The leptonic and inclusive hadronic decay branching fractions of the
W
boson are measured using proton-proton collision data collected at
√
s
=
13
 
 
TeV
by the CMS experiment at the CERN LHC, corresponding to an integrated luminosity of
35.9
 
 
fb
−
1
. Events characterized by the production of one or two
W
bosons are selected and categorized based on the multiplicity and flavor of reconstructed leptons, the number of jets, and the number of jets identified as originating from the hadronization of
b
quarks. A binned maximum likelihood estimate of the
W
boson branching fractions is performed simultaneously in each event category. The measured branching fractions of the
W
boson decaying into electron, muon, and tau lepton final states are
(
10.83
±
0.10
)
%
,
(
10.94
±
0.08
)
%
, and
(
10.77
±
0.21
)
%
, respectively, consistent with lepton flavor universality for the weak interaction. The average leptonic and inclusive hadronic decay branching fractions are estimated to be
(
10.89
±
0.08
)
%
and
(
67.32
±
0.23
)
%
, respectively. Based on the hadronic branching fraction, three standard model quantities are subsequently derived: the sum of squared elements in the first two rows of the Cabibbo–Kobayashi–Maskawa (CKM) matrix
∑
i
j
|
V
i
j
|
2
=
1.984
±
0.021
, the CKM element
|
V
c
s
|
=
0.967
±
0.011
, and the strong coupling constant at the
W
boson mass scale,
α
S
(
m
2
W
)
=
0.095
±
0.033
.