Power BI User-Defined Functions

In Power Query (M), you can define your own functions and reuse them across queries. User-defined functions (UDFs) keep logic in one place and make complex transformations easier to maintain.

Defining a function

In the Power Query Editor, create a new blank query and write an M function that takes parameters and returns a value. Once saved, the function appears in the query list and can be invoked from other queries. Use them for repeated parsing, formatting, or lookup logic.

Be aware that not all operations inside a UDF fold back to the source; test with View Native Query when performance matters.