I have finally found a HTML (and CSS) validator running on the command line, locally, which actually works and doesn’t want me to pay them money. It appears to work. I already use it.
It’s this one, apparently made by W3: https://validator.github.io/validator/
Each time I run it, it takes a second or so to work. Not that this is a problem — I wait much longer than that for many other programs to do their thing — but it strikes me that nobody has any sense of privacy or security these days, and so maybe this program could be sending my internal, private HTML files (which I ask it to validate) over the network, perhaps because it’s implied that this is just some sort of “interface” program which actually validates it remotely and then sends back the result.
I don’t think so, but you never know. This is why I ask.
The lag is only because it’s running on Java and has to do various processing, is it not? It’s not because it’s sending my data away over the network and waiting for the response?
Before you tell me to “check yourself with Wireshark”, I’ve downloaded that and other similar tools 100+ different times over the last 15+ years and never was able to figure out how to use them, or at least to get any kind of grasp of the traffic passing through my network cable. So maybe it’s easy to you, but it’s not for me.
In fact, I’m 99% sure that it doesn’t send anything away, but I’ve been sure about things in the past and then got a cold shower after I realized that the program in question violated my privacy all along. For example, QuiteRSS actually had Google spyware built into the compiled program and enabled by default, sending Google all my information about which feeds I was subscribing to.