Posterior distributions for τ for various datasets. Solid lines represent τ constraints ignoring TE, dashed lines assume full TEB likelihood. Only τ and ln(10¹⁰A_s) are sampled, whereas the remaining ΛCDM parameters are fixed to common fiducial values. The green and yellow lines show results obtained with the official Planck Legacy low-ℓ likelihoods (Planck Collaboration V 2020). The red line is obtained running the SRoll2 likelihood (Pagano et al. 2020). The blue lines represent the results of this paper.