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tokens: need of high angular resolution observations to robustly discriminate different flavours of magnetically regulated collapse models, since an hourglass at large scales can arise from different initial conditions, and outcomes of the protostellar accretion process. The B335 case could be more similar to the L1157 one if L1157 would be observed at similar physical scales (50 au), although our B335 ALMA map does not show a clear complete hourglass morphology at the envelope scale as the one observed in L1157. This is due to a combination of distance (L1157 is 2–3 times farther than B335), and filtering of the extended emission from the lower column density outer envelope, in our ALMA observations. L1527 in Taurus is another case of protostar seen almost perfectly edge-on, although it is probably more evolved than B335 (Chen et al. 1995 ; Ohashi et al. 1996 ). In L1527, the 1.3 mm polarized continuum at scales of 500–1000 au shows a magnetic field mostly aligned along the equatorial plane (Hull et al. 2014 ; Segura-Cox et al. 2015 ), while at larger scales it is roughly aligned with cavity walls (Davidson et al. 2014 ). This source has a larger disc radius, ≃60 au, and rotation is detected (Ohashi et al. 2014 ). Segura-Cox et al. ( 2015 ) use this example to suggest the topology of the B-field lines could be a method to help identify candidate Class 0 disc sources with R > 10 au because a transition from poloidal to radial field in the equatorial plane should be detected only in the sources where large rotational energy led to the formation of large discs: our observations of an equatorial component in B335, which harbours no disc at R > 10 au, challenge this simple view, and we suggest both strong pinching and strong coiling of the field lines can produce such a pattern. We also stress that inclination effects (B335 is an isolated edge-on source) and a simple environment might (i) help to enhance the detection of the strongly pinched magnetic field in the equatorial plane, and (ii) identify whether the magnetic field is regulating the evolution of the collapsing matter. For example, in more dynamic and/or clustered environments, polarization studies do not always reveal hourglass shapes, nor well-organized fields (Zhang et al. 2014 ). Among the few other cases where the magnetic field has been resolved well enough, the Serpens protostar SMM1 observed with ALMA (Hull et al. 2017 ) shows a complex magnetic field morphology, although mostly aligned with the outflow's cavity. 5 CONCLUSIONS Our ALMA 233 GHz polarized dust emission map shows a well-organized pattern at scales 50–500 au, mostly distributed along two structures: the pronounced east–west outflow cavity walls where the field is aligned with the outflow direction and reminiscent of the large-scale east–west native field, and the high-density equatorial plane where the field line segments appear to be mostly aligned with the equatorial plane. Because observations suggest there is only room for