File name max number of characters to upload to a Lakehouse folder

[ToddChitt]

I uploaded a file to a Lakehouse folder that was 63 characters long, including the ".xlsx" extension:

"Q1_2025 <...> Jan-Mar25.xlsx"

What Fabric named the file upon upoad was:

"Q1_202~2.XLS"

It ripped out about 50 characters from the middle of the file namen, AND changed the file extension.

It this expected behavior?

Is it a BUG?

Either way, it is EXTREMELY frustrating.

After upload I could RENAME the file back to its original just fine, but that would then mess up the Data Activator Trigger that is looking for new files in the folder of type ".xlsx".

[v-sshirivolu]

Hi @ToddChitt ,
Thanks for reaching out to Microsoft Fabric Community forum.

Thanks for sharing the details. From what you’ve described, it seems Fabric truncated your filename and changed the extension due to internal filename limits. Long filenames are often converted to the legacy 8.3 DOS format (8 characters for the name, 3 for the extension), which explains the changes you saw.

This is expected behavior rather than a bug, though I understand it’s frustrating especially if your Data Activator Trigger relies on the .xlsx extension. A few ways to handle it - use shorter filenames, adjust the trigger to accept altered names, or rename files after upload while updating dependent processes.

To avoid trigger issues, consider configuring your Data Activator to detect both original and truncated filenames, or include a consistent naming pattern that works within the filename limits.

[ToddChitt]

Do you have a link to this issue?

I have marked your answer as a solution, but really, the solution is for Microsoft to fix the issue.

And FYI: Most of your suggestions are not procticle.

Renaming AFTER upload messes up the Trigger's FileName property.

My 'defect support system' will be to tell the client to keep their filenames shorter than about 50 characters.

So frustrating to sell something like Fabric to a client, then have to turn around and tell them that something as simple as retaining a file's name AND EXTENSION during an upload is BROKEN.

[AndyDDC]

That's a purely AI generated answer. I put your question into Copilot and it generated the exact response from that reply.

Use the advice at your own discretion.

[v-sshirivolu]

Hi @ToddChitt  ,

I wanted to check if you had the opportunity to review the information provided by @jaineshp  . Please feel free to contact us if you have any further questions.

Thank you and continue using Microsoft Fabric Community Forum.

[justinjbird]

For what it's worth I attempted to upload 3 xlsx files. Different filenmame lengths - 30, 60, 70. All uploaded fine and filename intact...

[justinjbird]

Where is this known issue?

[AndyDDC]

The answer has been AI generated. We have no way of knowing whether the answer has any validity.