This Fidabio poster demonstrates how in-solution binding kinetics can be measured without surface immobilization, avoiding the surface-chemistry optimisation and regeneration challenges of biolayer interferometry (BLI) and surface plasmon resonance (SPR). Flow Induced Dispersion Analysis (FIDA) was used to determine association and dissociation rate constants (kon and koff), equilibrium dissociation constants (KD) and hydrodynamic radius for protein–protein and protein–small-molecule interactions, with results in good agreement with SPR. It is an example of using FIDA to characterise binding affinity and kinetics directly in solution.