Which file type deletes all formatting?

The file type that deletes all formatting is the .txt file. Text files are designed to store plain text without any additional formatting such as fonts, colors, or styles. This means that the content within a .txt file is unadorned and retains only the character data, making it universally compatible and easy to edit in any text editor or word processor.

In contrast, the .doc file format, used by Microsoft Word, supports various formatting elements like font styles, images, tables, and other features that enhance document presentation. The .pdf format is primarily used for preserving the format of a document as it appears in its original layout across different devices and applications, which includes typography and graphics. The .mp3 file is an audio file format that contains sound data and does not involve text formatting at all.

Thus, the .txt file is the only option that expressly eliminates all formatting, allowing for straightforward, unformatted text storage and use.