Developers often host auto-updating lists, such as TheSpeedX/PROXY-List or proxifly/free-proxy-list , which can provide thousands of tested proxies in .txt format.
Distributing requests across thousands of IPs to collect data from websites without being blocked. Download 4910x HTTP Proxies List txt
These lists are frequently hosted on open-source repositories and automated aggregator sites: Developers often host auto-updating lists