Code written during work hours using company resources belongs to the company; personal open‑source projects should be done in your own time and on your own equipment, without mixing them.

No cost involved. When you start a new job, be sure to read the intellectual‑property clauses in your employment contract. The main difficulty is that personal projects and work tasks often share the same computer, so you must keep them separate.

Works produced to fulfill job duties are considered “work‑made‑for‑hire.” Under normal circumstances the author keeps copyright, while the employer has the right to use them for its own business and may not allow third parties to use them in the same way for two years. However, two exceptions exist: works such as software or engineering designs that are created mainly with employer resources and for which the employer bears responsibility, and any works expressly assigned to the employer by contract. In both cases the author retains only the right to be credited. “Employer resources” include hardware, internal networks, and business data. Inventions created while performing job duties or using those same resources are classified as “work‑made‑for‑hire inventions,” with all patent rights belonging to the employer nationwide.

全国人大常委会 (2020). 著作权法（2020 年修正，第十八条）. http://www.npc.gov.cn/npc/c2/c30834/202011/t20201119_308796.html；全国人大常委会 (2020). 专利法（2020 年修正，第六条）. http://www.npc.gov.cn/npc/c2/c30834/202011/t20201119_308800.html

Software is explicitly categorized as “copyright belonging to the employer,” so programmers rarely qualify for the standard rule granting them copyright while the employer retains a two‑year exclusive right to use it. Code written outside work hours can still be deemed a product of employer resources if it is produced on a company computer, accessed company networks, or uses business data. To keep personal projects truly separate, use your own machine, avoid company repositories, and ensure they do not overlap with any company work.