MP3 Converter - Convert Audio to MP3 Online — Turn any common audio file (WAV, FLAC, OGG, Opus, M4A, AAC, WMA, AIFF and more) into MP3 with the bitrate you choose, from 128 kbps up to 320 kbps. An ID3 tag editor is built in: existing tags in the source file are filled in automatically, and you can edit them or add new ones (title, artist, album, album artist, genre, year, track, comment) to embed in the MP3. Everything is processed locally in your browser, with files never uploaded to a server.
Supported input: MP3, WAV, FLAC, OGG, Opus, M4A, AAC, WMA, AIFF and other common audio formats. Everything is converted locally in your browser; files are never uploaded to a server.
First use loads an ~30MB audio processing engine into the current browser. It is cached and reused afterwards, so please be patient.
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Click to select or drag and drop an audio file
Any common audio format; under 500MB recommended
higher = better quality, larger file
MP3 conversion: re-encodes the audio with the LAME MP3 encoder at the selected bitrate. MP3 patents have expired worldwide, so the output is royalty-free.
MP3 ID3 Tags
Fill in any fields below to embed an ID3 tag in the MP3 (fields left empty are omitted). Existing tags in the input file are read automatically and filled in here after you select a file.
What is MP3, and what are ID3 tags?
MP3 (formally MPEG-1 Audio Layer III) is the lossy audio codec that made digital music portable: it shrinks CD-quality audio to roughly a tenth of its size by permanently discarding the parts of the signal your ear is least likely to notice. ID3 tags are the metadata that rides along inside an MP3 file — title, artist, album, genre and so on — so that music players can display what is playing instead of a filename. The two are independent: the codec stores the sound, ID3 stores the description. This converter handles both at once, encoding the audio with the LAME encoder and writing the tag fields you fill in above as ID3v2.
Five facts to anchor the rest of the page:
• MP3 is lossy — discarded audio can never be recovered by re-encoding
• bitrate (kbps) is the quality knob: 128 acceptable, 192 the sweet spot, 320 the maximum for stereo MP3
• a 4-minute MP3 is 3.84 MB at 128 kbps, 5.76 MB at 192 kbps, 9.6 MB at 320 kbps
• ID3v1 = fixed 128-byte footer with 30-character fields; ID3v2 = flexible header, the modern standard
• MP3 patents expired worldwide in 2017 — the format is now royalty-free everywhere
Lossy compression and the psychoacoustic model
MP3 achieves its 10:1 typical reduction with a psychoacoustic model — a model of human hearing that decides what to throw away. Its core tool is auditory masking: a loud sound temporarily makes quieter sounds at nearby frequencies inaudible, so those quiet sounds can be discarded with no perceptible loss. The encoder splits audio into 32 frequency sub-bands, quantises each band just finely enough to stay below the masking threshold, and spends the saved bits on the bands where the ear is most sensitive (roughly 2–5 kHz, where hearing is sharpest). At 128 kbps the encoder also typically low-passes content above about 16 kHz; at 320 kbps it keeps essentially the full audible band.
A naming trap worth clearing up: MP3 is data compression (fewer bytes, permanently less information). A studio "audio compressor" is a completely different tool — dynamic range compression, which squeezes loud and quiet sounds closer together for a punchier mix and has nothing to do with file size.
ID3v1 vs ID3v2
ID3v1 (1996) is a fixed 128-byte block appended to the end of the file: three 30-character fields for title, artist and album, a 4-character year, a 30-character comment, and a genre picked from a numbered list of 80. It cannot hold album art, long titles, or accented characters reliably. ID3v2 solves all of that: it sits at the front of the file, consists of flexible length-prefixed frames, supports UTF-8/UTF-16 text of any length, album art, lyrics, and arbitrary custom fields. One practical difference: because v1 lives at the end and v2 at the front, streaming players can read v2 tags before the whole file arrives. The tag editor above writes ID3v2.3 — the most universally supported version (v2.4 is more capable but some older players reject it).
Bitrate and file size math
MP3 at constant bitrate (CBR) makes size exactly predictable: bytes = kbps × 1000 × seconds / 8. A 4-minute track:
128 kbps — 3.84 MB (0.96 MB per minute); fine for speech or casual listening
192 kbps — 5.76 MB (1.44 MB per minute); transparent to most listeners for most music
320 kbps — 9.6 MB (2.4 MB per minute); the maximum stereo bitrate, still only about a quarter of the 42.336 MB the same track occupies as CD-quality WAV
One consequence of that math: raising the bitrate only helps if the source carries more information than the current file does. Converting a 128 kbps MP3 to 320 kbps produces a 2.5× bigger file that sounds identical to the 128 kbps original.
Common misconceptions
320 kbps MP3 is lossless. No. 320 kbps is still less than a quarter of CD bitrate (1411.2 kbps), and the psychoacoustic model still discards masked content. For true lossless use FLAC or WAV — that is what they are for.
Re-encoding a low-bitrate MP3 at a higher bitrate restores quality. No. Once MP3 discards information it is gone forever; the encoder faithfully preserves the artefacts and adds a new generation of them. Lossy-to-lossy conversion should be done once, at the bitrate you actually want.
ID3 tags affect audio quality. No. Tags are pure metadata displayed by players; deleting or editing every tag leaves the audio samples byte-identical. Fill them in freely — they cost a few hundred bytes and zero fidelity.
