How to Convert MP4 to MP3

Lectures, courses, and webinars: a 60-minute lecture as 1080p MP4 is 1.5-2 GB; the same audio as 128 kbps MP3 is 56 MB — 30x smaller, easier to share, faster to download for offline listening on a phone. Music videos: extract the song without the video. Podcast video downloads: many shows publish video versions with the audio identical; pulling MP3 from the video is a workaround when the audio-only RSS feed is unavailable. Screen recordings (Zoom, OBS, Camtasia): extract the audio track for transcription, podcast post-production, or sharing the soundtrack alone. YouTube downloads: legal where the content is yours, in the public domain, or licensed for offline use; convert the .mp4 download to MP3. See [extract-audio-from-mp4](/blog/extract-audio-from-mp4) and [how-to-extract-audio-from-video](/blog/how-to-extract-audio-from-video) for related context.

Open [MP4 to MP3](/convert/mp4-to-mp3). Drop the .mp4 file onto the page. The tool runs ffmpeg in WebAssembly locally — your file never leaves your browser, which matters for sensitive content like internal lectures or unreleased footage. The converter demuxes the container (separating audio from video), discards the video track, decodes the AAC audio to PCM, and re-encodes as MP3 using LAME at the chosen bitrate. Default output: 192 kbps CBR, 44.1 kHz, stereo. Click Download. Conversion is bound by audio decoding speed only — typically 5-10x faster than playback, so a 60-minute MP4 finishes in 6-12 seconds on a modern laptop. Free tier: 10-second preview. Pro: full files up to 500 MB.

Match output bitrate to source content and intended use. Voice content (lectures, podcasts, audiobooks): 96-128 kbps mono MP3 — speech needs little; mono cuts another 50%. Music with voice (talk show with intro music, song with vocals): 192 kbps stereo. Pure music: 192 kbps for casual listening, 320 kbps for archival quality. The source audio in MP4 is usually AAC at 128-256 kbps; encoding to MP3 at 320 kbps does not improve quality beyond the source. The encoder cannot invent audio that wasn't there. Practical rule: 192 kbps MP3 from a 256 kbps AAC source preserves all audible content. Going below the source bitrate (e.g., 96 kbps MP3 from 256 kbps AAC source) is double-lossy compression — acceptable for speech, audible for music. See [audio-bitrate-guide-by-use-case](/blog/audio-bitrate-guide-by-use-case).

MP3 is the right output for distribution: universal playback, small files. But for editing or further processing, two alternatives are better. [MP4 to WAV](/guide/how-to-convert-mp4-to-mp3) (use the [MP4 to WAV](/convert/mp4-to-wav) tool) extracts to uncompressed PCM — large files, but bit-identical to the AAC source decoded once, ideal for DAW import where any further processing happens. [MP4 to M4A](/convert/mp4-to-m4a) is technically a remux: the AAC audio inside MP4 is re-wrapped in an M4A container with no transcoding step. The result is bit-identical to the source audio (no quality loss whatsoever) and roughly the same file size as the audio portion of the MP4. M4A is the optimal choice for Apple-ecosystem users; MP3 is the universal-compatibility choice. Decide before converting.

Single file: 'ffmpeg -i input.mp4 -vn -c:a libmp3lame -b:a 192k output.mp3'. The '-vn' flag tells ffmpeg to ignore the video stream entirely, dramatically speeding up the operation. Mono: '-ac 1'. Specific sample rate: '-ar 44100'. Combined: 'ffmpeg -i input.mp4 -vn -c:a libmp3lame -b:a 128k -ac 1 -ar 44100 voice.mp3'. Bit-perfect remux to M4A (no re-encode, fastest, lossless): 'ffmpeg -i input.mp4 -vn -c:a copy output.m4a'. Batch a folder: 'for f in *.mp4; do ffmpeg -i "$f" -vn -c:a libmp3lame -b:a 192k "${f%.mp4}.mp3"; done'. Install ffmpeg via 'brew install ffmpeg' (macOS), 'apt install ffmpeg' (Debian/Ubuntu), or static builds at ffmpeg.org (Windows). ffmpeg also handles .mov, .m4v, .mkv, .webm — the same command works on any video container.

iPhone-recorded videos are MOV by default but the same converter handles MOV identically. For true MP4 files (downloaded from a website, AirDropped from another platform), the workflow is: open Safari, navigate to [MP4 to MP3](/convert/mp4-to-mp3). Tap the upload zone. iOS shows a Files app sheet; tap 'Browse', locate your video file (often in Downloads or wherever it was saved). The converter runs entirely on-device via WebAssembly — surprisingly capable on iPhone 12 and later. After conversion, tap Download; the MP3 saves to Files in your Downloads folder. From there, share via AirDrop, Mail, Voice Memos, or upload directly to a podcast host. iPhones older than iPhone 11 may struggle on files over 100 MB; transfer to a desktop browser for those.

Multiple audio tracks: an MP4 may contain multiple audio streams (commentary track, original audio, separate-language tracks for film). ffmpeg by default extracts the first audio stream. To extract a specific stream: 'ffmpeg -i input.mp4 -vn -map 0:a:1 -c:a libmp3lame -b:a 192k output.mp3' extracts the second audio stream. Use 'ffprobe input.mp4' to list all streams first. Silent output: the source MP4 may be a video-only file (some screen recordings without microphone capture, time-lapse videos). Verify in a player before troubleshooting the converter. HEVC video + AAC audio (modern phone recordings, Netflix downloads): the audio extraction is identical to H.264 sources. DRM-protected content (downloaded movie purchases from old iTunes, HEVC encoded by Netflix): the audio is encrypted alongside the video and cannot be extracted by general-purpose tools. Live-stream-recorded MP4s with fragmented or non-fast-start metadata: ffmpeg handles cleanly; some browser tools may stall — use the desktop ffmpeg path.