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TCP Flags Decoder/Encoder
Decode and encode TCP control bits—SYN, ACK, FIN, RST, PSH, URG, ECE, CWR—with hex, decimal, and binary representations.
This tool handles input and primary processing in your browser and is designed not to send the input to QuickKit’s server.
How it works
Decode: enter a TCP flags value as hex (0x12), decimal (18), binary (0b00010010), or a comma/space-separated flag list (SYN,ACK or SYN ACK). Encode: toggle each of the 8 control bits (CWR, ECE, URG, ACK, PSH, RST, SYN, FIN) to compute the resulting value. Common combinations like SYN+ACK (connection accepted) and RST (reset) are noted. RFC 8311 / RFC 9293 defined the AE (Accurate ECN) bit above CWR for advanced congestion control, but this tool focuses on the classic 8 bits.