A/B audio comparator
Load two files and switch between them instantly with the space key or a soft crossfade. Level-matched so the comparison is not decided by volume alone.
How it works and limitations
- Everything happens in your browser: files never leave your device.
- The browser decodes files to PCM; with lossy formats (MP3, M4A) you hear the decoded version, not the original bitstream.
- The “match loudness” option applies up to ±12 dB based on each file's RMS so the comparison is not decided by level alone.
- Both files stay synced by absolute time from the start of each file; there is no content-based alignment.
Built by
Miguel Ángel Colorado Marin (MACM)
Built by
Miguel Ángel Colorado Marin (MACM)
Full-Stack Developer · Guadalajara, España
I develop web apps, digital tools and full projects — from design to deployment.
Comparing two mixes, two masters or two takes of the same recording only works if you can switch without losing aural context: detail memory fades within seconds, and every “load another file” click destroys it. This comparator keeps both audios loaded and synced: press space and you are in the other take at the exact same point; press again and you are back. For subtle differences — a blooming reverb, bass that piles up, compression dulling the attack — the gradual crossfade of up to 500 ms reveals them better than a hard cut, and RMS-based level matching (up to ±12 dB) stops the louder file from sounding “better” just because it is louder. Useful for producers comparing masters, podcasters choosing between two takes of a line, and any decision made on seconds of difference.
Features
- ✓Instant A/B switching with the space key, the button or the X key
- ✓Configurable gradual crossfade from 0 to 500 ms
- ✓RMS-based loudness matching (up to ±12 dB) to compare at the same level
- ✓Both waveforms synced by absolute time, with click-to-seek
- ✓All in your browser: files are never uploaded to any server
How do I A/B compare two audio files?
- 1
Load both audio files
Panels A and B: MP3, WAV, OGG or M4A. Decoded in your browser.
- 2
Play and switch
Space to play/pause; the X key or button switches to the other track without losing position.
- 3
Adjust the crossfade if needed
0 ms for a hard switch, up to 500 ms for a gradual transition.
- 4
Compare at the same level
Enable “match loudness” so RMS levels are evened out and only the sound decides.
Frequently asked questions
Is my audio uploaded to a server?
No. Decoding and playback happen entirely in your browser via the Web Audio API; the file never travels anywhere.
What is A/B testing and what is it for?
It alternates between two versions of the same material at the same playback point; aural detail memory fades within seconds, so instant contrast reveals differences you would miss listening separately.
Why don't my two files sound equally loud?
The files may be mastered at different levels. “Match loudness” measures each file's RMS and applies up to ±12 dB of gain to the quieter one so both play at the same level; disable it to compare original levels too.
Related tools
Embed A/B Audio Comparator on your site
Add A/B Audio Comparator to any web page with a simple iframe. Free, with attribution to miguelacm.es.
<iframe
src="https://miguelacm.es/embed/audio-compare"
width="100%"
height="700"
frameborder="0"
title="A/B Audio Comparator — miguelacm.es"
></iframe>