The Vienna RNA secondary structure server offers a web interface to the Vienna RNA software package, providing three main services: predicting secondary structure from a single sequence, predicting the consensus secondary structure for a set of aligned sequences, and designing sequences that will fold into a predefined structure. The server includes CGI scripts equivalent to the command-line programs RNAfold, RNAaliifold, and RNAinverse. The RNAfold server predicts the minimum free energy (mfe) structure and equilibrium base pairing probabilities, while the Alifold server predicts the consensus structure for aligned sequences. The inverse fold server designs sequences to fold into a specified structure. The server supports various visualization formats, including PostScript and SVG, and aims to improve user experience and interoperability with other programs. Future plans include enhancing visualization and offering standardized data exchange formats.The Vienna RNA secondary structure server offers a web interface to the Vienna RNA software package, providing three main services: predicting secondary structure from a single sequence, predicting the consensus secondary structure for a set of aligned sequences, and designing sequences that will fold into a predefined structure. The server includes CGI scripts equivalent to the command-line programs RNAfold, RNAaliifold, and RNAinverse. The RNAfold server predicts the minimum free energy (mfe) structure and equilibrium base pairing probabilities, while the Alifold server predicts the consensus structure for aligned sequences. The inverse fold server designs sequences to fold into a specified structure. The server supports various visualization formats, including PostScript and SVG, and aims to improve user experience and interoperability with other programs. Future plans include enhancing visualization and offering standardized data exchange formats.