Free Online Proxy Checker Tool

How we check proxies

Our checker is best in class. We don’t just tell you whether a proxy works — we fully diagnose the connection, from your device to the proxy and through the proxy to test sites, as close as possible to real-world usage. You’ll see the status at every stage of the TCP connection. The result is an honest, reliable report with latency metrics and actionable recommendations, without having to visit third-party sites, risk data leaks, or get false “proxy not working” messages caused by poor checkers.

Alive status

Check your proxy: online or offline

In this test, we check whether the proxy is accessible from our server. We attempt to test both protocols — HTTP and SOCKS5.

Internet connections pass through many intermediate nodes, so sometimes the proxy itself works, but the connection is interrupted somewhere along the way. This can be caused by a firewall, incorrect routing by the provider, blocks, or other factors. When testing your proxy, you’ll see exactly at which stage the error occurs.

How we check your proxy

We make a request from our server to your proxy using the credentials you provided. Our algorithms perform step-by-step checks, analyzing the TCP connection in detail, followed by the HTTP/SOCKS connection. If an error occurs at any stage, we report it immediately.

Check steps:

1. DNS resolution – If you provided a domain (host), the first step is to resolve the IP address for connecting to the proxy. The DNS server may not have a corresponding domain-IP mapping, or the IP may differ. The DNS server might not respond in time. Even at this stage, the connection to the proxy can fail, even though the proxy itself is working.
2. Network route setup to the proxy by IP – Internet traffic passes through intermediate nodes (network equipment). One of these nodes may refuse the connection due to errors, overload, or malfunction.
3. TCP connection to the proxy – The proxy may not be working or may reject the connection due to overload or errors. The proxy might not accept connections using the protocol you specified.
4. TLS connection establishment – Issues may occur with the security certificate or due to mismatched connection credentials (incorrect login or password).

The result of the check will be the proxy status: Alive / Dead.
However, Alive only means that the proxy was reachable. Whether the proxy can connect to other sites is determined in the next stage of testing.

Proxy connectivity & latency

How your proxy works with websites

In this test, we make several connections through the proxy to popular websites and measure connection latency. We also check the proxy for any leaks of your original IP address.

How we check your proxy

At this stage, we connect through the proxy to several popular global websites. We analyze the connection step by step — both to the proxy and to the target sites — evaluate performance metrics, and provide you with detailed insights.

Sometimes a proxy is alive and working, but access to certain websites through it may still be unavailable. This can happen due to restrictions on the website’s side or the provider’s side — for example, geo-blocking (country restrictions). In some cases, the proxy quality is too low, and it gets blocked by websites.

Check stages:

1. Target Reachability – verifies whether the proxy can connect to target websites.
2. Anonymity Checking – determines whether your real IP address is exposed to the target site or only the proxy’s external IP is visible.
3. TTFB (Time to First Byte) – measures the time from the start of a request until the first byte is received from the website. This includes network latency, proxy processing time, and the server’s response speed.
4. Latency metrics:
   1. RTT (connect time via proxy) – the time required to establish a connection through the proxy (set up and prepare the channel to the target site). This reflects how quickly the connection starts, without accounting for page loading.
   2. RTT jitter (connection stability) – how much RTT varies across multiple attempts. Low jitter means a stable connection; high jitter indicates fluctuations in the network or routing.
   3. TTFB jitter (response stability) – how much TTFB varies between attempts. High jitter usually means responses arrive inconsistently (e.g., due to proxy overload, queuing, or unstable server response).
   4. Proxy processing (proxy-added delay) – an estimate of the delay introduced by the proxy itself, beyond normal network latency. We assess this as follows: if the connection is established quickly (normal RTT), but the first byte arrives significantly later (high latency), the proxy is likely overloaded or processing requests with delay

Important: Different types of proxies have different baseline latency expectations. Mobile proxies typically have the highest latency. From a usability perspective, this is a drawback — however, it increases the level of trust mobile IPs receive from anti-fraud and security systems of major websites.

Interpreting the Metrics

It is important to note that each type of proxy has its own "normal" metric values. Keep in mind that mobile proxies typically have much higher values. From a usability perspective, these higher values can make using the proxy slightly more challenging. However, website security systems also monitor these metrics, so higher metrics for mobile proxies can actually increase trust from websites.

Problem Signals:

• RTT significantly higher than ping → the proxy takes a long time to establish a connection (queueing, slow uplink, overload).
• RTT fluctuates heavily (high RTT jitter) → unstable network/radio channel (often mobile) or poor routing.
• RTT normal but TTFB high → usually a proxy-side issue (processing/queueing) or the website is “thinking.”
• Both RTT and TTFB high → usually due to geography, routing, or network type (especially mobile).
• Low RTT jitter but high TTFB jitter → the network is stable, but the “spikes” are caused by the proxy (queueing, rate limits, backend switching) or the website.

Anti-Fraud System Reactions:

• Too low RTT for a “mobile” IP → suspicious
• Too stable RTT → likely a server proxy
• Unnatural jitter → detected as a bot
• Too stable TTFB (latency) → likely a server
• Too low latency for a mobile ASN → suspicious

Description of response statuses and explanations

Learn about errors

Read the article “Error codes when checking proxies Proxy-checker OnlineProxy”.