LMK

What does LMK mean?

LMK is "let me know," and it is about as plain as texting shorthand gets. Dictionary.com, Wiktionary, Verizon's parent guide and Greenlight's list of 103 abbreviations all give the same expansion with no second slang meaning. What varies is the job it does in a conversation.

• Asking for an answer later. "lmk if you can come Friday" leaves the question open until the other person knows. This is the core use.
• Asking for an update. "lmk when you get home" or "lmk how the interview goes" means "check in with me after."
• Offering help. "lmk if you need anything" is a standing offer, often sent after bad news. It is kind, though some people find it puts the work of asking back on them.
• Asking for an opinion. "lmk what you think" usually follows a link, a photo or a draft.

The lowercase form, lmk, is far more common in texts than capitals. Either one reads the same.

Other meanings. LMK was also the name of a third-party anonymous-messaging app that plugged into Snapchat. A 2022 article in The Verge, quoted in Dictionary.com's entry, mentions Snap suspending the apps Yolo and LMK. In a headline about app safety, that is what "LMK" refers to.

Examples

• Parent to teen at a sleepover: "have fun, lmk if you want to be picked up early"
• Roommates splitting groceries: "going to Target, lmk if you need anything"
• Friend sharing a playlist: "made this for the road trip, lmk what you think"
• Group project chat: "I'll do the intro slides, lmk which part you want"
• Slack message between coworkers: "draft is in the folder, lmk if the numbers look off"
• After someone's surgery: "thinking of you. lmk if I can drop off dinner"
• Teen to parent, after a game: "practice ran late, I'll lmk when we're leaving"

LMK nearly always comes at the end of a message, after the information or the offer. It can also be used as a verb, as in "I'll lmk," which is a natural way to promise a follow-up.

Where did LMK come from?

• Long before texting: "Let me know" has been an ordinary English request for generations. The abbreviation simply compresses a phrase people already typed constantly.
• Early 2000s: As instant messaging took off, LMK became standard shorthand. An Urban Dictionary definition dates to October 2003, and Dictionary.com lists its origin simply as "from its use in digital communications."
• 2010s: The abbreviation moved from chat windows into everyday texting and comments. Dictionary.com's example sentences include a February 2018 line from The New York Times that ends a request for book recommendations with "LMK."
• 2024 to 2026: Parent-focused guides from Greenlight (updated October 2024) and Verizon (January 2026) list LMK among the basics, alongside staples such as hmu and wyd.

LMK in work messages

LMK has crossed into office chat more completely than most abbreviations. On Slack or Teams, "lmk if you have questions" is routine and nobody blinks. Email is a little different. The more formal the reader, the better it is to write "please let me know." A useful test: if you would not start the email with "hey," spell LMK out.

One more workplace habit worth knowing: "lmk" with a time attached ("lmk by 3") is a polite deadline. It still asks, but it asks for an answer by then.

Is LMK rude?

No. Teachers and parents have nothing to worry about here, and it is safe for school. The closest it gets to rude is tone. A bare "lmk" in reply to a friend's long message about a problem can feel distant, as if the sender is closing the conversation rather than joining it. Adding a real sentence fixes that.

How to reply to LMK

• A friend says "movie at 7, lmk": "I'm in. Can you save me a seat?" or "Can't tonight, next time though."
• Your mom texts "lmk when you're home": "Home now." Short is perfect; the point is the update.
• A coworker writes "lmk if the slides work": "Looks good. One fix on slide 4, otherwise ready to send."

If you need time, "will lmk tonight" is a perfectly good answer to an lmk. It tells the other person you saw the message and when to expect more.

Is LMK still used in 2026?

Yes, and it shows no sign of going anywhere. LMK has outlived dozens of trendier abbreviations because it does a dull, useful job. It no longer feels like slang to most people, sitting closer to "btw" and "asap" than to anything on a Gen Z list. For more texting basics, see the texting abbreviations guide or the printable guide for grandparents.