Excel Dynamic Arrays vs CSE Formulas in 2026: The Complete Migration Guide

If you have been using Excel for more than a few years, you are probably familiar with the old Ctrl+Shift+Enter trick for array formulas. But in 2026, those legacy CSE (Control-Shift-Enter) array formulas have been largely replaced by a far more powerful and intuitive system: dynamic arrays and spill formulas. This guide will help you understand the difference, migrate your old formulas, and unlock the full power of modern Excel array functions.

What Are CSE Array Formulas and Why Are They Being Phased Out?

CSE array formulas were introduced in Excel decades ago as a way to perform calculations across multiple cells simultaneously. You would type a formula and press Ctrl+Shift+Enter instead of just Enter, which wrapped the formula in curly braces like {=SUM(A1:A10*B1:B10)}.

The problem with CSE formulas was that they were fragile, hard to audit, and confusing for anyone who did not create them. They did not automatically resize if your data grew, and they required you to select the exact output range before entering the formula. In 2026, Microsoft has fully committed to the dynamic array paradigm that was first introduced in 2019, and most workplaces have now made the switch.

Understanding Dynamic Arrays and the Spill Concept

Dynamic arrays work on a fundamentally different principle. You enter the formula in a single cell, and Excel automatically spills the results into as many cells as needed. No Ctrl+Shift+Enter required. No pre-selecting a range. If the data changes and the output grows or shrinks, the spill range adjusts automatically.

The blue border you see around a spill range in Excel 2026 is called the spill indicator. You can reference the entire spill range in other formulas using the # operator. For example, if a UNIQUE formula in cell D2 spills results downward, you can reference the entire output with D2#.

The Core Dynamic Array Functions You Need to Know

UNIQUE

The UNIQUE function extracts a distinct list from a range, eliminating duplicates automatically. In the old world, you needed Power Query or a complex array formula to do this. Now it is just one formula: =UNIQUE(A2:A100). You can also sort the output by wrapping it with SORT: =SORT(UNIQUE(A2:A100)).

SORT and SORTBY

The SORT function sorts a range dynamically. Unlike the old Data > Sort command, SORT creates a live sorted output that updates whenever the source data changes. SORTBY lets you sort by a column that is not part of the output, which is perfect for dashboards and reports.

FILTER

The FILTER function is one of the most transformative additions to Excel. It replaces complex Advanced Filter setups with a single formula. For example, =FILTER(A2:C100, B2:B100="London") returns all rows where column B says London. You can add multiple conditions using * (AND) or + (OR) logic between criteria arrays.

SEQUENCE

SEQUENCE generates a dynamic array of sequential numbers. This is useful for creating numbered lists, date series, and complex index arrays for other formulas. =SEQUENCE(10,1,1,2) creates a column of 10 numbers starting at 1 and incrementing by 2.

How to Migrate Your Old CSE Formulas

Converting legacy array formulas to dynamic array equivalents is usually straightforward. Here is a step-by-step approach:

Open the workbook and enable iterative calculation warnings if prompted. Excel 2026 will flag any CSE formulas it detects.

Click on a cell that contains a CSE formula (identified by curly braces in the formula bar).

Identify what the formula is trying to do: is it filtering, summing conditionally, or extracting unique values?

Replace it with the appropriate dynamic array equivalent. For example, a CSE formula like {=IF(B2:B10>100, A2:A10, "")} can often be replaced with =FILTER(A2:A10, B2:B10>100).

Delete the old formula and enter the new one in a single cell without pressing Ctrl+Shift+Enter.

Verify that the spill range covers the correct area and that downstream formulas referencing these cells still work.

Using the Spill Reference Operator (#) in Your Workbooks

One of the most powerful concepts in modern Excel is the spill reference. Once a formula spills its results, you can refer to the entire spill with the hash symbol. This is especially useful when building dashboards that feed from dynamic lists.

For example, if your UNIQUE formula lives in E2 and spills customer names down the column, you can build a dependent FILTER formula that references E2# as its criteria. When a new customer appears in your source data, the UNIQUE list updates, and so does everything downstream.

In Copilot-assisted Excel 2026, you can simply describe the relationship you want and Copilot will suggest the appropriate spill-aware formula. This makes complex multi-formula setups accessible even to beginners.

Troubleshooting Common Spill Errors

The most common issue with dynamic arrays is the #SPILL! error. This occurs when the spill range is blocked by existing content. To fix it:

Clear any data or formatting in the cells directly below or to the right of your formula cell.

Check for invisible characters or spaces in cells that appear empty but are actually occupied.

If you are working inside a structured Excel Table, note that spill formulas do not work within table ranges. Move the formula outside the table.

Excel 2026 Copilot and Dynamic Arrays

Microsoft Copilot in Excel 2026 has deep integration with dynamic array functions. When you ask Copilot to analyze your data, it frequently builds FILTER, UNIQUE, and SORTBY formulas behind the scenes. Understanding how these work will help you edit, refine, and extend the formulas that Copilot generates.

You can also prompt Copilot with questions like 'Show me all sales above $10,000 sorted by date' and it will build the equivalent FILTER and SORT combination for you. The ability to read and understand the resulting dynamic array formula means you can customize it further without starting from scratch.

Conclusion: Embrace the Dynamic Array Revolution

The shift from CSE array formulas to dynamic arrays represents one of the biggest quality-of-life improvements in Excel's history. In 2026, there is very little reason to use the old Ctrl+Shift+Enter approach. Modern dynamic array functions are more readable, more powerful, and far easier to maintain.

Start by identifying your most complex CSE formulas and rewriting them with FILTER, UNIQUE, SORT, and SEQUENCE. You will find that what once required a complex multi-cell array formula can now be expressed in a single, elegant, self-resizing formula. Your future self and your colleagues will thank you.

Have questions about specific CSE formulas you are trying to migrate? Drop them in the comments below and we will help you find the dynamic array equivalent.