Although the sources seem speak a clear language about substitutions in football, there are many fiction, many myths about the development.
I know of exceptions in some countries on the European mainland between the First and Second World Wars. The four British associations also knew about this and tried to press FIFA to comply with the rules first. But in the end (1931) they unofficially let the continental European way continue. It had already become a common law there in the few years it had been in existence, and it was much appreciated.
In this post I give an overview of the development of substitutions in football in a nutshell.
Here is the dr;tl version most important data of substitutions in football[dr;tl = don’t read; too long]
There were no substitutions in the modern sense, but by mutual agreement, the possibility of replacing players who appeared too late with another.
Substitutions are only possible in non-competition matches and in the event of a serious injury, and only after prior agreement between the two teams. The referee must also be informed of the agreement, as must the substitution during the match.
In continental Europe, it has become a sort of common law in some countries to allow substitutions beyond the 1923 regulation. The four British associations unofficially tolerate FIFA’s casual attitude.
There are experiments with substitutions of injured players at competitive matches. The experiments took place at a FIFA international youth tournament, the 1953 World Cup qualifiers and the 1954 World Cup.
The IFAB allows national associations to allow substitutions of injured players at competitive matches.
In England, up to two players per team can be substituted per match regardless of injury. From the 1966/67 season also in Scotland.
The IFAB granted the national associations to allow the substitution of up to two players per team per match, regardless of injury.
Introduction of the 2+1 rule: two field players and a goalkeeper may be substituted.
Up to three replacements, independent of position, are allowed.
The national associations may allow return substitution in recreational and amateur football.
After two years as a global experiment, the fourth substitution during extra time is officially introduced.
Until the end of December 2022, national associations may allow up to five substitutions from late spring, i.e. the restart after the Covid 19 season interruption. These must be made in a maximum of three interruptions of the game (excluding the half-time break).