A method of applying a sealing strip onto a web of packaging material comprising advancing the web along a web advancement path; applying a first longitudinal portion of the sealing strip onto a longitudinal edge of the web, sealing the first longitudinal portion of the sealing strip onto the longitudinal edge, detecting and/or determining a correct alignment of the sealing strip with respect to the web. The detecting and/or determining of the correct alignment comprises acquiring an image of a second longitudinal portion of the sealing strip and a reference marker of a strip application apparatus, analyzing the acquired image to determine at least a first transversal distance between the reference marker and a longitudinal border of the second longitudinal portion; and evaluating the correct alignment/misalignment as a function of at least the first transversal distance.