What is mdnsd and why is it killing my battery?

This is a DNS daemon, and may see heavy use from a really wide variety of apps.  

Anything that's constantly hitting URLs, such as a social media app(s), or other apps that update frequently, could see high use from this.

If it were me, I'd diagnose by first disabling most of my background apps, except core (phone, built-in texting app, maybe email), and see if this fixes it.

If so, start by adding back in background apps, but give each 1-2 a day or so to run, before adding more.

One way to do a "quick check" here is to enable data-saver, and see if this also brings down the usage (this should, in thoery, prevent almost all non-essential background apps from doing things that require a DNS check).

Just did factory reset (full refresh, with no app/data transfer), and the process is still there (just as the unnamed process). I checked my friends' phones and they do not seem to have this listed in the battery usage screen. What's going on there? Is this an LG or AT&T issue? I suspect it's related to some of the bloatware apps, but can't figure which one. I'm currently running the OS with no additional apps installed (Facebook is the only add-on app).

I also have determined that Facebook is the culprit for my MDNSD issue on my S5.  I've noticed that if I open Facebook and I get the header but no actual body to my newsfeed, then every single time this happens I can check setting and see that MDNSD is there at the top of the list, starting to hog up all resources.  If I reboot while on the charger/QI and leave it plugged in for stew minutes afterward, it clears it up (until the next flakey Facebook launch).  If I do a reboot while not on the charger or if I immediately take it off the charger, it is still there.

I'm running the latest version of Facebook (as of this date) but finding anyone with this same issue seems pretty difficult in my search (which is how I ended up here).

Thank you, pgrey. After the rebuild, I pretty much left everything as is and the process appeared but with not as high percentage. I'm wondering if this is caused by the bloatware that comes with LG G3 that I cannot uninstall (do I really need the Uber on my phone if I have no intention of using it in near future? ot Twitter app?). Anyway, Facebook/Messenger is the app that use most and it's probably the one that causes the problem (other than Facebook, I have Feedly, Player FM and All-in-one Remote, but I do not think these would cause the problem). It looks like the Facebook messenger is even worse than Facebook, since after installing it, the process takes a lot more power; and unfortunately, without it, I cannot access messages, but I'll probably leave without the messaging capability for a while to see if it helps).

I'm having the same problem and have tried deleting Firefox, Facebook, Messenger, and disable Chrome, and yet the process persists. I'm losing hope at this point.

I uninstalled Facebook Messenger and noticed that the MDNSD power usage went down. I tried then to use the Facebook on the mobile site and making sure it worked fine, I uninstalled Facebook completely and the process seems to have disappeared. I think I also noticed improved battery usage. Will continue monitoring it, but there seems to be hope.

Yeah @alekdavis, that's sort of the nature of social-media apps, they're going to be really data-intensive, particularly depending on if you have a small refresh-window setting(s).  You can change this, which would probably help some, but ultimately the browser is going to be more efficient, at least with the current implementations.

I suspect that eventually things like FB mobile will become more flexible, allow you to choose who you get more frequent updates from, and how they receive notifications.  It's a tricky business, people want their latest updates, and security/reliability (hence a lot of DNS refreshes), but they also don't want to sacrifice battery.

You can sort of have two, frequent/accurate-safe/low-battery, choose two (no, not entirely scientific, but not a bad rule-of-thumb, not just for social-media apps) ;-]

After a couple of days of not using the Facebook apps, it seems like I got a new phone. The battery life has improved drammatically. There is no MDNSD process in the battery usage. I'm so happy. The mobile Facebook web app works very similar to the app, except you cannot edit comments (I haven't tried uploading or posting so can't say how it works). I installed the Swipe app (from Google play), which is a lightweight Facebook mobile app wrapper. There are some bugs, but it allows me to read and post messages. Anyway, hope this helps someone.

It's caused by the Facebook app, specifically the nearby friends feature. Uninstall FB, reboot phone, reinstall, but do NOT turn nearby fridnds back on. Problem solved! Hooray!

It's caused by the Facebook app, specifically the "nearby friends" feature. Uninstall FB, reboot phone, reinstall, but do NOT turn the nearby friends feature back on. Problem solved! Hooray!

I didn't use the nearby friends feature either.