Add a thumbnail column for documents and media in a SharePoint Online document library

Mark Rackley recently tweeted about the ability to create a calculated column in SharePoint online document libraries that would automatically render thumbnails for documents. In the GIF from his tweet, it shows how this works for media files.

Naturally curious, I had to see how this worked for documents of .docx, .pdf, .pptx, etc. types. What I found is that it only currently supports some file types:

Supported file types (there’s likely even more I didn’t test):

  • Word (.docx)
  • PDF (.pdf)
  • Emails (.msg)
  • Images (.png, .gif, .jpg, etc.)
  • Media (.mp4)

Not-yet-supported file types:

  • Excel (.xlsx)
  • OneNote (.one)
  • PowerPoint (.pptx)

Create a thumbnail column in SharePoint Online document libraries

1. Add a new column to your document library (library settings > Create column).

2. Set the column name to Thumbnail. As for type, you have two options:

  • Leave type as Single line of text. Thanks to Dario Cassinerio for sharing that Single line of text type works as well as (and more simply than) Calculated set to [Title].
  • Mark Rackley suggests sticking with Calculated set to [Title] (see example screenshot) to prevent users from editing the text field in forms.

3. Click OK.

Supported file types will have thumbnails rendered (like .docx and .pdf in the example below) and others will just be blank (like .pptx and .xlsx in the example below).

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Here is an animation demonstrating the entire process, start to finish using Single line of text as column type:

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And another animation but using the Calculated column set to [Title] type:

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SharePoint column validation format difference between classic and modern experiences

The following column validation formula worked fine in SharePoint on-prem (2016 specifically, in my case), but returned an error when used in the exact same context in SharePoint Online’s modern UI:


The expected behavior, in SharePoint Server/on-prem OR SharePoint Online/O365, is that if someone enters a date beyond the current date, they’ll get an error message and cannot submit the form until it’s corrected and the validation formula resolves to TRUE.

Troubleshooting in SharePoint Online

I used this formula in SharePoint Server/on-prem, and it worked fine. Then I tried using the modern UI in SharePoint Online by using the column’s menu > Column settings > Edit.

But when you try to save the exact same formula (specifically from the modern experience side panel) you get the error “A formula has a syntax error.”

Then I decided to try the classic view of settings to compare on-prem and online as closely as possible. I went to Settings > List settings and selected my column.

And, as you already know, it WORKED when entered on this classic column settings page (in SharePoint Online still) instead of the modern column settings side panel accessed directly from the list view.

When I go back through the modern UI now that my formula saved successfully, I see what caused the problem. The modern UI requires that you begin the formula with an equals sign (=). When I created the formula through the classic column settings method, it automatically added the equals sign for me in the background.


So if you’re creating column validation formulas in the modern experience (or even in classic), just remember to add an equals sign (=) to the start of your formula.

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The difference is simply which formats are accepted.

  • Classic: Start formulas with or without equals sign
  • Modern: Start formulas with equals sign