The first-to-file rule is a doctrine of comity providing that “where substantially identical actions are proceeding in different courts, the court of the later-filed action should defer to the jurisdiction of the court of the first-filed action by either dismissing, staying, or transferring the later filed suit.” The two actions need not be identical—only substantially similar. The first-to-file rule is “not a rigid or inflexible rule to be mechanically applied,” but is a matter of sound judicial administration and its application is left to the discretion of the trial court. The purpose of the rule is to promote efficiency and to avoid duplicative litigation, and, thus, it should not be lightly disregarded.
A doctrine of comity “is a principle of courtesy by which the courts of one jurisdiction may give effect to the laws and judicial decisions of another jurisdiction out of deference and respect.” Comity is appropriately invoked according to the sound discretion of the trial court, and may even be raised sua sponte.
When applying the first-to-file rule, courts look to three threshold factors: “(1) the chronology of the two actions; (2) the similarity of the parties, and (3) the similarity of the issues.” “[T]he first-to-file rule does not require strict identity of the parties, but rather substantial similarity.” Likewise, the sameness requirement does not mandate that the two actions be identical; it is satisfied if they are sufficiently similar.
 SAES Getters S.P.A. v. Aeronex, Inc., 219 F.Supp.2d 1081, 1089 (S.D. Cal. 2002).
 Inherent.com v. Martindale–Hubbell, 420 F.Supp.2d 1093, 1097 (N.D. Cal. 2006).
 Pacesetter Sys., Inc. v. Medtronic, Inc., 678 F.2d 93, 94–95 (9th Cir. 1982) (explaining that declining jurisdiction based on the first-to-file rule is discretionary, not mandatory, with the trial court).
 Alltrade, Inc. v. Uniweld Prod., Inc., 946 F.2d 622, 625 (9th Cir. 1991).
 Gonzales–Alpizar v. Griffith, 130 Nev. Adv. Op. 2, 317 P.3d 820, 826 (2014) (internal quotation omitted).
 Mianecki v. Second Judicial Dist. Court, 99 Nev. 93, 97–98, 658 P.2d 422, 424–25 (1983).
 See Stone v. City & County of San Francisco, 968 F.2d 850, 855 (9th Cir. 1992).
 Global Experience Specialists, Inc. v. Cunniffe, 2:14–cv–00421–JCM–NJK, 2014 WL 3748931, at *4 (D. Nev. July 30, 2014) (quoting Nesbit v. Fornaro, 2011 WL 1869917, at *2 (D. Nev. Mar. 31, 2011)).
 Id. (quoting Nesbit, 2011 WL 1869917, at *3).