Redshift evolution of the best-fit star-forming, rest-optical size–mass relation parameters. Left panel: Size evolution for galaxies at a fixed stellar mass of M_* = 5 × 10¹⁰ M_⊙ in the range 0.35 ≤ z < 9. Centre panel: Evolution of the slope, α. Right panel: evolution in the intrinsic scatter, σ_logREFF. The diamonds and solid pink lines show the measurements and parametrised evolution from this paper. The HST-based measurements (Nedkova et al. 2021; Mowla et al. 2019; George et al. 2024; van der Wel et al. 2012) are shown in grey. The JWST-based studies from Ward et al. (2024) and Matharu et al. (2024) are shown in tan. The JWST-based work based on UV-bright ground-based selected star-forming galaxies from Varadaraj et al. (2024) are shown as grey squares. The HST-based parametrised fits to the redshift evolution from Mowla et al. (2019) and van der Wel et al. (2012) as well as the JWST-based size-evolution from Ward et al. (2024) are also included (see Table A.1 for values).