Understanding The “External table is not in the expected format” Error In Power Query In Power BI And Excel

Sometimes when you’re importing data from files using Power Query in either Power BI or Excel you may encounter the following error:

DataFormat.Error: External table is not in the expected format

What causes it? TL;DR it’s because you’re trying to load data from one type of file, probably Excel (I don’t think you can get this error with any other source but I’m not sure), and actually connecting to a different type of file.

Let’s see a simple example. Say you have a folder with two files: one is an Excel file called Date.xlsx and one is a CSV file called Date.csv.

Here’s the M code for a Power Query query that connects to the Excel file and reads the data from a table in it:

let
  Source     = Excel.Workbook(File.Contents("C:\MyFolder\Date.xlsx"), null, true), 
  Date_Table = Source{[Item = "Date", Kind = "Table"]}[Data]
in
  Date_Table

Now, if you change the file path in this query – and only the file path – to point at the CSV file instead like so:

let
  Source     = Excel.Workbook(File.Contents("C:\MyFolder\Date.csv"), null, true), 
  Date_Table = Source{[Item = "Date", Kind = "Table"]}[Data]
in
  Date_Table

…you will get the “external table is not in the expected format” error shown above. This is because your code is using the Excel.Workbook M function, which is used to import data from Excel workbooks, to connect to a file that is a CSV file and not an Excel workbook. The way to fix it is to use the appropriate function, in this case Csv.Document, to access the file like so:

let
  Source = Csv.Document(
    File.Contents("C:\MyFolder\Date.csv"), 
    [Delimiter = ",", Columns = 4, Encoding = 65001, QuoteStyle = QuoteStyle.None]
  ), 
  #"Promoted Headers" = Table.PromoteHeaders(Source, [PromoteAllScalars = true])
in
  #"Promoted Headers"

To be honest, if making this change is beyond your Power Query skills and you’re sure you’re trying to connect to the right file, you’re better off creating a completely new query rather than editing the query you already have.

Another common scenario where you might encounter this error is when you’re importing data from all the files in a folder and one of the files isn’t in the correct format. For example, let’s say you have a folder with three Excel files in and you use the Folder data source to import all the data from all three files:

Since all three files are Excel files the Folder option will work:

However, if you take a CSV file and drop it into the folder like so:

Then you’ll get the same error in Power Query:

Apart from deleting the CSV file you have another option to solve this problem in this case: filtering the folder so you only try to get data from the .xlsx files and no other file type. To do this, click on the step that is called “Source”. When you do this you’ll see that the step returns a table containing all the files in the folder you’re pointing at:

You’ll see that the table in this step contains a column called Extension which contains the file extension for each file. If you filter this table – which will insert a new step at this point in the query, which is ok – by clicking on the down arrow in the Extension column, delselecting the (Select All) option and selecting “.xlsx” so the table only contains .xlsx files then you can avoid this problem:

If, as in this example, the rogue file happens to be the first file in the folder and you’ve selected that first file to be your “sample” file when setting up the import, then you’ll also need to go to the query called Sample File in the Queries pane and make exactly the same change there (ie click on the Source step and filter to remove any non .xlsx files).