Film Room

What it reads

MTG Arena writes a log file, Player.log, as it runs. With Detailed Logs switched on (Arena's own setting), the log carries the messages between the game and Arena's servers as JSON. Film Room reads four kinds:

• The match room: the match, the event (ranked best of one or three, a draft, and so on), both players' names and seats, and at the end the winner of each game and of the match.
• The game engine's game states: the game number, the turn number and whose turn it is, each player's mulligans and life, and each card on the table, in a graveyard, in exile or revealed, by its Arena card id and owner. Each move of a card carries a zone transfer note from the engine: its kind (a land played, a spell cast, a card drawn, countered, destroyed, sacrificed or dealt lethal damage) and the zones it left and entered. Those notes are the replay timeline's plays. Arena sometimes holds a game state back and sends it a moment later as a queued game state; it has the same shape and carries plays and life of its own, so Film Room reads both kinds, as 17Lands' log client and manasight-parser do. An edict (a message the server sends for you when a timer runs out, in the shape of the one you'd have sent) is read as that message.
• Your deck: the list Arena loads for game one, and the list you submit after sideboarding for games two and three.
• The deck you chose for the event, for its name.

Everything else in the file, including your account details and sign-in token, is skipped and never kept. The file is read on this device a few megabytes at a time; nothing is uploaded.

How each number is worked out

On the play or the draw: whose turn turn 1 is (for a game conceded before turn 1, the player active while the mulligans are decided, where 17Lands' log client reads it). Mulligans: the highest mulligan count the game states show for each player before the game starts. Result: the winner the game states and the match room report for each game; a game whose result isn't in the log (Arena was closed mid-game) is left unfinished. Cards they showed: every card object their seat owns that appears in the log, with the first turn it appeared (face-down cards and tokens are skipped), so it's what they played, discarded, revealed or had exiled, not their whole deck.

games won on the play = games won when you took turn 1 / games you took turn 1

Every rate shows its 95% Wilson range beside it (the math is on the pages of Decks and My Stuff), in whole percents, with one decimal where a number would otherwise round to 0% or 100% (0.4%, not 0%), and match win rates count wins over wins and losses, with draws shown apart. "Send results" puts each finished match into the linked deck marked Arena log, with the event, best of one or three, play or draw in game one, and the deck version saved before the match's date. The opponent's screen name stays in Film Room: a deck's record says what they played, never who. A match already in the deck (the same Arena match id, or the same start time) is never added twice, and one sent before that isn't in the deck now (you deleted, corrected or moved it) is left out unless you choose "send them again".

Arena ids become names through 17Lands' public card list and Scryfall's Arena ids. A card newer than those lists shows as its Arena id until the site's card data next updates.

The luck audit

Your own hand is visible in the log: each seven you're dealt shows in your hand while Arena waits for your keep or mulligan, and every card that comes to your hand afterward arrives with a new card id. Film Room keeps, per game, every seven you were dealt and the cards that came in after the seven you kept, in order (up to 12), as Arena card ids. A land is any card you can play as your land drop.

Two samples are honest ones. Every seven you were dealt, mulligans included, is a random seven from the whole deck (N cards, L lands). The cards drawn after your keep are a random sample of the library that seven left behind: N - 7 cards with L - k lands, where k is the lands in the seven you kept (cards you bottom go under everything). The seven you kept is never judged against the deck, because you chose it: keeping only two to five landers would otherwise read as drawing hot, more so the more games you log. In each sample the number of lands follows the hypergeometric distribution (drawing without replacement):

P(k lands in n cards) = C(L, k) x C(N - L, n - k) / C(N, n)

expected lands = n x L / N; variance = n x (L / N) x (1 - L / N) x (N - n) / (N - 1)

Over many games the lands you saw are compared with the sum of the expected counts, in standard deviations (z), and the chance of a gap that big either way comes from the normal curve. Each check (mulligans by Karsten's keep rule of 2 to 5 lands in seven, screws at 2 lands or fewer in the first 10 cards, floods at 8 or more in the first 13, and draws after the keep in the lowest or highest tenth of outcomes) is compared with its expected count and a 95% range. Screws and floods count the kept seven, so each game's chance of one is worked out from the seven actually kept and the library left behind: the sum of each game's chance, plus or minus 1.96 standard deviations. Scry, surveil, tutors and cards returned to your hand make the real sample drift a little from these pure odds.

