What is Evolution in Clash Royale?
Evolution in Clash Royale is a card form you cycle into, not a level. Why copy-deck links cannot carry it, and how DeckBeacon discloses it.
Evolution is a special form of certain Clash Royale cards. You unlock it, then cycle that card a set number of times in battle until the Evolved version hits the field. It is not "level 15 with extra stats" and it is not the same thing as Hero form.
On this site, Evolutions matter in two places: the ranked identity of a deck (an evolved Hog list is not the same playable deck as the unevolved one) and the copy step (the official link cannot turn Evolution on for you).
Form bitmasks, not levels
The official battle log fields evolutionLevel and maxEvolutionLevel look like levels. They are not. In the data DeckBeacon actually consumes they behave as form bitmasks: 1 for Evolution, 2 for Hero, 3 for both. Reading either field as "greater than zero means Evolved" was how this project once stamped a useless "Special" badge on Hero cards. Champions do not get a bit at all and have to be placed in the slot order explicitly.
That finding is why the catalog distinguishes evolutionCardIds, heroCardIds, and ambiguousFormCardIds. If the log leaves a form ambiguous, the UI says so instead of guessing. Details live in methodology and the copy-link notes on every affected deck.
Why copied decks lose their Evolutions
Supercell's link.clashroyale.com copy format carries the eight base cards and the Tower Troop. It does not carry Evolution or Hero form. This is not a DeckBeacon bug and not a RoyaleAPI bug. Any tool using the official handoff has the same gap.
DeckBeacon's rule: if a ranked deck uses Evolutions, the page and the row both list the cards to set by hand, in the open — never behind a tap, because the copy path cannot be gated. Walkthrough: how to set Evolutions after copying.
Filtering by Evolution count
The deck browser can restrict lists by how many Evolution cards they play. That count is evolutionCardIds.length. Hero-form cards are a different facet; collapsing them into "has a special form" is how the bitmask bug came back. If you want lists with no Evolutions, use the decks without Evolutions use case as a starting point, then filter.