Replacement, reduction, and refinement of animal use in research are the cornerstone principles of laboratory animal welfare, with progress accelerating through new technologies.
The Three Rs have driven significant improvements in laboratory animal welfare over six decades, but full application remains inconsistent. Replacement technologies including organ-on-chip, human organoids, and AI modelling are increasingly powerful alternatives for many research questions. Reduction is hampered by lack of data sharing and replicate publication of similar studies. Refinement gains including environmental enrichment, social housing, and pain management protocols have improved daily welfare substantially. Regulatory push for Three Rs implementation has been important but voluntary measures have driven the most innovation.