If you've ever grabbed a "free proxy list" off GitHub, you already know the feeling: you paste 10,000 IPs into your scraper, and approximately none of them connect. I wanted to know exactly how bad it is, so I measured it.
Short version: of 62,541 free proxies pulled from public lists, only 2,236 (4%) were alive. And "alive" is generous — it just means the TCP handshake completed once.
How I measured it
I built a liveness checker that:
Ingests the big public free-proxy lists on GitHub (the monosans/proxy-list-style aggregators — HTTP, HTTPS, SOCKS4, SOCKS5).
