I speedrun a flash game and I need video for it. My pc is too slow to handle chrome, obs, and livesplit at once to work at good performance. I decided to not use livesplit to speed it up a little, and time it later. It is still lagging. Are there any ways to speed up a flash game (i use google chrome)

I'm not sure about what game you're playing, but artificially speeding up the game will almost always be banned. You can't just artificially speed up a game to reduce lag, that won't create an even playing field for all the runners unless everyone is doing the same thing. You would need to contact the community and/or the mods of the game in question to get a more definitive answer on the legality of something like that.

Unfortunately, the downside with running PC games (or games that run in browsers) is that if your computer can't handle everything running at once, then it sounds like it's time for a computer upgrade. Alternatively, you could try to lower your OBS settings and use a lower resolution or a lower bitrate to see if that frees up resources for your computer to hopefully prevent the game from lagging.

One thing you could try, is to use the "Bluemaxima Flashpoint" project (a project dedicated to preserve old flash games due to the incoming stop for browser flash support, downloaded from https://bluemaxima.org/flashpoint/ ), which runs the game locally on your computer through flash.

This has the potential to reduce game lag, even for stronger computers. For example, we recently found out that all the flash games in Robot Wants series work much better while running locally, than playing them on the browser, and we aren't going back.

I'm not sure if your computer will handle the games differently that way, with OBS and Livesplit working at the same time, but it may be worth a try.

You should however, check with the game mods/community if that is allowed. The flashpoint program takes the games versions from specific sites (like Armor Games, Newgrounds, Kongregate, etc), and sometimes the versions are different between different sites.

But as @Timmiluvs said, if your computer can't handle browser games then it is probable time for an upgrade.

Edit: You can also try playing on a different browser. I found for myself that Google Chrome is sometimes not the best when it comes to handling CPU usage. I personally use Firefox or Pale Moon browsers for speedrunning browser games not in flash, and for flash games the mentioned flashpoint program.

Agreed with all the above. Keep in mind that the more tabs you have open in your browser, the more memory used and the slower the game will run. As a moderator for some flash games, there should be no issue using BlueMaxima's Flashpoint if desired, though always check the rules for your specific game.

Make sure to adjust your recording settings to lessen the strain on your computer and close every program non-essential to your speedrun.