Sparse6 is a text-based file format for storing one or more undirected graphs.

The GraphTheory[ImportGraph] and GraphTheory[ExportGraph] commands can read from and write to this format.

The general-purpose commands Import and Export also support this format.

$\mathrm{Petersen}≔\mathrm{Import}\left(''example/petersen.s6''\,\mathrm{base}=\mathrm{datadir}\right)$

$\mathrm{Petersen}≔\mathrm{Graph\; 1:\; an\; undirected\; unweighted\; graph\; with\; 10\; vertices\; and\; 15\; edge(s)}$

$\mathrm{GraphTheory}:-\mathrm{DrawGraph}\left(\mathrm{Petersen}\,\mathrm{style}=\mathrm{spring}\right)$

McKay, B.D. and Piperno, A., Practical Graph Isomorphism, II, Journal of Symbolic Computation, 60 (2014), pp. 94-112, doi:10.1016/j.jsc.2013.09.003