If you're a non-resident of California who never physically works inside California, then your W-2 salary or wages are not subject to California taxes.
But if you're an independent contractor (your earnings are reported on a 1099-NEC or a 1099-MISC instead of a W-2) who performs services for a client located in California, your income may be subject to California taxation.
**Answers are correct to the best of my ability but do not constitute tax or legal advice.