I usually just ask on one of the phone interviews before coming in "Do you guys dress casually or prefer business casual?" and they tell me exactly how they dress. It is that easy.

Blue jeans, a polo shirt and converse or vans are the only thing I've worn to work or an interview since 1999.

I've also interviewed a ton of people and the only time I've noticed what people are wearing are if they were wearing "dress clothes" or they had one of those weird burning man goth cyber warrior outfits on.

"burning man goth cyber warrior outfits"

I think I've just discovered the new office dress code.

I prefer to wear what I normally do. If the company has the same "code over looks" outlook that I have then it won't be an issue. If they object to jeans and tshirt, then we wouldn't have been a good fit anyway. (Of course the exception is client facing roles, there's an understandable reason to dress correctly for that)

"Come, as you are, as you were, .. as a friend".

The safest bet is always chinos and a button-up long-sleeved shirt. Not too casual, not too dressy.

For a while, that is all I owned. It is the most flexible outfit. untucked, sleeves rolled up, top 3 buttons undone and you are chillin on the beach. Button it up, to just top button open, roll down sleeves, you're at work. Tuck it in, add a tie and jacket, and you're ready for a formal occasion. I never quite found the appropriately versatile pair of shoes, however.

Business casual. A tie says "BigCo refugee". A t-shirt and jeans probably won't neg you, but it can in some places.

And remember, you can always ask the HR rep setting up the interview what the typical dress at the company is.

Danger-Will-Robbins. If you're applying at a VC-funded company, there's a decent chance the HR person has no idea what the engineering culture is actually like. Don't wear the tie.

In every company I've worked for (pre-money startups, post-money startups, small public companies, 10000+ behemoths), the HR tech recruiters actually interacted with the team frequently and had a good idea how they dressed and behaved.

I've interviewed with one startup (and got an offer), and I was in business casual (no tie).

Going too casual can hurt you a lot more than too professional, IMHO.