In this paper, cosmic distance duality relation (CDDR) is probed without considering any background cosmological model. The only a priori assumption is that the Universe is described by the Friedmann–Lemaître–Robertson–Walker (FLRW) metric. The strong gravitational lensing data is used to construct the dimensionless co-moving distance function d(z) and latest type Ia supernovae Pantheon+ data is used to estimate luminosity distances at the corresponding redshifts z. Using the distance sum rule along null geodesics of the FLRW metric, the CDDR violation is probed in both flat and non-flat spacetime by considering two parametrizations for η(z), the function generally used to probe the possible deviations from CDDR. The results show that CDDR is compatible with the observations at a very high level of confidence for linear parametrization in a flat Universe. In a non-flat Universe too, CDDR is valid within the 1σ confidence interval with a mild dependence of η on the curvature density parameter ΩK. The results for nonlinear parametrization also show no significant deviation from CDDR.

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