The letters "LMK" spelled out in blocks.
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Has someone ever asked you to “lmk?” Here’s what this common internet acronym means and how to use it.

Let Me Know

LMK stands for “Let me know.” This initialism is used to tell someone that they should inform you of something in the future. For example, you could tell someone who is currently sick to “LMK if your fever goes down” or “LMK if you need anything.”

The acronym often implies that another conversation will take place in the future, likely when the other person replies. It is mostly used in texts and emails instead of real-life conversations. When speaking to someone IRL, it’s best to use the full phrase “Let me know.” You can use this acronym in both the uppercase LMK and the lowercase lmk, as both are equally common.

The phrase “Let me know” also tends to make a line of questioning less confrontational and more casual. Instead of sounding like you’re directly asking someone, LMK tends to sound more friendly. Therefore, it can be used for potentially tense or difficult conversations with other people.

A Brief History of LMK

Before becoming an internet acronym, the phrase “Let me know” was already extremely widespread in English. It is versatile and applies to various contexts, from a restaurant server asking a patron whether they need anything to asking someone what time a meeting is going to be held.

Its shortened version originated from early internet chatrooms, forums, and message boards in the 1990s, where it became popular alongside other internet acronyms. On the internet-slang website Urban Dictionary, the earliest available definition for LMK is from 2003. It simply reads, “Let me know.”

It has seen growing use in the 2000s and beyond, especially with the rise of SMS, instant messaging, and direct messaging. It’s very common to use LMK in personal conversations with other people.

Asking for an Answer

A couple standing back-to-back while texting.
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There are two main reasons to use LMK in a sentence: so that you can ask someone a question, or request additional information in the future.

In the first case, you use LMK to ask questions and expect an answer from the other person at the soonest possible time. This is commonly done when messaging someone who is currently offline, or when sending a message through a channel where someone doesn’t need to reply immediately, like email or SMS. For example, you’d say, “LMK if you’re free tomorrow.”

You could also say “LMK” in addition to another question, such as “LMK what you think” or “LMK where you are.” Using LMK can make your message seem less abrupt and rude and more casual and non-confrontational.

LMK to Ask for Updates

Another reason to use LMK is to ask for future updates from someone on a particular situation. In this scenario, “lmk” is often paired with phrases like “what happens” or “how it goes,” which is pointing to a certain upcoming event.

For example, let’s say that one of your friends is about to have an important job interview. Your text to them might read “Good luck, and lmk how it goes!” This implies that you want them to update you on the interview later.

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How to Use LMK

LMK and the phrase “Let me know” are essentially interchangeable so that you can switch between the two. While most acronyms tend to be used strictly for casual conversations, LMK is versatile enough to be acceptable in professional settings. It is not uncommon to use LMK in an email asking for feedback or insights from other people in the workplace.

Here are a few examples of LMK being used:

  • “I just sent you the second revision of the design. LMK what you think of it.”
  • “Hey, I heard you have a game tomorrow night. LMK what happens.”
  • “lmk where you are. I’m going to pick you up.”
  • “Can you babysit for me on Friday night? lmk, thanks.”

If you want to expand your online slang vocabulary even further, you should look into our articles about WYD, TTYL, and HBU.

RELATED: What Does "HBU" Mean, and How Do You Use It?

Profile Photo for Vann Vicente Vann Vicente
Vann Vicente has been a technology writer for four years, with a focus on explainers geared towards average consumers. He also works as a digital marketer for a regional e-commerce website. He's invested in internet culture, social media, and how people interact with the web.
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