Changing the User-Agent and Ethics

The User-Agent is a value set by the client, so it can be changed freely. It's easily set with browser developer tools, extensions, HTTP client libraries, and the like.

Legitimate Uses

• QA that tests rendering across multiple browsers and devices
• Reproducing a specific environment in automated tests
• Setting a UA so that your own crawler honestly identifies itself

Uses to Avoid

• Impersonating a search engine bot to bypass paid content or access restrictions
• Mass scraping while ignoring robots.txt and terms of service
• Disguising identity to evade fees or policies

If You're Building a Crawler

It's good practice to put an identifiable UA and a contact (or an informational URL) in your own crawler. Example: MyBot/1.0 (+https://example.com/bot). This way, a site operator can reach you if a problem arises.

What is technically possible and what is ethically permissible are different things. Changing the UA is a powerful tool, so use it responsibly.