Example of a colour-magnitude diagram obtained for the NB filter J0410 on a DR1 pointing (out of 511). Our photometric cuts are summarised as follows: the blue dashed-dotted line shows the Δm^NB-significance threshold, while the vertical red line marks the NB S/N limit. We exclude sources below the blue dashed-dotted line and inside the grey shaded area. The orange horizontal dotted line shows Δm^NB associated to EW = 50 Å (see Eq. (7)). Grey-blue dots mark all the J-PLUS detections in the pointing, while red and purple crosses show z​ ∼ ​2.4 QSOs and low-z galaxies from SDSS DR14. Yellow triangles show J-PLUS mock data of z​ ∼ ​2.4 SF LAEs (Izquierdo-Villalba et al. 2019). Finally, our Lyα-emitting candidates are shown as green dots.