Qt Creator uses the MIME type of the file to determine which mode and editor to use for opening the file. For example, Qt Creator opens .txt files in Edit mode in the text editor.
You can configure the text editor according to your needs. You can specify editor behavior either globally for all projects or separately for each project. To specify global editor behavior, select Tools > Options > Text Editor > Behavior.
To configure the text editor behavior for the current project:
Click Restore Global to revert to the global settings.
For more information about the settings, see: