A method of applying a sealing strip of heat seal material onto a web of packaging material within a strip application apparatus comprising: - a conveying phase during which the web of packaging material is advanced along a web advancement path; - an application phase during which a first longitudinal portion of the sealing strip is applied onto a longitudinal edge of the web of packaging material advancing, in use, along the web advancement path; - a sealing phase during which the first longitudinal portion of the sealing strip is sealed onto the longitudinal edge; - a control phase during which at least a correct alignment or a misalignment of the sealing strip with respect to the web of packaging material is detected and/or determined; characterized in that the control phase comprises at least the following sub-phases: - an imaging sub-phase during which an image of at least a second longitudinal portion of the sealing strip projecting laterally from the longitudinal edge and at least one reference marker of the strip application apparatus is acquired; - a determination sub-phase during which the acquired image is analyzed to determine at least a first transversal distance between the reference marker and a longitudinal border of the second longitudinal portion opposite to the longitudinal edge of the web of packaging material; and - an analysis sub-phase during which the correct alignment or the misalignment is evaluated as a function of at least the first transversal distance determined during the determination sub-phase; wherein during the imaging sub-phase the at least one image is acquired to also contain the longitudinal edge of the web of packaging material; wherein during the determination sub-phase also a second transversal distance between the longitudinal edge and the reference marker is determined; and wherein during the analysis sub-phase at least the correct alignment or the misalignment of the sealing strip is evaluated as a function of the first transversal distance and the second transversal distance. - a conveying phase during which the web of packaging material is advanced along a web advancement path; - an application phase during which a first longitudinal portion of the sealing strip is applied onto a longitudinal edge of the web of packaging material advancing, in use, along the web advancement path; - a sealing phase during which the first longitudinal portion of the sealing strip is sealed onto the longitudinal edge; - a control phase during which at least a correct alignment or a misalignment of the sealing strip with respect to the web of packaging material is detected and/or determined; - an imaging sub-phase during which an image of at least a second longitudinal portion of the sealing strip projecting laterally from the longitudinal edge and at least one reference marker of the strip application apparatus is acquired; - a determination sub-phase during which the acquired image is analyzed to determine at least a first transversal distance between the reference marker and a longitudinal border of the second longitudinal portion opposite to the longitudinal edge of the web of packaging material; and - an analysis sub-phase during which the correct alignment or the misalignment is evaluated as a function of at least the first transversal distance determined during the determination sub-phase;