applications that play MP4 files will need to rely on specific codecs (coders and decoders) to determine how the file is encoded and how it should be decoded and decompressed.

Most MP4 files will often have an audio stream of MP3 that plays alongside the content of other formats. For instance, a file may contain a MPEG-4 Part 10 as well as MPEG-4 Part 2 video, MP3 audio, and MPEG-4 Timed Text subtitles. However, because it is merely a container and not a file, MP4 media files can contain sound layers of different formats such as ALAC, TTSI, AAC, SLS, or ALS.

The similarities between MP4 vs. MP3 files extend beyond the name; they are both certified as the International Standard of audio and video formats. The two file systems, however, have significant differences that everyone should know.

I generally remember that the file sizes of MP3 versus MP4 media are usually dependent on the resolution of the media. For instance, with audio MP3 files, the higher the bitrate, the larger the file, and vice versa.

I have found with MP4 files, the higher the video resolution and the sound layer format determines the ultimate size of the file. Better compression means smaller files and better battery time for playback devices and some are compressed more effectively than others.

It isn’t a matter of direct comparison between these two files. I can’t say one is better than another, they each have their own uses. When you listen to podcasts, have a playlist of favorite songs, or even set a ringtone, chances are you use MP3 files. MP3 files are ideal for recording audio files, while movies, video clips, and other motion picture content such as camera recordings can be saved as MP4 files.

MP4, improved with the compression technology used by Apple's QuickTime MOV files, is a versatile media file playable by a majority of media players on all platforms.

Choosing between MP3 and MP4 depends on what the file contains and how you plan to use it.

Choose MP3 if:

• You only need audio
• You want small, lightweight files
• You need maximum compatibility on older devices
• You're storing music, podcasts, or voice recordings

Choose MP4 if:

• The file includes video
• You want one file containing video + audio + subtitles
• You’re exporting content for YouTube or social media
• You need support for modern codecs like AAC or H.264

If you ever need to switch between formats, converters like Movavi Video Converter make the process very simple and straightforward.