What to wear to a job interview when you cannot ask what the dress code is

The advice everywhere is to dress one level above the role. That is not wrong, but it is hard to act on when you have never seen the office and the recruiter told you the team is pretty relaxed.
Work out the real dress code first
This usually takes ten minutes. Look at the company careers page, any recent team photos, and how people who already hold your job dress in their profile pictures. If the whole engineering team lives in hoodies and you arrive in a three piece suit, you have mostly signalled that you did not look.
If you still cannot tell, ask. Messaging the recruiter to ask what people normally wear is not a strange question, and nobody has lost an offer over it.
One step above, not three
For most offices that means dark trousers or unfaded jeans, a plain shirt or a fine knit, and shoes that are not trainers. For a client facing or finance role, add the jacket. For a workshop or a kitchen, dressing up too far is its own mistake.
Fit does more than price
A cheap jacket that fits reads better across a table than an expensive one that does not. Shoulders are the part a tailor cannot easily change, so buy for the shoulders and have the sleeves and waist taken in. If the interview is remote, everything above your elbows is the whole outfit.
Video interviews
On a call, the outfit is everything from the chest up, plus whatever the camera sees when you lean forward. A plain shirt, knit or blouse in a mid tone works better than white, which blows out on most webcams, or a fine stripe, which shimmers. Dress the bottom half too; you will stand up at some point, and it changes how you sit.
Check the background is plain and the light is in front of you, not behind. Those two things do more for how you come across than anything you are wearing.
Second interviews and the day you start
By the second round you have seen the office, so dress like the people in it, one small step up. The first day is the same rule again. Nobody is trying to catch you out on either; they want to see that you looked.
Build it from what you own
Most people already have an interview outfit in their wardrobe, sitting in three separate places. The hard part is remembering what is in there. Photograph your clothes once, ask for something for the occasion, and you tend to find combinations you had forgotten.
You can try the detection part on this site without installing anything. Upload a photo of an outfit and it pulls out the individual pieces.
Questions people ask
Should I wear a suit to a job interview?
Only if the people who already do the job wear one. For most offices, dark trousers or unfaded jeans, a plain shirt or fine knit and shoes that are not trainers is one step above the room, which is the right amount. Add a jacket for client-facing or finance roles.
What should I wear to a video interview?
A plain top in a mid tone, a plain background and light in front of you. Avoid white, which blows out on camera, and fine stripes, which shimmer. Dress the bottom half too, because you will stand up.
Is it better to be overdressed or underdressed for an interview?
Slightly over. One step above the room shows you looked; three steps above shows you did not. If you cannot find out what people wear, ask the recruiter; it is a normal question.