If you suspect your signifigant other might be using a dating site or app, there are a few ways to confirm your suspicions, including through starting your own infidelity investigation.You'll need to check their phone for common dating apps, conduct a Google search using personal details like their email address and, if necesary, create test accounts on popular apps and sites to see if your signifigant other is returned as a potential match.If all else fails, you can hire a professional investigator to find out for certain whether your signifigant other is using a dating site.The first step is to be aware of common dating sites and apps (many of which are intended to look inconspicuous) so that if you stumble upon them on a shared devices's apps or browsing history, you’ll recognize them.Many sites and apps (like Tinder) only allow people to see each other based on location and mutually matching search criteria (like age and sex).
This helps keep your public identity somewhat disguised.
For dating sites, it can be a little more complicated.
You can always scan through emails to see if any raise a red flag (for example, Match.com), as these websites typically send a welcome email and occasional updates.
Ultimately, if you’re worried that your significant other is on a dating site, there are many options for sleuthing (ranging from a quick scan through emails and browser history to more intensive—and expensive—actions).
If nothing else works (or you don't have the time to conduct an exhaustive search that may or may not be conclusive), consider hiring a private invesitgator.