This site has published free SOCKS lists since August 2011. Four drops a day at its busiest, 21 783 lists in total. It went quiet for a stretch, and it is running again with every old page where it always was.
Addresses come from scanning the open internet for hosts answering on the usual SOCKS ports. A candidate is then connected to for real: it has to complete the handshake and fetch a page through itself. Anything that fails either step never reaches the list.
What survives is timed, geolocated and sorted before publishing. Response time is one round trip from Frankfurt, so a distant server can look worse here than it will from where you sit. Uptime is how often that address answered across recent checks, which is the closest thing to a prediction on offer.
Nobody set these up for you. They are misconfigured routers, forgotten test boxes, office equipment with a rule pointing the wrong way. They work because somebody made a mistake, and they stop working when that mistake gets noticed. Half of any list is gone within a day.
That has consequences worth stating plainly. Traffic through a public proxy is visible to whoever runs the box. Do not put a login, a payment or anything private through one. They are fine for checking how a page looks from another country, for scraping something public, for testing geo rules. They are wrong for anything tied to your identity.
Where a task actually needs to hold, the free pool stops being the cheap option. An afternoon spent rebuilding a dead list costs more than private proxies with no traffic cap, and accounts that must look like real subscribers want a rotating mobile IP rather than anything on this page.
Every list published since 2011 is still at its original address. Those pages are snapshots: the addresses answered on the day they went up and have not since. They stay because people linked to them, and a link that leads nowhere helps no one. Each carries a note saying how old it is and a way back to the current list. Browse it by month in the archive.
The proxy checker takes a pasted list and tests it the same way the published lists are tested. Use it on anything from here that has been sitting in a text file for a while.
If an address on this site belongs to you and should not be public, write in and it comes off, no questions and no argument. Details on the contact page.