Hardware acceleration is competing for the graphics card
Input delay and stutter in games whenever Discord is open, with voice working perfectly.
Hardware acceleration means letting a program hand its drawing work to the graphics card instead of the processor. For most apps that's a good trade. For Discord sitting alongside a game, it means two programs asking the same graphics card for time. The game is the one that suffers. It needs a steady stream of frames, and Discord's work arrives in unpredictable bursts.
Discord still works exactly the same; it draws itself using the processor instead.
Fixin Discord open User Settings → Advanced and switch off Hardware Acceleration. It will offer to restart — let it. Test the game again before changing anything else, so you know whether this was it.
NoahNoah shows what Discord is actually taking from the processor and memory while a game runs. You can see whether it's busy enough to be the cause, rather than turning settings off on a hunch.
The game overlay is adding cost to every frame
Constant micro-stutter rather than occasional hitches, in full-screen games specifically.
The overlay is what lets you see messages and who's talking without leaving the game. To draw on top of a game it has to hook into that game's graphics, and that hook runs on every single frame. When it works you barely notice. When it clashes — most often with anti-cheat software, or with a game running truly full screen — you get a steady, even stutter that never settles.
Fixin Discord open User Settings → Game Overlay and switch off Enable in-game overlay. If you want to keep it, turn it off for the one game that stutters instead: same screen, under the per-game list.
Screen sharing is running hot
The PC is fine until you start sharing your screen, then everything slows at once.
Sharing a screen means capturing every frame, compressing it, and uploading it continuously. At 1080p and 60 frames a second that is real, sustained work for the processor and graphics card — comparable to running a second game. No setting makes it free.
Fixwhen you share, drop the stream to 720p and 30fps in the share settings. The difference is barely visible to whoever's watching and it roughly quarters the work. Share a single window rather than the whole screen where you can.
Discord is running when you think it's closed
The PC feels slower generally, and boots slower, even when you haven't opened Discord.
Discord installs itself to start with Windows, and clicking the X closes the window without quitting the program — it keeps running in the system tray, the small icon area by the clock. So it's using memory and checking for updates during every session, including ones where you never used it.
Fixin Discord open User Settings → Windows Settings and switch off Open Discord. To quit it properly, right-click its icon in the system tray → Quit Discord — not the window's X. To see what it's costing meanwhile:
% tasklist /fi "imagename eq Discord.exe"Run in Command Prompt. Lists every running Discord process and its memory use — it is normal for there to be several, but the total should not be large when you are not using it.
Discord is stuck updating in the background
Heavy processor use from Discord that never settles, sometimes with a spinning update screen on launch.
Discord updates itself quietly and often. If an update is interrupted — a connection drop, a sleep at the wrong moment — it can retry in a loop, using the processor continuously without ever showing you an error.
Fixquit Discord fully from the system tray, then reopen it and let the update finish before doing anything else. If it still loops, close it and delete the contents of %AppData%\discord\Cache (paste that into the File Explorer address bar), then start it again.