Merriam-Webster’s Collegiate Dictionary spells LOL (as well as BTW, TMI, and other abbreviations used in text messaging) with capital letters. In a title, the term would appear as follows:

“An LOL Moment”

LOL I Don’t Think So

Merriam-Webster also includes an option to lowercase LOL. If you’re using the lowercase option in your prose, LOL would still be capitalized in your title and in titles you cite, according to the MLA’s guidance on capitalizing titles. However, when the first line of an untitled poem or the full text of a short message stands in place of a title, copy the styling as it appears in the source (MLA Handbook 2.90, 5.29).

“Never thought I’d see the day lol”

“Are we using LOL differently?”

“Enough with the lols, they said”

Note that Merriam-Webster‘s entries for BTW, TMI, and other abbreviations common in text and chat messages do not include a lowercase option. Because stylistic consistency facilitates communication, it’s a good idea to look up all the abbreviations you use in a piece of writing to confirm that the style you apply to one of them can also be used for the others. 

Works Cited

“BTW, Abbr.” Merriam-Webster, 2022, unabridged.merriam-webster.com/collegiate/BTW.

“LOL, Abbr.” Merriam-Webster, 2022, unabridged.merriam-webster.com/collegiate/LOL.

MLA Handbook. 9th ed., Modern Language Association of America, 2021.

“TMI, Abbr.” Merriam-Webster, 2022, unabridged.merriam-webster.com/collegiate/TMI.