Need to pass the file to power automate flow which was uploaded by the user in copilot studio

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Posted on by atharva.bhagat

I have asked user to upload a file using the "Ask question" card. The entity type I have kept as "File" and stored it in a variable called "varFile"

Now I have created a power automate flow which has an input of type file. When I call this flow from copilot studio and pass my variable "varFile" - it says the PA flow input is a record and my variable varFile is a blob. (Which is true indeed - it's a file) But then how do I pass it to power automate flow ?

I couldn't find any function to convert this blob variable into string. (Tried with Text function but didn't worked)

Also there is no support of function base64/uriEncoded or similar kind of functions which are available in power automate.

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JasonAbba 51 on at

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Hello @CU11031819-0,

You can convert your record to text. There is an undocumented called SetText Node in Copilot Studio. It can take any datatype as input and convert it to String. This text variable can be passed to PA and then PA can use the Base64 Conversion expressions to do what you desire.

I have documented the use of this SetText node on my LinkedIn post, please refer to it solve your issue: https://www.linkedin.com/posts/jasonabba_copilotstudio-aibuilder-yaml-activity-7276900081876746242-lPu8?utm_source=share&utm_medium=member_desktop&rcm=ACoAAB7wv4QBRDsqilcJB_pRFiXp2GdXYP43uh8

Microsoft Copilot Studio's Product Team should really make this feature discoverable :)

Thanks.

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atharva.bhagat 4 on at

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Thanks @JasonAbba for your response!!

Adding a node which is un-documented using the YAML code was something new which I learnt here.

However that does not solve the problem.

SetText Node worked fine for the record variable. However when I try it with my "varFile" which is a blob it returned me a blank string.

Just wondering if there can be some un-documented node which plays with the "File" variable.

Would you mind sharing from where I can explore more on these YAML codes ? Like is there any documentation for that.

Appreciate your time and help !!

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Vinoth Selvam 1,592 Super User 2025 Season 1 on at

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Hi CU11031819-0,

There are no direct functions to convert this blob variable into string and no support of function base64/uriEncoded.

i havent tried the below, but u can check if this works.

Instead of passing varFile directly, use this format:

{ "Name": varFile.name,
"Content": varFile,
"ContentType": "application/octet-stream" }

In Power Automate: Set the input type as "File". The Power Automate trigger should be expecting a record, not just a file.

Inside Power Automate, access:

triggerBody()?['Name'] → File name

triggerBody()?['Content'] → File content

triggerBody()?['ContentType'] → File type

If your downstream system requires Base64, use base64(triggerBody()?['Content']) in Power Automate.

Thanks.

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