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Molecular hydrogen (H 2 ) absorption features observed in the line of sight to Q2348−011 at redshift  z  abs ≃ 2.426 are analysed for the purpose of detecting a possible variation of the proton‐to‐electron mass ratio μ≡ m  p / m  e . By its structure, Q2348−011 is the most complex analysed H 2  absorption system at high redshift so far, featuring at least seven distinctly visible molecular velocity components. The multiple velocity components associated with each transition of H 2  were modelled simultaneously by means of a comprehensive fitting method. The fiducial model resulted in Δμ/μ= (−0.68 ± 2.78) × 10 −5 , showing no sign that μ in this particular absorber is different from its current laboratory value. Although not as tight a constraint as other absorbers have recently provided, this result is consistent with the results from all previously analysed H 2 ‐bearing sightlines. Combining all such measurements yields a constraint of |Δμ/μ|≤ 10 −5  for the redshift range  z = 2–3.

Constraint on a variation of the proton‐to‐electron mass ratio from H 2 absorption towards quasar Q2348−011