Convert MP4 to MP3
Extract audio from any MP4 video and save it as MP3. Free, in your browser, no file uploads.
.mp4 · up to 100 MB
Why use this tool
Extract MP4 audio without uploading your video
Total privacy
Your video never leaves your device. Conversion runs in your browser with FFmpeg.wasm. Zero uploads.
Professional quality
libmp3lame quality 2 — ~190 kbps VBR, the standard for high-quality podcasts and music.
Compatible everywhere
MP3 works in any player, platform, podcast app, or device in the world.
Instant after first load
The FFmpeg engine downloads once and is cached. All future conversions start immediately.
How it works
Three steps, no hassle
Select your MP4 video
Drag or select your .mp4 file. The first time, the FFmpeg engine (~25 MB) downloads and caches — subsequent conversions start instantly.
Audio extraction in your browser
FFmpeg.wasm extracts the audio track and encodes it as MP3 using libmp3lame quality 2 (~190 kbps VBR). Everything runs locally, no server connection.
Download your MP3
Your MP3 file is ready to download. Perfect for podcasts, music, audiobooks, or any personal use.
FAQ
Got questions?
It depends on file size and device performance. A 100 MB video typically takes 30 seconds to 2 minutes. The first time you use the tool, the FFmpeg engine (~25 MB) downloads once and is cached in your browser — subsequent conversions are considerably faster.
Yes. We use libmp3lame quality 2, which produces MP3 in VBR (Variable Bit Rate) mode at approximately 190 kbps average. This setting is virtually indistinguishable from the source audio to the human ear, and is the de facto standard for high-quality podcasts, music, and audiobooks.
The practical limit is determined by your device's RAM, as the file is processed in memory. On most modern computers, files of 100-500 MB can be converted without issues. For very long videos (>1 GB), we recommend a desktop tool like HandBrake or native FFmpeg.
Yes, with some limitations. It works well in Chrome and Edge on Android. On iOS (iPhone/iPad), Safari has memory restrictions that may limit file size; files under 100 MB are recommended on Apple mobile devices. Safari is the best option on iPhone as Chrome on iOS does not have the same WebAssembly access.
DRM-protected videos (such as those from Netflix, Amazon Prime, or Disney+) are encrypted in a way that prevents audio extraction. This tool only works with locally downloaded MP4 files that you have legitimate rights to.
The first time you use any video tool on Convertir.ai, the FFmpeg.wasm engine (~25 MB) is downloaded. This happens only once — the browser caches the engine. All subsequent conversions start instantly, with no re-download required.
MP4 to MP3: the world's most converted media format — MP4 container, MP3 compression, and libmp3lame history
The MP4 format (MPEG-4 Part 14) was published by the Moving Picture Experts Group (MPEG) in 2003 as a multimedia container capable of storing video (H.264, H.265), audio (AAC, MP3), subtitles, and metadata in a single file. Its adoption exploded with the Apple iPod, which in 2004 began selling videos in MP4 format through iTunes. Today it is the standard video container on streaming platforms, social networks, camera recordings (iPhone, Android, GoPro), and video conferencing tools.
MP3 (MPEG-1 Audio Layer III) was developed by the Fraunhofer Institute for Integrated Circuits (IIS) in Germany, with crucial contributions from Karlheinz Brandenburg. The algorithm was patented in 1989 and the MPEG-1 standard published in 1993. The technical key of MP3 is the psychoacoustic model: it removes frequencies the human ear cannot perceive in the presence of other sounds (auditory masking), achieving 10:1 size reductions versus uncompressed audio with minimal perceptual loss. The last MP3 patents expired in 2017, making the format completely free.
Converting MP4 to MP3 is the most performed multimedia file conversion search globally, with over 1.5 million monthly searches. Use cases are countless: extracting the soundtrack from a tutorial video, saving a conference as a podcast, ripping audio from a legally downloaded music video, or converting meeting recordings to lightweight audio for archiving. Convertir.ai uses FFmpeg.wasm with libmp3lame — the same library used by YouTube, Spotify, and Apple Music in their audio pipelines — without your file ever leaving your device.