Does a cotton blanket for daytime use need tzitzis?

Question

Regarding blankets, standard practice is that we don't attach tzitzis and we don't round off any corners.

Reddit user ShamanSTK asks:

I have a blanket on the couch with four corners which is almost used exclusively for day time use. It is not a blanket slept with and it is used solely for warmth when I don't feel like turning on the heat. Does it need tzitzis?

In the case of a wool blanket in the daytime, this link says to round one corner. What if ShamanSTK's blanket is made of cotton? Must he round one corner? Must he attach tzitzis?

Answer 1

Indeed one does not attach tzitzit to a blanket, whether cotton or wool

R Jonathan Blass at yeshiva.co notes

It does not need Tzitzit (Shulchan Aruch Orach Chayim 18, 2). Some say the reason is because the main use of the blanket and sheet is at night; others explain that only something worn as a garment needs Tzitzit (Mishna Berura 18, 8)

A cotton blanket is certainly exempt. halacha.co explains

Based on the Gemara, some rishonim claim that the term “garment” in the Torah is reserved for wool and linen, and other materials are only obligated mid'rabanan, while others argue.

Tradition is not to place tzitzis on blankets due to a combination of two exemptions: it is primarily for night use, and it is not worn. Nonetheless the Alter Rebbe rules one should round a corner of a woolen blanket.