Each game has their own rules about this. So you should check that game's rules.
Although, you could press the Submit run button, and scroll down the page to see if you can check the emulator switch or not. Or to see if it says that emulators are banned.
I didn't read the part about the website, but what I said is still true. Oops lol
@Poolroom37 do you mean that there's an emulator on a website, or that you're using an emulator to emulate a website?
Also what game is this for? And I would still ask the game moderator(s)
@YUMmy_Bacon5 I mean there is a Super Mario Bros. 3 emulator on the website,and I wanted to ask if using this emulator is legal
Then you need to look at the rules on the Super Mario Bros. 3 page and if it's not clear, ask in their forums or their discord to clarify. As mentioned before though, most games will not allow a browser-run emulator, but this is why checking the rules for specific games/asking said community is important because you never know.
I agree, ask in SMB3's Discord server or forums, and provide the link of the site that you're using to them.
Also reading the game's rules would be good. Although, there isn't really an allowed list of emulators there.
And downloading an actual emulator would be better, rather than using one on the web.