For the 2020 season, the league is played in two rounds (home-and-away), each team playing a total of 34 matches.
Each team must have at least 3 players holding professional contracts. Also for this season, 5 foreign players are allowed per team, plus 1 more from the ASEAN partner country of J.League or from other AFC countries. The matchday roster will consist of 18 players, and up to 3 substitutes will be allowed in a game. The three under-23 clubs can have up to three overage players and one of them must be a goalkeeper.
Rules for promotion to J2 are largely similar to those of Japan Football League in recent seasons: to be promoted, a club must hold or be granted a J2 license and finish in top 2 of the league. Since 2017, the champions and the runners-up have been promoted directly and replace the 21st- and 22nd-placed J2 clubs. If only the champion or runner-up holds or is given a J2 license, only the bottom club of J2 is relegated; if both top 2 finishers are ineligible for promotion, then no teams will be promoted to or relegated from J2. For promotion purposes, under-23 teams are excluded from the final table when considering which teams are eligible for promotion. An extreme example would be the following scenario: If all three under-23 teams finished in the top 3, then the fourth- and fifth-placed teams would be eligible for promotion (subject to the license requirement).
No relegation to JFL is planned in the foreseeable future.