Free MTG Playtester for the Browser
Goldfish a deck. Test a brew. Try a sideboard plan. Run a matchup ten times. All in your browser, free.
What the playtester does
TCG Playsim is what "playtest mode" used to be on the old Cockatrice / Untap clients, but with no download and a much nicer UI. You build a deck from any cards Scryfall knows about — including digital-only sets, Un-cards, Conspiracy cards, and homebrew via the Custom Card Forge. Then you sit down and play it, manually, the way you would on a table.
The app keeps the bookkeeping clean: life totals, the stack with reactivity, mana pool, counters per card, tokens, copies, scry / surveil prompts, mill counters, exile, command zone, sideboard. Hotkeys for everything: D draw, U untap-all, S shuffle, F search any zone, G scry, ? for the full hotkey list.
Goldfishing solo
Click New Deck, build it, click Play. You're in a single-seat game with full controls — draw, mulligan, play turns, observe what your deck actually does in practice. The gameplay log records every action so you can scroll back to see exactly what happened on turn three. No account needed to playtest solo — your decks save in your browser.
Playtesting against an opponent
Click Multiplayer → Host. Share the room link with your friend. They open it in their browser — desktop or mobile — and they're in. No download, no install, no account creation friction. You play the matchup, then re-shuffle and play again. The whole loop is built around fast iteration: testing a deck against a meta opponent ten times in 40 minutes is the point.
Formats covered
Standard, Commander (EDH), Oathbreaker, Modern, Pioneer, Pauper, Legacy, and the shared-deck Dandân format. Format is set per-deck in the deckbuilder — Commander gets a command-zone slot, Oathbreaker gets planeswalker + signature spell slots, Dandân uses a single shared library. Custom and homebrew formats work too — the playtester doesn't enforce format legality, you do.