Many friends habitually like to verify once before using the proxy IP, delete invalid and long-delay proxy IPs, keep valid and short-delay proxy IPs, write code to verify, and those who can't write code generally use third-party tools for verification.

When using third-party tools for verification, you will find a problem. Some proxy IPs are valid in this detection tool, but invalid in that detection tool. Why is this?

Some proxy IPs are clearly verified to be valid, but invalid when used. Why is this? The reasons may be as follows:

1. Different verification URLs: Third-party verification tools generally set a simple web page and access this URL by connecting to the proxy IP for verification. Different tools set different URLs. The proxy IP can access this website at a certain time and is considered valid; but it cannot access another website and is considered invalid.

2. Concurrency and delay: When batch verifying the proxy IP list, there are generally two settings: one is the verification timeout, such as 5 seconds. If it exceeds the set timeout, it will be considered invalid; the other is the number of concurrent threads. The larger the concurrency, the faster the verification speed, but it may cause the verification of the proxy IP to be less efficient. The smaller the concurrency, the slower the verification speed, but the verification of the proxy IP may be more efficient.

3. Proxy IP authorization: Generally, high-quality proxy IPs will require authorization. One is to bind the IP whitelist, and the other is to verify the account and password. If the authorization is incorrect, the IP cannot be used at all, and there is no way to verify it. All are invalid.

4. Unstable proxy IP: The proxy IP is valid when verified by this tool, but invalid when verified by that tool. This situation is common in free proxies, ordinary proxies, open proxies, etc.

5. Tool exclusivity: Some tools are designed by proxy service providers, and are only valid for their own proxy IPs. Non-self-owned proxy IPs are invalid. The above are several possible reasons for the inaccurate verification of proxy IPs by third-party verification tools, and there may be other reasons. From this we can see that you should not be too concerned about the accuracy of third-party verification tools for a single IP address. Just use it as a reference.