The MLS Cup Playoffs have been a constant feature of the Major League Soccer season over the past 20 years, but that’s just about the only constant when it comes to the postseason.

There have been a few … OK, many format changes over the years. Let’s take a walk down memory lane and take a closer look at the shifts over time.

1996-99:

Qualification format: Eight teams (the top four from each conference) qualify for the playoffs.

Competitive format: The big innovation here was that the conference semifinals and conference finals were best-of-three series, with the higher seed hosting the first and third games, akin to baseball or basketball. Interestingly, in 1997, none of the best-of-three series went to a third game because all were two-game sweeps.

In keeping with the shootout era of MLS, playoff games could only end in a win or loss, decided via 35-yard shootouts if necessary.

MLS Cup, however, was a single, stand-alone game – the same as it’s been all 20 seasons.

2000-01:

Qualification format: With MLS divided into three divisions, the top eight teams across the league reached the postseason.

Competitive format: The quarterfinal and semifinal rounds remained best-of-three series, but with the shootout eliminated, draws could stand as a final result after a 10-minute, sudden-death overtime period, just as during the regular season. Teams needed five points to win a series, meaning a win and a tie in the first two games would still result in a Game 3. In the 2000 Kansas City Wizards-LA Galaxy semifinal series, the teams were even on results in the series (1-1-1) at the end of the third game, meaning an additional sudden-death period was played, which Kansas City won. In 2001, the Galaxy beat the MetroStars in a similar sudden-death tiebreaker in the quarterfinals.

2002:

Qualification format: Back to a two-conference alignment, eight teams qualified for the playoffs yet again, but it was the top eight teams by points, regardless of their conference. As a result, all five Western Conference teams qualified in 2002, while only three made it from the East.

Competitive format: The previous best-of-three series prevailed in the first two rounds again, with sudden-death extra time coming at the end of games and series when needed.

2003-06:

Qualification format: Eight teams made the playoffs, with the top four in each conference qualifying.

Competitive format: Out with the old, in with the new, as the best-of-three series was replaced by a two-leg format in the conference semifinals, with the aggregate score determining the winner and sudden-death extra time used to break aggregate ties in 2003. After that year, standard 30-minute extra time was implemented, with series or stand-alone games still going to penalty kicks if needed. The conference finals, along with MLS Cup, were winner-take-all matches.

2007-10:

Qualification format: Eight teams qualified, but with a modified format: The top two teams in each conference automatically qualified, with the four best teams remaining, regardless of conference, also clinching a berth.

In cases where one conference had more playoff teams than the other, teams were moved to the other conference bracket to make it even, producing three consecutive MLS Cup finals (2008-10) between teams from the same conference.

Competitive format: The format remained unchanged, with two-leg conference semifinals, a one-game conference final and a stand-alone MLS Cup final.

2011-14:

Qualification format: With the number of teams in the league expanding to 18 (and in subsequent years, more) by 2011, the playoff field was expanded as well, to 10 teams, the top five from each conference.

Competitive format: The bottom four teams played in two single-elimination games, with the winners going on to the two-leg conference semifinals to face a top seed. Conference finals remained stand-alone games in 2011 before becoming two-leg aggregate series in 2012. Away goals were introduced as a series tiebreaker for the first time in 2014 (and wound up deciding two of the six series).

Beginning with the 2012 season, MLS Cup was moved from a predetermined venue to the home field of the finalist with more regular-season points.

2015:

Qualification format: The field expands again this year, to 12 teams, with the top six teams in each conference reaching the postseason.

Competitive format: The format remains very similar to 2014, with the four lowest seeds in each conference playing in a single-game Knockout Round, now expanded to four total games. The winners from this round are re-seeded ahead of the conference semifinals. Conference semifinals and conference championships remain two-leg aggregate series, and MLS Cup remains a one-game affair at the home of the finalist with the most regular-season points.