How hockey's rules changed.

Before the NHL

The earliest games looked very different. The 1875 Montreal game was nine a side, and at the 1886 Kingston game there were no lines on the ice and goalies were not allowed to lie down, according to Queen's University's encyclopedia. Wikipedia, citing the SIHR researchers Gidén, Houda and Martel, says teams went from nine to seven a side around 1880.

The National Hockey Association made two changes the NHL kept. Scouting the Refs dates the move from two 30-minute halves to three 20-minute periods to 1910-11, and the move from seven players a side to six, by dropping the rover, to 1911-12; Wikipedia dates the six-man game to 1911.

The early NHL: opening up the game

Unless another source is named, the seasons below come from Scouting the Refs.

The forward pass

Forward passing came in stages. Scouting the Refs says the 1918-19 lines allowed forward passes only in the defensive zone; a search summary of another source says the neutral zone, so what was first permitted is disputed. Time magazine reported in 1929, as read through a search summary, that the NHL had ruled the forward pass, until then barred except in a team's own territory, would be allowed in all zones. The Hockey News says scoring more than doubled after the 1929-30 change and that Boston became the first team to score 100 goals in a season.

Icing and the red line

The Hockey News explains icing as a rule that stopped defending teams simply firing the puck the length of the ice. It describes the centre red line of 1943-44 as allowing passes out of the defensive zone up to centre, and says the NHL regards it as the start of its modern era. The Hockey News also dates standardised periods with stop-time, a change of ends after each period and sudden-death overtime to 1927, and links the 1956-57 power-play rule to the scoring power of the Montreal Canadiens.

Overtime and officiating, 1983 to 2004

• 1983-84: five-minute sudden-death overtime returns for regular-season ties (Scouting the Refs). Wikipedia notes the World Hockey Association had used regular-season sudden-death overtime before the NHL.
• 1988-89: delayed, or tag-up, offside introduced. It was dropped in 1996-97 and brought back in 2005-06 (Scouting the Refs).
• 1991-92: video replay adopted for goal and no-goal decisions (Scouting the Refs; The Hockey News says 1991).
• 1992-93: a game misconduct for instigating a fight added, along with minor penalties for diving (Scouting the Refs).
• 1998-99: the two-referee system phased in. Scouting the Refs says each team played 20 games with a four-official crew that season and 50 the next, and that it became standard for every game in 2000-01.
• 1999-2000: regular-season overtime becomes four-on-four (Scouting the Refs).

The 2005-06 changes

The 2004-05 season was lost to a lockout, and the league returned with a package of changes. The NHL's own announcement from 2005 was not found; this summary rests on Scouting the Refs and Wikipedia.

• A shootout for regular-season games still tied after five minutes of overtime. Wikipedia says it used three shooters per team and then sudden death, and applied only in the regular season.
• The centre red line removed for passing, so two-line passes became legal.
• Tag-up offside restored.
• Goaltenders limited to playing the puck behind the net inside a trapezoid.
• A team that ices the puck may not change lines, according to Wikipedia.

Several of these still stand. The NHL Official Rules 2026-2027 define the trapezoid as the goalkeeper's restricted area (Rule 1.8), and Rule 84.4 sets out a shootout of three shots per team, then sudden death, in the regular season only. Internationally, Wikipedia's World Championships article says the IIHF used shootouts to decide tied medal-round games from 1992.

Since 2010

• 2010-11: a major penalty for an illegal check to the head (Scouting the Refs).
• 2013-14: hybrid icing. CBS Sports reported in September 2013 that players approved it after a preseason trial, so that linesmen judge the race for the puck at the faceoff dots instead of letting players race into the end boards. The NHL Official Rules 2026-2027 (Rule 81.1) still have the linesperson decide by the time the first player reaches the end-zone faceoff dots.
• 2015-16: three-on-three overtime and the coach's challenge. The Globe and Mail reported that the Board of Governors approved both in June 2015: three-on-three to reduce the number of games decided by shootouts, and a challenge limited to goals that may have involved offside or goaltender interference. Overtime at three skaters a side is in the 2026-27 rulebook (Rule 84.1), and the coach's challenge is Rule 38.
• 2026-27: new players must wear neck protection (Rule 9.8). See equipment history.

Body checking in youth and women's hockey

Amateur bodies have moved the age at which body checking is allowed. The United States of Hockey blog reported in June 2011 that USA Hockey's board voted, with 88 percent approval, to ban body checking at Pee Wee (ages 11 and 12) from 2011-12 and allow it from Bantam up. In Canada, the Chatham-Kent Sports Network reported that Hockey Canada's board voted at its May 2013 annual meeting to remove body checking from Peewee and below from 2013-14, deferring it to Bantam, and the Ontario Minor Hockey Association described it as a new national standard. Current ages under each body's rulebook are on the body-checking rules page.

In women's hockey, Wikipedia says full body checking was allowed at the first Women's World Championship in 1990 and that the IIHF ruled it out of women's hockey afterwards; the year the ban took effect was not found. One search result, whose source could not be identified, claimed instead that checking was not allowed at the 1990 event under local rules.