Archer C9(US) V1 180125 is only used for US region.
If your current firmware is Archer C9 (UN), you can't update with US version because of FCC and CE.

I'll say, when I first bought my v1 US version, somehow I upgraded to the UN 4.x version. It's MUCH better than the US 3.x; however, my Chromecast/other Google Cast devices didn't work properly with it, so I've been on the latest US version from Feb since.So, I did successfully downgrade. That said, it probably wouldn't be covered it it bricked your device doing so.

http://forum.tp-link.com/showthread.php?98986-Archer-c9-V1-Firmware-3.17.0-unable-to-flash-firmware-Never-uploads-firmware
I used above transition firmware to flash 180125 US to 160517 UN.
Because of 180125 US firmware for KRACK's vulnerability, google TV provided by LGUplus in South Korea, channel up/down picture freeze.

i upgraded to archer_c9v1_us-up-ver3-17-1-P1[20180125-rel56387] and i lost my white/black list ability for devices so i could no longer limit my kids devices to specific times of the day

tp-link sent me a new firmware c9v1_un-up-ver4-1-0-P12002[20180223-rel35954] the white/black list was back but i lost my internet, the UI send it was connected had IP etc but could not get out to any site so i have reverted back to the first one. i wish i could go back to the 2016 version but i am afraid to try

dice12345 wrote

. i wish i could go back to the 2016 version but i am afraid to try

It's just a router. It'll cost about $100 to replace if you brick it. This is not your first router so you probably have a old spare sitting in a drawer somewhere. There is nothing to fear except having to use an old router while you wait for a new one to be delivered by amazon if disaster strikes. It's not like you are changing firmware on your $65,000 BMW. Go ahead and flash your router. If it explodes, buy a new and better router maybe something not from tp-link.

Or you could load DD-WRT but there goes the warranty. I have an old Linksys router that I loaded DD-WRT and it worked great. Only issue was it was a 'G' so it was slow and did not support 'N' or 'AC'. I keep the old linksys around as a backup in vase my C8 dies. https://www.dd-wrt.com/wiki/index.php/Supported_Devices#TP-Link

No update available for europe, is there a reason for this, or is it a lack of understanding customer retention aka VW.

@Kevin SG: Thanks for your reply. My router is US version. I upgraded it with a UN version because TP-Link suppport instructed me to. @onfire4g05: Thanks for your reply. I didn't realize until you said it that the US version is 3.x instead of 4.x version. That's weird and I wonder why is it so. @jinheumna & @dice12345: Is c9v1_un-up-ver4-1-0-P12002[20180223-rel35954] a Beta version or a final one? I didn't find it published on Archer C9 support page. Regarding the last point, looking for the firmware above, I did find something really interesting in Archer C9 firmware for Canada users. If you look there (at https://www.tp-link.com/ca/download/Archer-C9_V1.html#Firmware), TP-Link offers 3 firmwares: - The one I'm currently using, Archer C9(UN)_V1_160517 - An update to that one from a few months later, Archer C9(US)_V1_161008, and - (drumroll) the one I was asking for, Archer C9(US)_V1_180125 So, now I'm quiet positive that is ok to upgrade. On the other hand, maybe I should contact TP-Link to know what fixes c9v1_un-up-ver4-1-0-P12002[20180223-rel35954] contains (KRACK?) because I prefer 4.x to 3.x. Thank you all for your feedback, and I will post again once I decide and upgrade.