A sorting system for sorting articles, comprising a lower sorter including a plurality of lower sorter units for supporting articles, which lower sorter units are drivable along a loop-shaped lower path in a lower transport direction, an upper sorter including a plurality of upper sorter units for supporting articles, which upper sorter units are drivable along a loop-shaped upper path in an upper transport direction, wherein the upper path extends above the lower path, wherein the lower sorter is provided with a first lower input and a second lower input where articles are supplied to the lower sorter units under operating conditions, wherein the first and second lower inputs (6, 7) are located at a distance from each other along the lower path, a first lower output and a second lower output where articles are selectively removable from the lower sorter units, the first lower output being located downstream of the first lower input and upstream of the second lower input, the second lower output being located downstream of the second lower input and upstream of the first lower input, wherein the upper sorter is provided with a first upper input and a second upper input where articles are supplied to the upper sorter units under operating conditions, wherein the first and second upper inputs (11, 12) are located at a distance from each other along the upper path, a first upper output and a second upper output where articles are selectively removable from the upper sorter units, the first upper output being located downstream of the first upper input and upstream of the second upper input, the second upper output being located downstream of the second upper input and upstream of the first upper input, a pre-sorter being configured to supply articles to the lower and upper sorter units (4, 5) at the second lower and upper inputs (7, 12), which pre-sorted articles are destined for the second lower and upper outputs (9, 14), respectively, substantially only, wherein the second lower output is located at the first upper output and the first lower output is located at the second upper output. a lower sorter including a plurality of lower sorter units for supporting articles, which lower sorter units are drivable along a loop-shaped lower path in a lower transport direction, an upper sorter including a plurality of upper sorter units for supporting articles, which upper sorter units are drivable along a loop-shaped upper path in an upper transport direction, wherein the upper path extends above the lower path, wherein the lower sorter is provided with a first lower input and a second lower input where articles are supplied to the lower sorter units under operating conditions, wherein the first and second lower inputs (6, 7) are located at a distance from each other along the lower path, a first lower output and a second lower output where articles are selectively removable from the lower sorter units, the first lower output being located downstream of the first lower input and upstream of the second lower input, the second lower output being located downstream of the second lower input and upstream of the first lower input, wherein the upper sorter is provided with a first upper input and a second upper input where articles are supplied to the upper sorter units under operating conditions, wherein the first and second upper inputs (11, 12) are located at a distance from each other along the upper path, a first upper output and a second upper output where articles are selectively removable from the upper sorter units, the first upper output being located downstream of the first upper input and upstream of the second upper input, the second upper output being located downstream of the second upper input and upstream of the first upper input, a pre-sorter being configured to supply articles to the lower and upper sorter units (4, 5) at the second lower and upper inputs (7, 12), which pre-sorted articles are destined for the second lower and upper outputs (9, 14), respectively, substantially only, wherein the second lower output is located at the first upper output and the first lower output is located at the second upper output.