If you have an Nvidia graphics card, you've probably heard of ShadowPlay. It's a feature that you can enable so that when you press a key bind, it saves the last X amount of minutes to a folder on your PC. It's constantly recording using a hardware encoder for a limited hit on your GPU, and it's something that you can't really get on any other hardware. AMD's equivalent is ReLive, but it pales in comparison to ShadowPlay and its performance. However, with OBS, you can make your own ShadowPlay that works on any machine... and yes, it even works on Mac.

How to make your own ShadowPlay replacement with OBS

You need to enable a Replay Buffer

OBS has a feature that you can enable called "Replay Buffer." It does the same thing as ShadowPlay and ReLive, except instead of actively writing temporary recordings to the disk, it stores them in your system memory. You'll need to make sure you have enough RAM, but it's fully configurable and will tell you how much RAM it requires. On my Mac, to record a two-minute replay buffer at 20Mbps, it says that it will only need to hold approximately 288MB of RAM captive.

If you want to set up and configure this feature, it's pretty easy.

1. In OBS, go to Settings
2. Click Output
3. Change Output mode to Advanced
4. Click Enable replay buffer
5. Change the replay time to what you want. I set mine to two minutes.
6. Go to Streaming and set the bitrate to your preference. I have mine at 20000 Kbps.
7. Choose your video encoder. On Nvidia, this should be NVENC, on AMD, this should be AMD HW.
8. Go to the Recording tab and make sure the video encoder says Use stream encoder

You're done! You'll now have OBS set up with a continuous replay buffer. You can change where these are stored in OBS settings, and you can set up instant replays to use a different naming scheme to your other recordings if you want. You'll need to click Start Replay Buffer on the OBS default page, and you can stop it whenever you don't need the replay buffer running.

Next, you'll need to set a key combination to save clips when you need them. In Settings, go to Hotkeys. Scroll down and select Save Replay, and press a key combination that you're comfortable with. You won't have visual feedback when a replay is saved, so you might want to make it easy to be able to save them. That way, you know you didn't accidentally miss it.

The best part about using OBS for this is that you don't need to worry about any kind of computational hit on your hardware, either. It's the same native encoder that you'll get on AMD and Nvidia GPUs, so long as you configure it to use it.