DDMF is a German company that publishes two kinds of audio software: Outstanding signal processors and innovative utilities that no one else makes but should. Plugindoctor is one example of an invaluable tool. I purchased version 1.0 shortly after it was released, and have come to use it regularity.
As the name implies, Plugindoctor will analyze VST2, VST3, and AU plug-ins. With this stand-alone application, simply load the plug-in you want to examine, choose from the various test options, and Plugindoctor will provide details about what's going on with your sound. Do you want to know how a compressor's knee actually turns over? Would you like to test that magic EQ people keep talking about on podcasts? Do you want to verify that one manufacturer's EQ is sonically identical as another's (except for the graphics)? Plugindoctor will show you.
I can hear the cranks in the audience bitching that we should use our ears. To quote Billie Eilish, "Duh!" That's great in theory, however, as the Roman gourmand Apicius purportedly stated, "We eat first with our eyes." Let's face it, we lose our minds (and money) when plug-ins with beautiful GUIs hit the market. It's human nature that we're drawn to attractive products, but it can unduly influence our evaluation. Audio software testing is certainly one area where measurements remain relevant.
I wanted to send a love letter to DDMF. I loaded every Pultec EQP-1A3 emulation I could find. As it turned out, a few were similar, some added harmonic distortion reflecting their reference model, while another imparted a 2 dB curve despite all controls being set to zero.
I strive to restrain my language in reviews, but there are a lot of plug-ins with marketing promises that are complete bullshit. If you want to know which titles I'm referring to, get a copy of Plugindoctor. Don't rely on SSLMonsterMan2000, who has 9,354 posts on that audio forum. Rely on your experiments. DDMF offers a demo and a 30-day money-back guarantee.