FLATTEN

What it does

FLATTEN(array, [pad_value], [levels])

FLATTEN removes nesting from an array, so inner arrays are replaced by their contents.

FLATTEN(array, [pad_value], [levels])

• array is a nested array, or a reference to one.
• pad_value fills gaps when rows come out uneven; without it they show #N/A.
• levels is how many layers to remove, one by default. 0 removes all of them, and a number above the depth also does.

Try it

The OneCalc preview has no answer for this function: see the state above.

Quirks

Excel arrays are rectangular, so uneven rows are padded. Microsoft's page does not say what a flat input does, and no reading is recorded here.

How to implement

No implementation exists yet. It needs arrays held in a single cell and nested arrays, which DNA Calc's value model does not have, then the search or flattening rule on top. Exact matching rules should be measured in Excel first.

Rust code

This entry has no Rust implementation yet.

No implementation has been published with a Handbook test suite for this function.

Version differences

Microsoft announced it in September 2026 for Insiders on Windows and Mac, with lists and arrays in cells. Its page lists Excel for Microsoft 365 on Windows and Mac. No Excel answers for this function are recorded here, so no comparison between Excel builds exists.

Alternatives

• TOCOL and TOROW for ordinary two-dimensional arrays.
• VSTACK and HSTACK to combine arrays.

Named variants

No named variants are recorded yet.