Format to format
Your provider hands out one format, your software wants another. Paste what you have — the converter reads any of the common field orders and writes back the one you need.
Everything runs in your browser: lists and passwords are never sent anywhere.
There is no standard. Every seller writes lists the way their panel exports them, and every piece of software expects the one its author happened to use. The five shapes that cover almost everything are host:port, host:port:user:pass, user:pass:host:port, user:pass@host:port and a full URL with a scheme (socks5://user:pass@host:port). Browser extensions and anti-detect profiles usually want the colon forms; curl, requests and most libraries want the URL form.
The two four-field colon forms are the trap, because both are four fields separated by colons and they mean opposite things. They are told apart by where the port sits: a numeric field in position two means host:port:user:pass, and a numeric field in position four means user:pass:host:port. When an @ is present the split is made on the last one, not the first — an @ occurs in passwords and never in hostnames, and splitting on the first is the single most common way a converter corrupts credentials.
Nowhere. The conversion runs entirely in your browser: the list is never uploaded, never logged and never leaves the page. This is not a courtesy — a proxy list is a set of credentials, and pasting one into a server-side converter means handing working access to someone you do not know.
A supplier exports host:port:user:pass and your scraper wants a URL with a scheme.
You are loading a list into an anti-detect browser that only accepts one layout.
You need a curl command per proxy to test a handful by hand.
You are moving a pool from one tool to another and want the whole file rewritten rather than edited line by line.
Once the list is in the right shape, find out how much of it is alive with the proxy checker — the format being correct says nothing about the endpoints being up.
Whatever the receiving software documents. As a rough guide: URL form with a scheme for code and command-line tools, colon forms for browser extensions and anti-detect profiles, host:port on its own when authentication is by IP.
No. The conversion happens in your browser and nothing is transmitted or stored. A proxy list contains credentials, so a converter that needed a server round trip would be asking for far too much.
By the position of the numeric field. A port in position two means the host comes first; a port in position four means the credentials come first. It is the only reliable discriminator, because both forms are four colon-separated fields.
An @ is handled by splitting on the last one, since hostnames never contain it. A colon inside a password breaks the colon-separated forms by definition — use the URL form with the password percent-encoded.
No, it only rewrites text. Use the proxy checker for liveness, protocol, country and anonymity; a perfectly formatted list of dead endpoints is still a dead list.
Yes. The scheme is carried through to the URL form, and for the colon forms the protocol is not part of the string at all — it is configured wherever you paste the list.