Notes on audio, files and doing it on your own device.
Written and tested by the people who build mp3fy, underfour standing bylines.
Batch convert to MP3: drop a folder, get one ZIP back
Drag a whole folder onto mp3fy to batch convert to MP3: parallel conversion, live per-file progress, one streamed ZIP. On-device, free, no size limits.
Is it safe to use online converters? Convert without uploading
Most online converters upload everything you give them. mp3fy converts to MP3 in your browser instead, with no upload and no limits, and shows how to verify it.
Extract audio from video: MP4 to MP3 in your browser
How to pull the MP3 out of an MP4, MOV, MKV or WebM right in your browser, with no uploads or size caps, plus the size math: an hour of 1080p becomes 86 MB.
FLAC to MP3: keep your tags and cover art intact
Convert FLAC to MP3 on your device and keep every tag and the cover art. mp3fy writes ID3v2.3 with UTF-16, so names like Sigur Rós survive the trip.
The click every thirty minutes: anatomy of a gapless MP3 join
Chunked MP3 encodes plant 50–100 ms of silence at every join. How mp3fy cuts on frame boundaries, trims LAME padding, and rebuilds hours of audio sample-exact.
MP3 vs AAC: which is better and when it actually matters
AAC compresses better; MP3 plays on everything and its patents died in 2017. A full head-to-head comparison, plus when converting to MP3 actually makes sense.
Convert large files to MP3 with no limit: how mp3fy does it
Most converters cap files at 100 MB. mp3fy converts 10-hour recordings and 20 GB videos to MP3 free, with no size limit. Here's the engineering.
WhatsApp voice message to MP3: convert Opus in your browser
Save the .opus file from WhatsApp or Telegram, drop it on mp3fy, and it converts to MP3 in your browser: no upload, no account, names preserved.
Convert audio for transcription: the best format for Whisper
The best audio format for Whisper and most transcription tools: a 128 kbps mono MP3. How to get there from Zoom videos, voice memos and dictaphone files.
Convert an iPhone voice memo to MP3 (M4A to MP3, free)
Share the memo out of Voice Memos, drop the M4A on mp3fy, and get an MP3 in seconds, converted on your device with the title kept and nothing uploaded.
Which MP3 bitrate? 128 vs 192 vs 320 kbps, decided
Pick the right MP3 bitrate in one read: 192 kbps for music, 128 for speech, 320 for archives, plus real file sizes per hour and when 320 actually pays off.
WMA to MP3: rescue your Windows Media library
Browsers can't decode WMA at all, so mp3fy converts it in the cloud: TLS upload, native ffmpeg, deleted the moment it finishes. About 15 seconds per track.