"Wins and losses, by what your draws were" is a count table: your losses and your wins, each split into games with a land-light, land-heavy, screwed or flooded draw, games with none of those, and games with under 3 draws after the keep. Those three columns split the games; the last column, games where they mulliganed, counts games from any of them again. It counts; it doesn't say what decided a game.

The mulligan table's note puts Frank Karsten's simulated 10 to 15 point cost of a mulligan to six beside your own two win rates, each with its 95% Wilson range, and the difference between them with its 95% range (Newcombe's method, built from the two Wilson ranges). A few games give a range far wider than Karsten's figure, and the note says whether the range holds, overlaps or misses it.

The replay timeline

Each game opens as a timeline, turn by turn. From a log read with the plays in it, every card move the engine noted is placed at its turn: land drops, spells cast, your own draws (theirs are hidden from you, so they aren't there), and cards that went from the battlefield to a graveyard, to exile or back to a hand, plus countered spells. Whose card it was comes from the card's owner in the game state. Life is the total the game states show at the end of each turn, written as the change that turn. Attacks and blocks aren't noted as moves, so they're yours to add. A game read before Film Room kept plays starts from what it did keep: the mulligans, the turn each of their cards first showed, and the final life; bringing the same log in again fills in the plays.

The chart draws both life totals by turn, and it is the turn slider: drag across it, or use the arrow keys, Home and End. A turn's list holds what happened in it, in order, and you can add plays (whose card, then what: land, cast, attacked, blocked, died, exiled, countered, drew), notes and marks for review, change life by steps or by typing the total, and undo. Enter adds a named card as a land when it can be played as a land drop and as a spell otherwise, and plain words as a note. Nothing from the log is saved until you change it; your version is kept in this browser with the rest of Film Room and rides along in My Stuff's backup.

"Copy as text" writes one line per play under a line per turn, and that text (it starts with "# Film Room replay timeline") reads back exactly as it was: every play, life change, note and mark, with notes read word for word, even ones that mention life or turns. Each line is checked as it's written; a card name that would read back as something else (one with a parenthesis in it, or one spelled "a card") is written in quotes. A narrated game reads the same way as far as it can: a line starting "Turn 4" starts the turn, "I" or "you" and "they" or "them" say whose card it is, a verb says what happened, "I'm at 14" or "they're at 9" sets life, and a line it can't read is kept word for word as a note on its turn. A number followed by what it counts ("I'm on 3 lands", "they're down to 2 cards", poison, counters, mana and the like) isn't read as life. A card is named only when the words are its whole name or front face (case and accents aside), or the part before the comma of exactly one card in this match (Kaito, for Kaito, Bane of Nightmares); other words stay with the play as its note, so "they attack with a Goblin" reads as an attack with the note "a Goblin". For a card that died, was exiled, countered or returned, whose card it was comes only from "my" or "their", since the one who did it may not own it. Text copied from Player.log is read as a log, and the plays for the match on screen come from it. A timeline holds what was logged or typed; it never judges a play.

Limits, each said on the page where it applies: Film Room keeps up to 2,000 plays a game from the log (a game with more says from which turn they're missing), a timeline holds 200 turns and 500 entries a turn, undo reaches back 200 changes ("back to the log's version" is there at any time), and a typed life total is a whole number from -999,999 to 999,999 (a number outside that, or with a decimal, is changed to fit and the page says so). A typed total is set on Enter or when you leave the box, however you leave it: tapping +1, a chip or next right after typing sets the total and then does what you tapped.

Two tabs. Every change is written, under a lock the site's tabs share (the Web Locks API), to the copy stored at that moment, so a change made in another tab is kept, not written over, and the other tab shows it. When two tabs change the same game's timeline at once, additions from both (plays, notes, life) are kept, and the tab says so; a change that would go over the other tab's (a removal, a paste, going back to the log's version) isn't kept, and the tab says so and shows the other tab's version. Undo in one tab never reaches past a change made in another: the tab says nothing was undone. A My Stuff backup restored here is merged with Film Room's history match by match: matches, notes, deck links and timelines only in the backup come back, the ones here stay, and a timeline changed in both keeps the one changed last.

