Just noticed horizontal cracks on two of my front teeth at the top

[Itisnotdownonanymap]

No pain, but if I run my finger nail over them then I can feel quite it quite clearly. Literally just noticed while I was brushing my teeth this morning.

Obviously I'll make a dental appointment, but what could it be and how urgent is it?

I have vertical lines/cracks on mine. Also no pain. Apparently it’s an age thing and nothing to worry about. Not sure if horizontal could be the same?

Common, possibly always been there and you've only just noticed, craze cracks in enamel are normal. Also common in those with fluorisis or hypoplastic enamel. Surface cracks in enamel are normally benign provided they don't extend into dentine. Get them looked at but chances they're harmless.