I read somewhere that a full 50% of the people on dating sites are married. Without even Googling it, I believe it.   I'm including not only fully married people who are out to cheat, but the recently separated who have one foot in the marriage counselor's office and the other foot in a dating site. How to spot a married person on a dating site?....Well when you see "Separated" as their status, it should make you take pause before proceeding.  Many times this is more about what they want rather than what actually is.  Or it's just a flat out lie.

Some other clues:
1.  Short, brief profile essays that don't say much about anything.
2.  No photo, or...
3. Profile photos that are either really old.  No close ups.  Lots of sunglasses and baseball caps.
4. Not easily accessible after initial connection:
 a. You call them and it rings and rings and goes to voicemail.
 b. Or they answer and it sounds like they are standing outside in the backyard or a parking lot.  That's because they are.
c. They call you at odd times outside of normal downtime from work.
d. They don't invite you to their house, it's always your place or a public place.
e.  They don't introduce you to any of their friends, or if they do, it's usually their wingman who's in on the secret.

If your gut is telling you this new person is married, always listen to your gut and then take the risk (because it's ALL risk) and ask if they are married.  Most of the time they will 'fess up because their guilt is eating them up.

Then of course you're going to hear all about how the marriage has been over for years.  They just drifted apart, or else the other spouse is cheating, too and blah....blah...blah.  If all you're after is a jaunt without  pajamas, then it really doesn't matter.  But if you're seriously searching, then dump them quickly and move on.

"51% of all online dating people are in a relationship, only 21% are really single and 11% are married."
PairedLife.com, January 2017