Your cards: opening hand, drawn and kept

For one deck at a time, from the games whose opening hands are in the log, each card's games are split two ways. In the opening hand: the hand you started turn 1 with, which is the seven you kept less any cards you put on the bottom (a game read before Film Room kept that hand counts the whole seven, and the page says how many). Drawn: in the opening hand or among the first 12 cards that came to your hand after it. For each split the page gives the games on each side, the win rate on each side with its 95% Wilson range, and the difference between them with its 95% range (Newcombe's method, built from the two Wilson ranges):

difference = wins with it / games with it - wins without it / games without it

When that range includes zero the row says it can't tell yet. The two rates' own ranges can overlap a little even when the difference's range clears zero; the difference's range is the one that answers whether the two rates differ. Kept sevens: of the sevens you were dealt with at least one copy, the share you kept, with its range. Rows sort by a number the page names, games with the card by default, since that is the sample behind each rate; no card is labeled as helping or hurting.

What shapes these numbers, said on the page too: you chose which sevens to keep, so games with a card in the opening hand are games where a hand holding it was kept; longer games see more cards, so drawn rates lean toward however this deck's long games went; a card counts only in games it was in the deck, so sideboarded games count for the cards in the deck that game; and with many cards compared, about 1 in 20 ranges sits clear of zero by chance alone. The table of hands you kept by size (seven, six, five, four or fewer) counts every decided game of the deck, with the share of games and the games won at each size, each with its range.

HSReplay and HSGuru show the same kind of numbers for Hearthstone decks (win rate when a card is kept in the opening hand and when it is drawn), with the counts shown.

Naming their deck

For Standard and Explorer matches, their nonland cards are compared with Meta Lens (Explorer against its Pioneer decks, the nearest format it tracks): for each archetype, the share of its decks from the 75 days before the Meta Lens data ends that run each card. A card is one of an archetype's regulars when at least a quarter of its decks run it. Their deck gets the archetype whose regulars cover the most of what they showed, when that's at least two cards and at least 60% of them; otherwise it's named by the colors of the cards they showed. It's a guess from a handful of cards, and the match page says which cards it was based on. Meta Lens decks come from Magic Online events, so an Arena-only brew can land on the nearest archetype played there.

Limits worth knowing

Arena starts a new Player.log each time it launches and keeps only the one before, as Player-prev.log, so bring your log in after each session; Film Room keeps everything you bring in. When a game state is very busy, Arena sometimes writes a summary instead of the full state, and a few of their cards can be missing; Film Room tells you when a log had any. Under about 30 matches, play and draw splits are mostly noise.

Companions are untested. We have no Arena log that shows a companion put into a hand (manasight-parser's test data has a companion marked at the start of a game, not the move), so how Film Room reads that move isn't checked. If Arena writes it as it writes other cards coming to a hand, the companion counts as a card that came to your hand, in the luck audit's draws and the card lens, and casting it shows on the timeline as a spell cast.

This week on Arena

The event desk opens with a calendar for the current set, entered by hand from Wizards' own pages (their terms bar scraping, and nothing is read from them while you use the page): the Reality Fracture event schedule (September 21, 2026), the Qualifier Play-In and Qualifier Weekend information (September 3, 2026), the Arena Limited Championship Qualifier terms (page of October 13, 2026, last updated October 8) and the Arena Direct page for the Reality Fracture Play box Direct, all checked October 18, 2026. Dates are the days Wizards lists, in Pacific time; start and end hours vary by event. Today is the date in Pacific time, the time zone of Wizards' dates (the device's date where the browser can't name a time zone). On now lists the events whose first day is on or before today and whose last day is on or after it, ending soonest first; Starting in the next 7 days lists those whose first day falls in the coming week; the whole calendar is folded below them. Each row can value an entry in the calculator (when its event's payout is in the table), show its row in the table, or open Draft Sim on the set when Draft Sim has it. Rows whose payout Wizards' schedule doesn't give (Flashback and Alchemy Premier Drafts, the cube, bot drafts) say so. Past the set's season the desk says the next set's events aren't entered yet while later qualifier rows still show; past the last row, that the calendar has ended.

