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0039: Counter names ​

Status: Accepted.

Context ​

A counters line names the kind of counter as a string: counters "+1/+1" 0 -> 2, "PlayerA" counters "energy" 0 -> 2. The spec did not say how to write that name. The examples use lowercase ("time", "loyalty"), but MTGO reports Time and Loyalty. Read literally, "Time" and "time" are two kinds of counter, so the same game recorded by two writers would replay to different states, a keyframe would not match, and a viewer would show two piles of the same counter.

Decision ​

  1. A counter's name is written as the rules text names it, in lowercase, without the word "counter": "time", "loyalty", "lore", "defense", "oil", "shield", "energy". A keyword counter is the keyword: "flying", "first strike".
  2. A power and toughness counter keeps its signed form, both signs written: "+1/+1", "-1/-1", "+1/+0", "-0/-1".
  3. Poison counters are written with poison, never as counters "poison".
  4. Writers map the source's names to these forms. A name the source reports that the writer cannot map is written lowercased.
  5. Validation checks the form: a counter name with an uppercase letter, or "poison" in a counters line, fails check 1.

Rules basis ​

Checked against the Comprehensive Rules effective 2026-09-25.

  • 122.1: "Counters with the same name or description are interchangeable." A counter's identity is its name, so the format needs exactly one way to write each name.
  • 122.1a: "A +X/+Y counter on a creature ... adds X to that object's power and Y to that object's toughness. Similarly, -X/-Y counters subtract from power and toughness." This gives the signed form.
  • 122.1b: keyword counters ("flying, first strike, double strike, ...") are named by their keyword.
  • 104.3d and 120.3b: poison counters have their own rules, which is why they have their own statement (poison, section 9.5).

Alternatives rejected ​

  • Compare names case-insensitively. Rejected: it leaves two spellings of one name in files, and every reader has to remember to fold case. One written form is simpler for readers and validators alike.
  • Capitalised names, as MTGO reports them. Rejected: that is one client's display, and the rules text writes counter names in lowercase ("a time counter", "loyalty counters").

Consequences ​

  • Spec sections 7.3, 9.5, and 14.1 (check 1) state the rule.
  • Writers that read MTGO need a small name map (Loyalty to "loyalty", P1P1 or +1/+1 to "+1/+1", and so on).
  • Keyframe counter order (section 10.2, code point order of the name) is now the same for every writer.