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WAV, MP3, M4A, AAC, OGG, FLAC, or WebM audio. One file at a time.
{{ sourceFile ? sourceFile.name : 'Drop audio here or browse' }}
{{ sourceFile ? sourceFileSummary : 'Your source never leaves this device' }}
{{ processing ? `Converting locally · ${processingProgress}%` : sourceStatus }}
The generated one-second WAV is safe for testing the full workflow.

Ignored {{ ignoredFileCount }} extra {{ ignoredFileCount === 1 ? 'file' : 'files' }}. This tool converts one file at a time.

Compatible streams are copied when possible; other inputs use a reviewed preservation-first profile.
Conversion begins only after this action and runs locally.
{{ downmix_mono ? 'Mono output' : 'Preserve mono or stereo' }}
Off is neutral: mono stays mono, stereo stays stereo, and wider layouts use stereo.
Converted audio
Review {{ outputLabel }} playback
Revision {{ outputRevision }} · {{ outputCodec.toUpperCase() }} · {{ formatSampleRate(outputSampleRate) }} · {{ outputChannels === 1 ? 'Mono' : 'Stereo' }}
{{ outputMode === 'copy' ? 'Stream copied' : 'Re-encoded' }}

The chart renderer is unavailable. The same rates remain available in the conversion ledger.

CheckpointSourceOutputMeaningCopy
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Audio File Size Calculator Estimate audio file and session storage from PCM settings or encoded bitrate with multitrack counts, media-fit checks and a planning buffer.
Decibel Calculator Convert pressure or power ratios to decibels and solve dB levels back to voltage or amplitude quantities with fixed and custom references.
Tap-Tempo Beats Per Minute (BPM) Calculator Tap a rhythm to estimate quarter-note BPM, compare instant and rolling tempo, and judge timing stability from jitter and drift.
Tempo Generator / Metronome Set a metronome pulse and build a bounded practice ramp with tap tempo and swing timing plus beat-duration tables and local audio playback.

An audio filename does not fully describe what is inside it. MP3, M4A, FLAC, and WAV name common delivery formats, but playback also depends on the encoded sound, sampling frequency, channel layout, and the features a receiving app understands. Format conversion is therefore a compatibility decision, not just an extension change.

Container or file format
The outer structure that stores the audio stream and supported tags. M4A, WAV, and FLAC each have different storage rules.
Codec
The method used to represent the sound, such as MP3, AAC, FLAC, or pulse-code modulation (PCM).
Sample rate
How many samples describe one second of audio, measured in hertz. A higher number is not an automatic quality improvement after recording.
Channels
Separate audio signals such as mono or stereo. Reducing channels changes the mix and cannot be undone from the converted copy.

Lossy formats such as MP3 and AAC remove information to reduce size. Converting one lossy stream into another creates a new approximation, so repeated conversions can make artifacts more noticeable. FLAC preserves decoded sample values with compression, while WAV stores uncompressed 16-bit PCM in this workflow and can be much larger.

Copying an already compatible encoded stream is different from re-encoding it. A stream copy avoids another lossy generation, but it is possible only when the source codec, sample rate, and channel count already match the destination profile. Any required rate cap, mono mix, channel reduction, or codec change requires decoding and re-encoding.

Choose the destination for its real job. MP3 suits broad playback, M4A carries AAC for many modern players, FLAC is useful when lossless compression matters, and WAV is useful when simple uncompressed PCM is required. Keep the original when later editing, mastering, or archival fidelity matters.

How to Use This Tool:

Choose the format required by the receiving player or workflow, then leave channel handling unchanged unless mono is an explicit requirement.

  1. Add one Source audio file in WAV, MP3, M4A, AAC, OGG, FLAC, or WebM form. The file must be audio-only, no larger than 25 MB, and no longer than 10 minutes.
  2. Select Target format. Use MP3 or M4A for lossy compatibility, FLAC for lossless compression, or WAV for uncompressed 16-bit PCM.
  3. Open Advanced and enable Channel handling only when the destination needs mono. With it off, mono and stereo are preserved, while wider layouts are reduced to stereo.
  4. Start conversion, then play the result and inspect the conversion ledger. If the browser cannot decode the source codec or start the requested encoder, choose a different source or target rather than renaming the file.

Interpreting Results:

First listen to the converted audio. Check speech clarity, music transients, stereo placement, and the beginning and end of the recording. A successful structural check cannot decide whether a lossy result sounds good enough for its audience.

Stream copied means the encoded frames already matched the target codec, sampling frequency, and channel plan. Re-encoded means decoded sound was encoded again, so quality and size can change even when duration is preserved.

Use the ledger to confirm the actual codec, sample rate, channel count, duration, and file size. FLAC or WAV can be larger than a compressed source without indicating a failure; their purpose is lossless or uncompressed output, not guaranteed byte reduction.

Technical Details:

Audio conversion starts by identifying the primary audio track and rejecting video-bearing containers. The destination profile then decides the codec, container, highest permitted sample rate, channel count, sample representation, and lossy bitrate. Supported tags are passed through only when the destination can store them.

Rule Core

The output channel count is one when mono downmix is selected. Otherwise it is the source channel count capped at two. Output sample rate is the lower of the source rate and the target profile limit.

Target Codec and container Maximum sample rate Re-encode profile
MP3 MP3 in an MP3 file 48,000 Hz 128 kbit/s mono or 256 kbit/s stereo
M4A AAC in an ISO base media file 48,000 Hz 96 kbit/s mono or 192 kbit/s stereo
FLAC FLAC in a FLAC file 192,000 Hz Lossless, 32-bit sample representation
WAV 16-bit PCM in a WAVE file 192,000 Hz Lossless, uncompressed 16-bit samples

A stream is copied only when source codec equals target codec, source channels already equal output channels, and source sample rate already equals output sample rate. In that case the source bitrate and sample representation are retained. Every other accepted path is re-encoded with the profile above.

Transformation Core

Stage Decision Failure that stops the result
Inspect Read duration, codec, sample rate, channels, and average bitrate from one audio track. Unrecognized signature, unreadable media, missing audio, or a video track
Plan Choose stream copy or re-encode from the exact codec, rate, and channel match. Source codec cannot be decoded for a required re-encode
Convert Copy compatible frames or decode and encode the requested profile; discard video and preserve supported tags. Target codec or track layout is unavailable in the browser
Verify Reopen the output and measure its codec, duration, sample rate, and channels. Wrong codec, wrong rate or channels, video present, or duration difference above tolerance

Duration may differ by no more than 0.15 seconds or 2% of the source duration, whichever is larger. Download becomes available only after the generated file reopens as audio-only media and all profile checks pass.

Privacy Notes:

The source is read and converted locally in the browser, not uploaded to an audio-conversion service. Supporting code may need to load before the selected codec can run.

  • Only metadata supported by the destination can survive conversion, so inspect the new file before relying on tags such as title or artist.
  • Clear the page or close the tab after handling private recordings.
  • Keep the source until playback and downstream compatibility have been confirmed.