Files typically open in a new browser tab rather than downloading because the web server specifies a MIME type indicating the file is directly displayable by the browser. Common viewable formats include PDFs, images, and certain text files. This behavior differs from downloading, which occurs when the file type isn't natively renderable by the browser or when the server sends a specific header (Content-Disposition: attachment) forcing a download.

For example, clicking a link to a PDF report hosted on a company website often displays it within a new browser tab using the browser's built-in PDF viewer or a plugin like Adobe Reader. Similarly, opening an image file from a photo-sharing platform like Flickr typically renders the image directly in the tab. Web-based document viewers, like Google Docs, also commonly employ this tab-opening method.

This behavior provides immediate preview convenience without cluttering the downloads folder. However, limitations include potential browser plugin dependency for some formats and slower loading for very large files. Opening files directly presents security considerations, as malicious files disguised as viewable content could exploit browser vulnerabilities. Browser settings allow users to override this behavior, choosing to download certain file types instead. Future web standards continue to evolve finer control over file handling.