The road to an invitation

Three paths, each a qualifier and the events its top result leads to, worked out together at one chance of winning a game, g, which you type. A best-of-one match is one game; a best-of-three match is won 2-0 or 2-1 with each game independent:

best-of-three match won = g^2 x (3 - 2g)

Arena Limited Championship Qualifier: Draft 1 (5,000 gems or 25,000 gold, any number of entries; best of one to 7 wins or 2 losses; 4 wins 1,000 gems, 5 wins 2,500, 6 wins 5,000, 7 wins 5,500 and a Draft 2 token), then Draft 2 (by token; best of one to 6 wins or 2 losses; 1 to 4 wins 6,500, 7,500, 8,500 and 10,000 gems, 5 wins $1,000 and an invitation, 6 wins $2,000 and an invitation), from Wizards' terms, last updated October 8, 2026. Best-of-one Qualifier Play-In (6 wins or 2 losses) or best-of-three Play-In (4 wins or 1 loss), each 4,000 gems, 20,000 gold or 20 Play-In Points, whose top result is a Qualifier Weekend token, then the Qualifier Weekend: Day One, best of three to 7 wins or 3 losses, 500 to 12,000 gems by wins and a Day Two token at 7; Day Two, best of three, 750 gems at 0 wins, 1,000, 2,000 and 3,000 gems with a token for next month at 1 to 3 wins, and an Arena Championship invitation at 4 (Wizards, September 3, 2026). Wizards' page gives Day Two as four wins or two losses in its prize table and as six wins or two losses in one later line; the prize table's is used.

Each step's chance of every final record is the negative binomial for an event that ends at W wins or L losses, at the step's match win chance p:

P(k wins) = C(k + L - 1, k) x p^k x (1 - p)^L for k below W; P(W wins) = sum over l from 0 to L - 1 of C(W - 1 + l, l) x p^W x (1 - p)^l

reach(first step) = 1; reach(next step) = reach(this step) x P(this step's top result)

expected gems = sum over steps of reach x sum over k of P(k wins) x gems(k); expected cash the same with dollars

P(invitation from one entry) = sum over steps of reach x P(a result that awards an invitation)

net gems an entry = expected gems - entry in gems

entries for one invitation, on average = 1 / P(invitation); gems spent net along the way = (entry - expected gems) / P(invitation); half of players need ceil(ln 0.5 / ln(1 - P(invitation))) entries or fewer

entries your Play-In Points pay for = floor(points / 20); P(at least one invitation), each entry in a different month = 1 - (1 - P(invitation))^entries; all in one month = (1 - (1 - P(Play-In token))^entries) x P(invitation | token), since a Qualifier Weekend token past the first is redundant

Counted: gems, and Draft 2's cash, shown apart and never turned into gems. Not counted: the next month's tokens from 1 to 3 wins on Day Two, the championship's own prizes, and the time it takes. An entry paid with points costs no gems and has the same chances. Wizards says tokens earned past the first in the Play-Ins are redundant. The same one chance a game holds at every step and every record; at high records the opponents are players who also won, so a real player's chance there can be lower, and these numbers then run high; each event's row in the table carries its sources and the day it was checked.

Plans and practice

For each match on a saved deck: what you brought in and took out, beside the sideboard plan saved on that deck for the matchup (from Matchup Lab, Prep or Decks). An Arena match's changes are read from the log: the deck you submitted for game two against the deck's main deck, card by card. A paper match's are typed: pick the match, then the cards in and out. A plan kept by seat is read for game two's seat; a side of the plan with nothing in and nothing out is no plan for that seat, so such a match is in neither count. Game two's seat is never guessed: Decks logs game one's seat only, and after game one its loser chooses (MTR 2.2), so a match with no seat on record waits for one before it is set beside the plan. Each match says it went as planned, or which cards came in or went out that the plan doesn't have and which the plan has that didn't. Over many matches the page counts the matches that followed the plan, the record each way with its 95% Wilson range and the difference's Newcombe range, and the cards that differ most often. These are facts about what was done; the page doesn't say which was right.

