Most places I've been at don't have much room to negotiate salary. You can often get a better vacation package though if you ask.

The first time I tried to negotiate (2006) I asked for $52k from $50k and they told me no.

The next time (2008), offer was $60k, I countered at $100k (job required relocation) and we met at $80k.

The next time (2011), offer was $110k, got $120k (relo again, this time to a tech center)

Next time (2012), offer was $125k, got $140k and more equity.

I’ve never had a job offer rescinded over it which was always something I heard about growing up.

Of course times change and ymmv.

This might be true at large companies where you're being handled by a HR team.

Smaller companies are typically very willing to negotiate. It can't hurt to ask for 20% more. The worst that will happen is they'll say no.

Asking for more than 20% gets a bit risky.

Large companies also often have a lot of room to negotiate.

Right, but often not salary. You can get a hiring bonus or more vacation time. What each company can give is different, and it changes with time.

That has worked for me precisely never; in fact I gave up negotiating over job offers at all because what I always wanted was more time off, and all I got was "sorry, we only distribute vacation time based on seniority".