Freestyle Chess vs Chess960: the same game under two names
Freestyle Chess and Chess960 are the same game. Same 960 starting arrangements, same pieces, same castling rule, same everything after move one. What differs is the label, who prints it, and the conventions of the events that use it.
Is Freestyle Chess the same as Chess960?
Yes, and the sameness is total rather than approximate. Both names describe chess played from a shuffled back rank, one of 960 legal orders, with the bishops on opposite colours, the king between the rooks, and Black mirroring White file for file. Both use the same castling rule, where the king finishes on g1 or c1 and the rook on f1 or d1 whatever squares the two started on. Both count the same 960 positions and in practice number them the same way, so a position anyone calls Freestyle 199 is position 199 in any Chess960 generator.
There is no Freestyle-only rule. There is no Chess960 rule that Freestyle drops. A game recorded in one can be replayed in the other with no conversion at all.
QNBRKNRBQNBRKNRBWhat actually differs?
Three things, none of them on the board.
The name itself, and who uses it. Chess sites, engines, opening databases and books say Chess960 almost without exception. FIDE says Fischer Random and awards a world title under that name. Freestyle Chess is the name attached to a circuit of elite invitational events, and because those events get general chess coverage rather than variant coverage, it is the name most likely to reach somebody who has never played the game.
Event conventions, which belong to tournaments and not to the variant. Any event played from shuffled positions has to settle a few questions its regulations then answer: how the position is drawn, how long before the round the players see it, whether they may prepare on it and for how long, the time control, and whether the same position is played twice with colours reversed so neither player owns the White side of a lopsided array. Organisers answer those differently and are free to change their answers between editions. None of it changes what is legal, and none of it is worth memorising from an article. Read the regulations of the event you care about.
Prominence. The competitive picture around the format moves: who plays, which events run, what the calendar looks like, who holds what. Those change often enough that any name or figure printed here would be wrong before long, so none is. The tour's own site is where that lives. Magnus Carlsen is the best-known public advocate of playing from shuffled positions, and coverage of him carries the name along.
Freestyle Chess vs classical chess
This is the comparison with something in it. Two differences, and both are narrow.
The first is the array: eight back-rank pieces shuffled instead of set in one fixed order. The second is the wording of the castling rule, which changes because the starting squares change while the destinations do not. Nothing else moves. All sixteen pawns start where they always start, so every pawn structure you have studied is still reachable and everything you know about it still holds.
What that costs and what it buys is a longer argument with its own page. The short version: preparation stops counting. A good deal of classical chess above club level is a contest of home analysis, which is a real skill honestly acquired, and shuffling the back rank sets its value at zero. Whether that is a gain depends on which of your skills you would rather have measured. Both sides are set out in Chess960 against standard chess.
One thing worth stating plainly. Standard chess is one of the 960. Under the usual numbering it is position 518, drawn with probability one in 960 like any other. Freestyle Chess is therefore not an alternative to chess. It is chess with the starting array chosen at random instead of by tradition, and roughly once in 960 games tradition wins the draw anyway.
Chess960, Fischer Random, Freestyle Chess, FRC
Four labels, one game, and the mess is worth untangling once.
Fischer Random is Bobby Fischer's name for it, announced in 1996. FRC abbreviates Fischer Random Chess and turns up in tournament regulations and engine documentation. Chess960 counts the legal arrangements, and it is the name in near-universal use on chess sites, in software and in books. Freestyle Chess is the event brand.
Two more you may meet. Fischerandom is Fischer's original spelling, written as one word. Chess9LX has been used as an event name, the LX being 60 in Roman numerals, so the name is 960 again. Both mean the same thing. The Chess960 glossary defines these beside the terms that genuinely change between the variant and standard chess, which are fewer than the naming suggests.
Practical advice on the names. Search for Freestyle Chess and you find events and coverage. Search for Chess960 and you find places to play, positions to study and analysis. The second is what you want if the goal is to get better.
Which name should you use?
Whichever your reader will recognise, since none of them is wrong. Discussing a tour event, say Freestyle. Filing a game with an arbiter, say Fischer Random, because that is what the regulations say. Everywhere else Chess960 carries the least ambiguity, and it is the word you will need to type to find the button on a chess site.
If you have not played a game yet, that matters more than any of this. Deal yourself an array in the position generator, check where castling would put your king and rooks, and play it against the computer. The rules are on the Chess960 rules page, castling has a page of its own because it is the one rule that had to be rewritten, and the puzzle trainer and the books cover the part of the game no amount of reading fixes.