Loudness-matched A/B for two masters

Load two files to compare them at matched playback loudness. The tool measures each file in your browser and turns the louder one down to match the quieter one. No upload or account is required.

Drop file A

WAV, FLAC, AIFF, MP3, AAC. Or click.

Drop file B

WAV, FLAC, AIFF, MP3, AAC. Or click.

Both files stay in your browser. Playback volume changes; the source files do not.

Let your client A/B the same way, then sign off

Let your client compare revisions at matched loudness on a Soneam review link. They can leave comments on the waveform and approve a version without creating an account. Release the finished files on the same link, each with its SHA-256 checksum.

Start free

Why match loudness

Engineers gain-match before comparing plugins or EQ settings for a reason: level differences can affect how you judge the processing. This is that same step, applied to two finished masters instead of two settings.

Measured to the standard

Integrated loudness is computed with ITU-R BS.1770 K-weighting and gating, a standard used for loudness measurement. The louder file is attenuated toward the quieter one, never boosted.

Files stay in your browser

Both files are decoded and played in your own browser. The match is level only, applied with the player's volume, so the audio data is untouched. Nothing is uploaded, so there is nothing here to store.

Free, and no account needed. Put this A/B in front of the client instead of describing it: Fair Loudness is on every review link. What Soneam does.

Fair Loudness FAQ

Why compare two masters at matched loudness?

A difference in playback level can affect which version you prefer. Matching loudness helps you compare changes in tone, balance and dynamics.

What does blind mode do?

Blind mode hides the file names and randomly swaps which button plays each file, so the on-screen position can't tell you which is which. You audition 1 and 2, pick the one you prefer, then reveal to see which file you chose and whether it was the louder one. Hiding the names can reduce the influence of knowing which file is playing.

How is loudness measured in the browser?

Each file is decoded locally and its integrated loudness is measured with ITU-R BS.1770 K-weighting and gating, the same standard streaming platforms use. The measurement runs entirely in your browser; the file is never uploaded.

Does matching loudness change my audio?

The source files are unchanged. The player lowers the louder file’s playback volume without boosting or re-encoding it. Browser and output-device settings can still affect playback.

What files can I compare?

WAV, FLAC, AIFF, MP3, and AAC, as long as your browser can decode them. For mastering comparisons use the lossless files (WAV or FLAC). Both files load from your own machine and play locally.

Is my file uploaded or stored?

No. Both files stay in your browser for measurement and playback. Nothing is sent to a server, so there is nothing on our side to store.