Concorde supports several file formats. Some describe a graph's nodes and edges while others contain only nodes. If a file contains nodes it provides their x and y coordinates as well. Edges are described by the nodes that they connect. Concorde does not allow for multiedges. All edges are undirected.
The following table lists the supported formats, the file extensions used by them, whether they contain node and edge definitions, and which commands may read from or save to these files.
| Format | Extension | Nodes | Edges | Commands | |||
| DIMACS | .geom | Yes | No | Open | |||
| QS | .qs | Yes | Yes | Open, Save, Save As | |||
| TSPLIB | .tsp | Yes | No | Open, Save, Save As |
The DIMACS format is used in the Discrete Mathematics and Theoretical
Science Center's Algorithm Implementation Challenge, see
DIMACS Challenges . Concorde supports two DIMACS's geom format which
defines a set of nodes and their coordinates.
The TSPLIB format is used in a library of TSP instances maintained at the University of Heidelberg. Concorde interpretes only those TSPLIB files that define sets of nodes in two dimensional space.