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Connection setup timing split by SYN, ACK and first byte.
The TCP Handshake tool measures the time breakdown of a full TCP connection setup — SYN, SYN-ACK and ACK — plus the time to first byte, so you can isolate where connection latency is introduced.
Enter a host and port (for example example.org:443) and run the tool. The probe opens a TCP connection and records the timing of each handshake phase.
Input: Host and port — e.g. example.org:443.
The output shows the duration of the SYN send, the SYN-ACK wait (server processing), the final ACK, and the time to first byte of data. A long SYN-ACK wait points to server-side accept latency; a fast handshake but slow first byte points to application-layer processing delay.
→ Separate network latency from application latency for a slow API.
→ Measure TTFB of an origin server behind a CDN.
→ Diagnose connection-accept bottlenecks on a busy service.
→ Compare IPv4 vs IPv6 connection setup time.
TTFB is the time from the moment the TCP connection is established until the first byte of the response body arrives. It captures server-side and application processing time separately from network round-trips, making it a key origin-performance metric.
The network path and TCP setup are healthy, but the application behind the port is slow to produce a response. Look at backend processing, database queries, or cold caches rather than the network.
A long SYN-ACK wait usually means the server’s accept queue (backlog) is full or the listening process is overloaded and slow to accept new connections. It can also indicate deep packet inspection or a proxy adding delay.