> ## Documentation Index
> Fetch the complete documentation index at: https://docs.cromos.so/llms.txt
> Use this file to discover all available pages before exploring further.

# The expansion object

> A set of cards released together.

An expansion is a set released together — Base Set, 151, Evolving Skies. It belongs to exactly
one [series](/series/object), and every [card](/cards/object) belongs to exactly one
expansion. Ids are upstream's: `base1`, `sv03.5`, `swsh7`.

## Counting cards

Two counts, and they disagree on purpose:

<ResponseField name="card_count_official" type="number | null">
  The printed set size — the number on the bottom of the card. Excludes secret rares.
</ResponseField>

<ResponseField name="card_count_total" type="number | null">
  Everything the expansion actually contains, secret rares included.
</ResponseField>

A card numbered 199/165 is not a mistake: 165 is official, 199 is inside total. 151, the set
below, contains exactly that card — `sv03.5-199`, a Special illustration rare Charizard ex,
sits inside a 207-card total against a 165-card official count.

## Legality

`legal_standard` and `legal_expanded` say whether the expansion is tournament-legal in each
format. `null` means unknown rather than illegal — it is what upstream sends when a set has no
legality data at all, not a claim that the set is banned.

## Example

```json theme={null}
{
  "data": {
    "id": "sv03.5",
    "series_id": "sv",
    "name": "151",
    "logo": {
      "low": "https://assets.cromos.so/expansions/sv03-5/logo/low.webp",
      "high": "https://assets.cromos.so/expansions/sv03-5/logo/high.webp"
    },
    "symbol": "https://assets.cromos.so/expansions/sv03-5/symbol/image.webp",
    "release_date": "2023-09-22",
    "card_count_total": 207,
    "card_count_official": 165,
    "legal_standard": false,
    "legal_expanded": true
  },
  "error": null
}
```