© 2015, The Author(s). The η transition form factor is analyzed for the first time in both space- and time-like regions at low and intermediate energies in a model-independent approach through the use of rational approximants. The (Formula presented.) experimental data provided by the A2 Collaboration in the very low-energy region of the dielectron invariant mass distribution allows for the extraction of the most precise up-to-date slope and curvature parameters of the form factors as well as their values at zero and infinity. The impact of these new results on the mixing parameters of the (Formula presented.) system, together with the role played by renormalization dependent effects, and on the determination of the (Formula presented.) radiative decays is also discussed.