Low End
    Candy

    Glassbox is the compressor you can see into.

    Free

    Free forever, nothing locked. AU and VST3 on Mac, VST3 on Windows. Name and email, and the download link arrives by email.

    Free forever. No trial clock, no noise bursts, nothing locked. The download link arrives by email. We'll also send a few tips and product emails. Unsubscribe anytime.

    Glassbox compressor interface: split before/after, transfer curve, measured numbers and the coach

    Every number and shape on screen is measured from your own audio while it plays, not guessed.

    See

    Before on the left, after on the right, same window and scale. Rust where it took level away, teal where it gave it back.

    Glassbox interface detail

    Measure

    Short-term LUFS, peak, crest and gain reduction at three timescales, plus a WORKING % for "is this even on?".

    Glassbox interface detail

    Explain

    A live COACH says the most useful true thing right now: nothing's crossing threshold, release is longer than a beat, you're comparing 3 dB louder.

    Glassbox interface detail

    Try the interface

    The real plugin screen. Tap any element for what it does.

    Free, for real

    Free forever

    Glassbox

    Visual compressor

    Free
    • The full plugin, nothing locked
    • AU and VST3 on Mac, VST3 on Windows
    • 17 source recipes and the live coach
    • No trial clock, no noise bursts

    One name and email; the download link arrives by email.

    Main features

    Controls

    • Threshold to −60 dB
    • Ratio to 60:1
    • Attack 0.05 to 250 ms
    • Release 5 to 2500 ms, plus AUTO
    • Quadratic soft knee
    • True lookahead
    • Delay-compensated parallel mix
    • Peak or RMS detector
    • Sidechain HPF and LPF, external, listen
    • Stereo link 0 to 100%, M/S
    • K-weighted auto gain

    What's changing

    • A single transient at full sample resolution, with 30 ms of pre-trigger.
    • Touch a control and the before/after difference lights up and labels itself.
    • Attack and release each light only their own measured slice of the transient.

    Recipes

    • 17 source recipes from kick to master bus.
    • Each one says why those times suit the source and the classic mistake.
    • DIAL IT IN moves the threshold until your audio hits the target.
    • Nine deliberately wrong demo presets to learn from.

    Questions,answered.

    Glassbox

    Is it really free?

    Yes. The full plugin, free forever, nothing locked and no card anywhere.

    How do I get it?

    Enter your name and email and the download link arrives by email. Check spam if it isn't there in a couple of minutes.

    Is it a real compressor or just a teaching toy?

    A real feed-forward, log-domain compressor, using the gain computer and detector from Giannoulis, Massberg and Reiss (JAES, 2012). The curve on screen is drawn by the same function the audio uses.

    Compatibility

    Does it work on Windows?

    Yes, as a VST3.

    Does it work in Pro Tools?

    Not yet. There is no AAX build, so it won't show up in Pro Tools.