Protein structure alignment — compare two structures by residue-level superposition. Provide PDB text (upload or paste) or a UniProt accession, which is fetched from the AlphaFold DB and cached on this server. Matching is a global sequence alignment (Needleman–Wunsch) followed by iterative Kabsch superposition; RMSD, TM-score and per-residue deviations are computed locally.