I've retired my filtering HTTP proxy
I've been using a filter HTTP proxy for a very long time; the last time I looked suggested that I'd been using one for almost as long as they've existed. A couple of years ago, I wrote that it was time for me to upgrade the proxy I was using, because it had last been updated in 1998 and was stuck having only HTTP/1.0 and IPv4. In my usual way of not doing anything about pending issues as long as nothing explodes, I did nothing about the issue since that mid-2016 entry until very recently. When I did start to think about it this January, I decided to take a different course entirely, and I've now retired my filtering HTTP proxy and rely purely on in-browser protections.
Two things pushed me into realizing that this was the only sensible position. The first was realizing that any useful filter on the modern Internet was (and is) going to require frequent updates to filter rules. You can do this with a filtering proxy, but you need to find one that uses trustworthy external filtering rules, imports them regularly, and so on. This can be done, in theory, but I don't think anyone is doing it in practice as a canned thing today, and I believe that all of the good filtering rulesets are designed for in-browser usage these days (for the obvious reason that this is by far the biggest pool of users).
The second is the rapid increase in HTTPS. Back in mid 2016 I saw plenty of HTTP usage living on for a great deal of time to come, but that seems like a much less certain bet today for various reasons. HTTPS usage is certainly way up and there's no filtering HTTP proxy in existence that I would even think about allowing to do HTTPS interception. Browsers have a hard enough time doing HTTPS securely, and they have far more people working to make everything work well and safely than proxy authors ever will. If I want to do filtering for HTTPS traffic, and I do, I have to rely on my browser addons to do it. As more and more sites move to HTTPS, I'm going to have to rely on my browser addons more and more for protection.
In summary, any proxy I used would clearly only be a secondary backup for the real protection of my addons (since it wouldn't protect me from HTTPS and probably wouldn't have rules as good as my addons do). Once I realized all of this, I decided to simplify my life by not using any sort of filtering HTTP proxy, and back at the end of January I turned my old faithful Junkbusters daemon off and de-configured it from my primary Firefox. I don't think I've noticed any particular difference in my browsing, which is probably not a surprise since its filtering rules were probably last updated 20 years ago, like the rest of my Junkbuster install.
(It was throwing away HTTP cookies, but I have other solutions for that now.)
More broadly, it seems clear that the future and even present of filtering is inside the browser, primarily (for now) in browser addons. Filtering proxies are yesterday's technology, used before browsers could do this sort of thing natively. Browser addons is where all the development effort is going, which is why filtering proxy software sees less and less frequent updates (Privoxy was last updated in 2016, for example).
I expected to feel a little sad about this simply because I've run a filtering proxy for so long, but if anything I wound up feeling relieved. Junkbuster's various limitations are things I inflicted on myself voluntarily in exchange for its benefits, but I'm unsentimental about being able to do better now. Still, thanks, little program; I suspect you vastly outlived what your authors expected of you.
(I guess I am just a tiny bit sentimental about it.)