{
  "status": "shipping",
  "advantages": [],
  "limitations": [],
  "supersedes": [],
  "supersededBy": [],
  "firstSeen": null,
  "lastSeen": null,
  "updated": "2026-10-17",
  "slug": "zstd-window-size",
  "term": "Zstandard window size",
  "aliases": [
    "Zstandard Window_Size",
    "zstd decoding window"
  ],
  "definition": "Zstandard window size is a frame parameter that bounds references into previously decoded frame data and determines decoding-history requirements.",
  "note": "Header: An ordinary frame encodes Window_Size through a window descriptor. In a single-segment frame, the descriptor is absent and Window_Size equals Frame_Content_Size. Window size in bytes is distinct from the logarithmic windowLog setting. [rfc8878]\n\nScope: The window is not a limit on total decoded output. A stream can contain many blocks or concatenate frames while requiring only bounded decoding history. [rfc8878]\n\nAPI boundary: In the pinned library API, ZSTD_d_windowLogMax limits streaming-window allocation and does not apply to single-pass decompression. It is not an exact process-wide memory ceiling. The separate CLI probe accepted 2 MiB and 4 MiB outputs under -M1MiB with small windows. [zstd-api] [hesela-resources]",
  "related": [
    "zstandard",
    "decompression-bomb",
    "compression-dictionary",
    "skippable-frame"
  ],
  "citations": [
    {
      "id": "rfc8878",
      "title": "RFC 8878: frames and Window Descriptor, sections 3.1 and 3.1.1.1.2",
      "url": "https://www.rfc-editor.org/rfc/rfc8878.html#section-3.1.1.1.2",
      "accessed": "2026-10-17"
    },
    {
      "id": "zstd-api",
      "title": "Zstandard v1.5.7 API manual: frame content size and ZSTD_d_windowLogMax",
      "url": "https://facebook.github.io/zstd/doc/api_manual_v1.5.7.html",
      "accessed": "2026-10-17"
    },
    {
      "id": "hesela-resources",
      "title": "Hesela: Zstandard decoder windows versus decoded-output budgets",
      "url": "https://hesela.com/analyses/compressed-archives-dictionary-dependencies/#resources",
      "accessed": "2026-10-17"
    }
  ],
  "provenance": [
    "General file-format and v1.5.7 API scope; no HTTP content-coding limits are inferred.",
    "CLI measurements use Zstandard 1.5.5 with synthetic data and do not measure resident memory or direct API calls."
  ]
}