[jokethrowaway]

It's pretty common to have penalties if you quit without notice. It's also a breach of contract. Employers probably won't go after you in court though, unless your immediate departure cause them some damage larger than the lawyer's bill.

One month is common for juniors or contractors. I've never seen a contract with less than 1 month notice in tech. Three months is common for senior or management positions.

[Aeolun]

I’ve only ever seen one month in both Europe and Japan. With no stipulated penalties for leaving immediately (beyond, you know, being an a*).