Equalizer APO: Free Open-Source System-Wide EQ for Windows

Have you ever installed an equalizer, loaded a preset from Reddit, and heard exactly the same sound as before?

Equalizer APO is a free, open-source equalizer that changes the sound of every application on a Windows PC at once: Spotify, YouTube, games, browsers and Discord. It runs on Windows from Vista through Windows 11, and the current release is v1.4.2.

Why Equalizer APO?

Most consumer equalizers give you 5 or 10 fixed sliders. Equalizer APO has no filter limit. For each filter you choose the center frequency, the gain in decibels and the Q, which sets how wide the adjustment is.

It also runs VST plugins system-wide, reads Room EQ Wizard files for room correction, and handles stereo, 5.1 and 7.1 layouts. Config changes apply within about a second of saving the file, so you can tune by ear while music plays.

How to use Equalizer APO

The setup has 6 steps, and steps 2 and 5 decide whether it works.

1. Download the build for your PC from the SourceForge project. x64 suits almost everyone. x86 is for 32-bit machines, and ARM64 is for Snapdragon laptops.
2. Run the installer. SmartScreen may warn about an unknown publisher, which is expected for an open-source project without a paid code-signing certificate. Click More info, then Run anyway.
3. In the Device Selector, tick the device you actually listen on. If you wear headphones and tick your laptop speakers, nothing changes in your ears.
4. Let the Device Selector run its installation test, then restart. The audio service has to reload before the driver attaches.
5. Open config.txt in C:\Program Files\EqualizerAPO\config, set the first line to Preamp: -15 dB, save, and play music. If the volume drops, it works. If nothing happens, it is attached to the wrong device.
6. Optionally install Peace, a free interface by Peter Verbeek that adds sliders, a live graph and presets.

My first install sat on the wrong audio device for 2 days while I blamed the presets. The preamp test in step 5 takes 60 seconds and would have caught it.

Performance

In a loopback test, averaged over 10 runs, Equalizer APO added 0.2 to 0.3 ms of latency. Even a 6-filter preset kept total latency under 3 ms. CPU use stayed under 1% on a modern processor, so it won't cost you frames in a game.

Works below your applications

APO stands for Audio Processing Object, Microsoft's term for code that plugs into the Windows audio stack. Equalizer APO sits inside that pipeline, below your applications, which is why one config file covers everything that plays through the normal Windows audio engine.

The same design sets its limit. Apps that bypass the audio engine bypass the equalizer too. That covers ASIO programs and players set to WASAPI exclusive mode.

Writing your first config

The config file is plain text, read top to bottom, and anything after # is ignored. This example adds bass without the mud:

Preamp: -6.5 dB # headroom for the 6 dB boost below

Filter 1: ON LSC Fc 105 Hz Gain 6.0 dB Q 0.70 # lift everything under 105 Hz

Filter 2: ON PK Fc 250 Hz Gain -2.5 dB Q 1.20 # remove the boom

Filter 3: ON PK Fc 3000 Hz Gain 1.5 dB Q 1.00 # keep vocals audible

PK is a peaking filter and LSC is a low shelf. Boosts can clip and cuts can't, so lower the preamp by roughly the size of your largest boost.

Where it stops working

• Windows feature updates can detach it from your audio devices. Reopen the Device Selector, tick your device again and restart.
• Equalizer APO has no per-app EQ.
• On Windows 11, Bluetooth headsets need the Hands-Free profile disabled, which also disables the headset microphone for calls.

License

Equalizer APO is free and open source under GPL v2. Jonas Thedering wrote it, and the project has been on SourceForge since 2012. The installer is 11.4 MB, with no ads and no bundled software. Some antivirus tools flag it because it installs an audio driver, so compare the file's SHA-256 hash before running it.

Conclusion

Equalizer APO gives Windows a full parametric equalizer at no cost. The built-in editor is a text file, and Peace softens that for most users. Ready-made presets for headphones, laptop speakers, FPS games and dialogue are collected in an independent guide at https://equalizerapoguide.com/. It is not affiliated with the developer, and its author reports testing every step on Windows 11 24H2 in 2026.