My xbox series X does not detect my alienware AW2518H monitor correctly

Its the monitor, Nvidia G-Sync monitor's don't play well with Games consoles, pretty much all Nvidia G-Sync monitor's will not go beyond 60hz refresh rate when connected to consoles, it doesn't matter if it's a 120hz / 144hz / 160hz / 240hz / 360hz, you'll be stuck at 60hz

Freesync or Adaptive Sync monitor's are best for consoles to get 120hz,

if your only using a monitor for just console gaming only - Freesync monitor's,

if like me and gaming using PC and console on the same monitor - Adaptive Sync monitor's, ( Freesync and G-sync )

if your only using a monitor for just PC gaming only - Nvidia G-sync monitor's for Nvidia GPU's / Freesync monitor's for AMD GPU's.

Hello, regarding your explanation I will need to try following the steps on this link Advanced video settings for Xbox consoles | Xbox Support. If your issue persists try doing a reset to your console:

Settings > System > Console Info > Reset This Xbox > Reset and Keep my Games and Apps.

Note =>The "Reset and Keep my Games and Apps" option will not cause losing your games, but please be aware that you need to be completely aware of the email address as well as the password of your account before going for it because it will require you to sign in to the account.

With this thing hitting the market (ALIENWARE 34 CURVED QD-OLED GAMING MONITOR - AW3423DW).

Microsoft better get 3440 x 1400 resolution support for the Series X.

Hiya mate yes it’s a 240hz monitor, it’s an Alienware aw2518h. As I said, g sync is off and so is vsync, I noticed the fps cap in apex legends, it caps it at 240 with full screen optimisations disabled and enabled, the game should be smooth at 240fps or uncapped but it isn’t on any game I play, valorant uncapped is horrible so I have to cap just above refresh rate which is smooth but apex uncapped is horrid.

Make sure your monitor supports HDMI 2.0 so it can do 4k at 60hz. HDMI 1.4 can only do 4k at 30hz and the xbox one does not support that. For example, my monitor does not support 4k 60hz with HDMI but it does with display port. My max resolution is 1440p
on HDMI. I do have HDMI 2.0 though, but something must not be detecting it properly.

Monitors are trickier than TVs because auto-detect sometimes does not work correctly and the xbox does not know that the monitor can do 4k at 60hz through HDMI. And if you select Manual from Auto Detect on the xbox one settings, you can't select 4k because
4k is only available when you have auto detect enabled, to my knowledge.

Display port is one thing that monitors like yours have, that support 4k at 60hz and more, but the xbox does not officially support display port and you would need a special "active" adapter for that and xbox can't guarantee that that will work.