{
  "category": "Lookup and reference functions",
  "display_name": "FLATTEN",
  "entry_kind": "built_in_function",
  "eval_api": {
    "method": "POST",
    "url": "https://handbook.dnacalc.com/api/eval"
  },
  "function_id": "FUNC.FLATTEN",
  "implementation_state": {
    "answer_bank": null,
    "detail": "Listed by Microsoft for lists and arrays in cells; no catalogue row yet.",
    "dnacalc_commit": "9e1884369a678158dd82d3d74188daf986995e87",
    "in_catalogue": false,
    "state": "refuses",
    "state_label": "Refuses or not implemented",
    "summary": "Not yet implemented",
    "workbook_corpus": null
  },
  "implementations": [],
  "json_url": "https://handbook.dnacalc.com/api/functions/FUNC.FLATTEN.json",
  "name": "FLATTEN",
  "notes": [],
  "schema": "efh.function-reference/v1",
  "section_order": [
    "what-it-does",
    "try-it",
    "quirks",
    "how-to-implement",
    "version-differences",
    "alternatives"
  ],
  "sections": {
    "alternatives": "\n- `TOCOL` and `TOROW` for ordinary two-dimensional arrays.\n- `VSTACK` and `HSTACK` to combine arrays.\n\n\n",
    "how-to-implement": "\nNo implementation exists yet. It needs arrays held in a single cell and nested arrays, which DNA Calc's value model does not\nhave, then the search or flattening rule on top. Exact matching rules should be measured in Excel first.\n\n\n",
    "quirks": "\nExcel arrays are rectangular, so uneven rows are padded. Microsoft's page does not say what a flat input does, and no\nreading is recorded here.\n\n\n",
    "sources": "\n- [FLATTEN function](https://support.microsoft.com/en-us/excel/functions/flatten-function)\n- [What's New in Excel (September 2026)](https://techcommunity.microsoft.com/blog/excelblog/whats-new-in-excel-september-2026/4549755)\n\n",
    "version-differences": "\nMicrosoft announced it in September 2026 for Insiders on Windows and Mac, with lists and arrays in cells. Its page lists\nExcel for Microsoft 365 on Windows and Mac. No Excel answers for this function are recorded here, so no comparison between Excel builds exists.\n\n\n",
    "what-it-does": "\n`FLATTEN` removes nesting from an array, so inner arrays are replaced by their contents.\n\n`FLATTEN(array, [pad_value], [levels])`\n\n- **`array`** is a nested array, or a reference to one.\n- **`pad_value`** fills gaps when rows come out uneven; without it they show `#N/A`.\n- **`levels`** is how many layers to remove, one by default. 0 removes all of them, and a number above the depth also does.\n\n\n"
  },
  "signature": {
    "display": "FLATTEN(array, [pad_value], [levels])",
    "parameters": [
      {
        "description": null,
        "name": "array",
        "optional": false,
        "repeats": false
      },
      {
        "description": null,
        "name": "pad_value",
        "optional": true,
        "repeats": false
      },
      {
        "description": null,
        "name": "levels",
        "optional": true,
        "repeats": false
      }
    ],
    "trailing_repeats": false
  },
  "sources": {
    "metadata": {
      "admission": {
        "label": "not_implemented",
        "reason": "Listed by Microsoft for lists and arrays in cells; no catalogue row yet."
      },
      "arity": {
        "max": 3,
        "min": 1
      },
      "category": "Lookup and reference functions",
      "classification": {},
      "descriptions": {
        "long": null,
        "short": "Removes nesting layers from an array",
        "short_source": "dna-calc-own"
      },
      "docs": {
        "english_description": null,
        "microsoft_url": "https://support.microsoft.com/en-us/excel/functions/flatten-function"
      },
      "entry_kind": "built_in_function",
      "localized_family_names": null,
      "localized_names": [],
      "signature": {
        "display": "FLATTEN(array, [pad_value], [levels])",
        "parameters": [
          {
            "description": null,
            "name": "array",
            "optional": false,
            "repeats": false
          },
          {
            "description": null,
            "name": "pad_value",
            "optional": true,
            "repeats": false
          },
          {
            "description": null,
            "name": "levels",
            "optional": true,
            "repeats": false
          }
        ],
        "trailing_repeats": false
      },
      "surface_name": "FLATTEN",
      "version_marker": null,
      "xlcall": null
    },
    "microsoft": "https://support.microsoft.com/en-us/excel/functions/flatten-function"
  },
  "try_it": {
    "formula": "=FLATTEN({1,2;3,4})",
    "note": "The OneCalc preview has no answer for this function: see the state above.",
    "preview_status": "worksheet-error"
  },
  "url": "https://handbook.dnacalc.com/functions/FLATTEN.html",
  "variants": [],
  "versions": []
}