There are some slight differences in the rules used in different countries around the world, however for almost all practical purposes (more than 99.999% of games) they produce the same result.
For a comparison between the various rules sets see our description of various rulesets [1] or a more technical rules comparison [2].
For our BGA Rules, we have adopted rules based on the American Go Association (AGA) rules. We use these in tournaments (with the exception of Pair Go [3]), as opposed to Japanese rules used previously. Club players may use BGA rules or the Japanese rules, or whatever they are comfortable with.
Please see our AGA rules [4] section and the policy page on the BGA Rules of Go [5] for the full details.
We also have a single page Quick Ref [6] produced for the UK Go Challenge which use BGA Rules. We also have some FridgeGo rules [7] that were written for inclusion in the FridgePlay 9x9 magnetic set.
Some other sites which also present the rules of Go in English, not in a formal way, include:
Which of these you like is primarily a stylistic issue.
Ko is the main repeating position for which there is a specific rule to avoid the game going on forever. However, there are more complicated, and usually fairly rare positions which are repeating and for which special rules are needed to find a conclusion for a game in some rule sets. We have here some of these repeating positions [12]. The rules related to these differ between the major rule sets [2]; under BGA Rules the rule about board repetitions solves most of these.
Pair Go [3] has special rules and etiquette [13] to cater for two players playing as a team.
For links to rule sites in foreign languages see our collection of Foreign Links [14].
The Rules of General Graph Go [15] are how a mathematician may see Go.
We have an analysis of this question [16].
We ran a Sunjang Baduk Tournament [17] in 2007.
Links:
[1] http://message.britgo.org/general/itd/7
[2] http://message.britgo.org/rules/compare
[3] http://message.britgo.org/pairgo
[4] http://message.britgo.org/rules/aga
[5] http://message.britgo.org/policy/policies6-9
[6] http://www.ukgochallenge.com/quickref.html
[7] http://message.britgo.org/rules/fridgego
[8] http://gobase.org/studying/rules/?id=0&ln=uk
[9] http://www.telgo.com/
[10] http://senseis.xmp.net/?BasicRulesOfGo
[11] http://playgo.to/iwtg/en
[12] http://message.britgo.org/rules/molasses
[13] http://message.britgo.org/pairgo/pairrules
[14] http://message.britgo.org/links/foreign
[15] http://message.britgo.org/rules/graphgo
[16] http://message.britgo.org/rules/maxgroup
[17] http://message.britgo.org/tournaments/sunjang