Modify failure message when uploading file

[e-no91]

Which file should I edit to modify the failure message when uploading file, as shown in the image?

[sanjaybandhaniya]

You have to modify upload.post.js file to modify the failure message when uploading file
config\alfresco\extension\templates\webscripts\org\alfresco\repository\upload\upload.post.js

It is not recommended to directly edit upload.post.js file.instead of that use module extension pattern.

Surf Extension Modules | Alfresco Documentation