Between games: a card with the plan for the matchup, on the play or the draw, and a note, to look at before game two. Magic Tournament Rules 2.11, in our words: between games you may look at short notes written before the match (a sheet or two at most), and notes taken during the match may be read while it lasts; notes on an electronic device are allowed only at Regular Rules Enforcement Level, so at an RCQ (Competitive) the card says to print the plans and keep game notes on paper.

Sources

• Wizards of the Coast, "Creating Log Files on PC/Mac/Steam" (MTG Arena support, updated July 9, 2026): the Detailed Logs setting and where Player.log lives; the same page notes that community tools read this file.
• The log's message shapes, from the Arena client's own output and the open documentation of community log readers: manasight-parser (MIT and Apache licensed; its game state module, read September 26, 2026: "QueuedGameStateMessage wraps a deferred game state update with the same structure"). Film Room's reader is its own code.
• Queued game states and edicts: 17Lands' log client, mtga-log-client (the seventeenlands package, GPL 3.0), which keeps both GameStateMessage and QueuedGameStateMessage in its game history, reads an edict as the client message it carries, and reads the starting player from the active player while mulligans are decided.
• Card ids: 17Lands public card list (CC BY 4.0) and Scryfall's arena_id field.
• Mulligan cost for scale: Frank Karsten's mulligan simulations (ChannelFireball and TCGplayer articles).
• Zone transfer notes and their kinds: the Arena client's own log output, and MTGATracker's open log reader (MIT licensed), which reads the same notes for its game history.
• The opening hand read in turn 1's beginning phase, after any cards went to the bottom: the same point 17Lands' open log client (the seventeenlands package) reads it.
• Card numbers from your own games in the same form: HSReplay, "Card Mulligan Data" (July 23, 2020) and HSGuru's stats explanation (mulligan and drawn impact, with the counts).
• Robert G. Newcombe, "Interval estimation for the difference between independent proportions" (Statistics in Medicine, 1998), method 10: the range of a difference, built from two Wilson ranges.
• Wizards, Reality Fracture MTG Arena event schedule and achievements (September 21, 2026): the calendar.
• Wizards, Qualifier Play-Ins and Qualifier Weekend information (September 3, 2026): Play-In entry, structure and dates; Qualifier Weekend structure and prizes; Play-In Points.
• Wizards, Arena Limited Championship Qualifier terms and conditions (page of October 13, 2026, last updated October 8): Draft 1 and Draft 2.
• Wizards, Arena Direct for Reality Fracture (read October 18, 2026): the Play box Direct's dates and prizes.

The event desk

Each event's entry and payouts come from the site's one hand-kept Arena event table (cards/limited/arena_events.json), which the Wildcard Planner's packs and sets tab reads too. Each row carries its sources, a status (official, secondary, or conflicting with both values shown) and the day it was checked (October 17 or 18, 2026); payouts can change in the client. Since October 18 the table also holds the Arena Limited Championship Qualifier's two drafts, both Qualifier Play-Ins and both days of the Qualifier Weekend; Draft 1 is in the calculator, and the others are valued together on the road to an invitation. For an event that ends at W wins or L losses, the chance of each final record follows the negative binomial; Traditional Draft plays all three matches, so it is binomial. Expected value adds each result's gems and its packs times the pack value you set (200 gems, the store price of a pack, unless you change it); mythic packs count as packs, a chance of an extra pack counts as that fraction, and boxes, cards kept, Play-In Points and titles aren't valued. The break-even win rate is where the expected value crosses the entry, found by bisection. Your own win rate counts the decided matches Film Room holds for events of that kind, with the 95% Wilson range. The chance of running out draws each entry's result from those exact chances, 10,000 runs from one seed (fewer when the entries are many: at most 1,000,000 draws, never under 1,000 runs; the page states the runs and their margin). Matchmaking pairs by record and rank, so a rate measured against a mixed field may not hold at high records.