This guide explains how to use Squid Proxies with [cURL](https://curl.se/), a powerful command-line tool used for making HTTP requests. Whether you're testing your proxy pool, performing lightweight API checks, or troubleshooting sessions, cURL is a fast and reliable way to validate proxy connectivity.
## **When to use cURL with Squid Proxies** - Quick proxy validation (before integrating into code) - Checking outbound IP visibility - Inspecting headers and response behavior - Debugging proxy errors (403, 407, timeout, etc.)
## **Proxy authentication methods overview** Squid Proxies supports two authentication methods: ### **1. IP whitelisting** - Add your IP in the dashboard. - Use proxies in the format: `http://proxy_ip:port` ### **2. Username/password authentication** - Use this format in cURL: `http://username:password@proxy_ip:port` 📌 **Tip:** Use the exact proxy address provided in your [dashboard](https://www.squidproxies.com/auth/login?mode=signin) (IP or hostname).
## **Basic proxy setup in cURL** ### **1. IP whitelisted proxies** ```bash curl -x http://123.456.789.10:3128 https://api.ipify.org ``` ### **2. Username/password proxies** ```bash curl -x http://username:password@123.456.789.10:3128 https://api.ipify.org ``` ### **3. Using HTTPS proxies with `--proxy` and `--proxy-user`** ```bash curl --proxy https://proxy.squidproxies.com:8907 --proxy-user username:password https://api.ipify.org ```
## **Verifying IP address and headers** ### **Check if proxy is masking your IP** ```bash curl -x http://username:password@proxy:port https://httpbin.org/ip ``` ### **Inspect full headers** ```bash curl -x http://username:password@proxy:port https://httpbin.org/headers ```
## **Troubleshooting common proxy errors** | Error Code | Meaning | Suggested fix | |--------------|-------------------------------|-------------------------------------------------| | 407 | Proxy authentication required | Check username/password or switch to IP whitelist | | Timeout | Proxy unreachable or blocked | Try a different proxy or test local network | | Empty reply | TLS/SSL or DNS misconfig | Use `--insecure` for testing, check DNS |
## **User-agent and custom headers setup** ```bash curl -x http://username:password@proxy:port \ -A "Mozilla/5.0 (Windows NT 10.0; Win64; x64)" \ -H "Accept-Language: en-US" \ https://httpbin.org/headers ``` You can rotate headers with a script or manually emulate browser behavior.
## **Best practices for cURL proxy usage** - Add `-L` to follow redirects - Use `-v` or `--trace` to debug the request step-by-step - For SSL-heavy testing, add `--insecure` (in non-production tests) - Combine cURL with bash loops to test multiple proxies
## **Bash script example for bulk proxy testing** ```bash #### !/bin/bash while read proxy; do echo "Testing $proxy" curl -x "http://$proxy" -m 5 https://api.ipify.org echo -e "\n---" done < proxies.txt ``` > `proxies.txt` should contain one proxy per line like: > `username:password@ip:port`
## **Key takeaways** cURL is an essential tool for validating and debugging proxy performance with Squid Proxies. Whether you're testing IP visibility, rotating headers, or diagnosing issues, cURL gives you full control over the request pipeline.

📞 Need help with complex testing scenarios? [Contact Support](https://www.squidproxies.com/production-support) — we speak developer.
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**More guides:** - [Proxy rotation & session management](https://www.squidproxies.com/developer-docs/dev-advanced-guides/proxy-rotation-amp-session-management) - [Custom headers & fingerprinting](https://www.squidproxies.com/developer-docs/dev-advanced-guides/custom-headers-and-fingerprinting)