Yes, it is possible to get fired from your job for posting adult-related content online, even if you are over 18. Whether your boss has the right to fire you for things you do in your private life depends on several factors, including your employment contract, company policies, local laws, and the nature of the content.

Here are some key considerations:

1. Employment Contract and Company Policies: Many employers include clauses in employment contracts or handbooks that address behavior outside of work, especially if it could affect the company’s reputation. If your online activity violates these policies, your employer may have grounds to terminate your employment.
2. Impact on the Company’s Reputation: If your online activity is linked to your employer or becomes public in a way that harms the company’s reputation, your employer may take action. This is especially true if your job involves a public-facing role or if your behavior conflicts with the company’s values.
3. At-Will Employment: In many places, such as most U.S. states, employment is “at-will,” meaning an employer can terminate your employment for any reason, as long as it is not discriminatory or in violation of specific laws. This could include actions in your private life that the employer deems detrimental to the business.
4. Local Laws and Protections: Some jurisdictions have laws that protect employees from being fired for legal activities conducted in their private time. However, these protections vary widely, and posting adult content may not always be covered, especially if it conflicts with company policies or harms the employer’s interests.
5. Industry Standards: Certain industries, such as education, healthcare, or roles involving minors, may have stricter standards regarding employee behavior, both online and offline. Posting adult content could be seen as incompatible with these standards.

In summary, while you have a right to privacy and freedom of expression, your employer may still have the right to fire you if your online activities conflict with company policies, harm their reputation, or violate industry standards. It’s important to review your employment contract and company policies, and consider the potential consequences of your online behavior. If you’re unsure, consulting with a legal professional in your jurisdiction can provide clarity.