Splices in electrical wiring should be made:

Making splices in electrical wiring inside a box is essential for several reasons related to safety, accessibility, and code compliance. When splices are made inside a box, they are protected from damage and moisture, which can occur if they are exposed. Additionally, electrical boxes allow for easier access in the future if repairs or changes are needed, ensuring that electricians can work safely without having to disturb the wiring significantly.

Electrical codes typically require that splices be contained within a junction box to make sure that they are securely housed, provide proper mechanical protection, and enhance safety by minimizing the risk of electrical shock or fire due to exposed connections. This practice also helps with proper ventilation and heat dissipation, reducing the potential for overheating at the splice point.

Using solder-less connectors or electrical tape alone does not provide the necessary protection and reliability that a junction box does. While these methods can be part of the splicing process, they should only be used as part of a full installation that includes proper enclosure in a box. Making splices outside of a box exposes them to elements and potential hazards, making it an unsafe and non-compliant practice.