Countries will split into two conferences - a European conference and a Rest of the World conference - with three divisions within those conferences.
Initially the Six Nations teams would make up the European conference while the current Rugby Championship nations would be joined by two tier two nations to expand the competition to six teams based on world rankings - under the current rankings that would mean Fiji and Japan.
Both conferences will have a second six-team division and a third consisting of 16 teams, with countries able to move between divisions via promotion-relegation playoffs.
Each team plays each other once with the top two teams in each conference playing off in cross-conference semi-finals and grand final in November, giving the winner a maximum of 13 Tests in a calendar year.
Teams in the second division would follow the same format, finishing with promotion-relegation play-offs, while the third division will be split into four pools culminating in conference finals before the promotion playoffs.
The announcement comes after a week of intense speculation and controversy surrounding the competition, particularly around whether Pacific Island countries would be locked out of involvement for the proposed tournament, a discussion that led to some leading Pacific players threatening a potential World Cup boycott.
In a statement released overnight, though World Rugby admitted that some countries were against promotion-relegation, it was committed to ensuring every country had a pathway to the top.
"With the proposed model incorporating competitions that are not owned or run by World Rugby, not all unions are presently in favour of immediate promotion and relegation," the World Rugby statement said. "We continue to consider the feedback, but remain absolutely committed to an eventual pathway for all."
"Change is always difficult, and nobody expected complex multi-stakeholder discussions to be simple, however for a sport to grow and thrive, it must explore ways to innovate and evolve," it added.
"Player welfare is fundamental to our sport," it added. "Within the original proposal, players would play a maximum of 13 matches if their team reaches the final, compared to an average of between 12 and 14 Test matches presently. Most teams would play 11 matches."
The competition would run in its full format in two out of the four years in every World Cup cycle and without promotion-relegation in years where a British and Irish Lions tour takes place.
World Rugby also confirmed a possible expansion of the Rugby World Cup in 2027, a move to ensure the international tournament remains as the peak of the game.
One of the organisations that was particularly vocal in its opposition to the plan last week was the International Players Council (IRP), concerned about the workload on players, with
All Blacks captain and number eight Kieran Read and Ireland fly-half Johnny Sexton among those most critical.
The IRP released a statement overnight, saying it would meet to discuss the announced plans as well as a discussion with World Rugby about the relationship between the two bodies.
"Our players are incredibly passionate about having their voices heard, not just in relation to the proposed international season, but in respect of all player issues that impact the men's, women's, 15s and 7s game," IRP CEO Omar Hassanein said in a statement.
"We have an agreement with World Rugby which requires meaningful engagement on key player welfare issues, however, too often information fails to be provided in a manner that allows players to realistically influence the outcome.
"For the benefit of our game and to ensure we avoid situations where players feel they have to take a public stand, the relationship with World Rugby and the basis upon which we interact on key issues needs to be a lot more meaningful and effective.
"This will be central to our discussions when we meet as a team next week."