User-Agent Parser

A user-agent parser turns a browser's user-agent string into hints about the client, such as browser family, operating system, device class, and rendering engine. These strings are historical compatibility signals, not a reliable identity mechanism. Modern browsers may reduce or freeze values, and different products can send the same token sequence. Parse the string to debug behavior, not to make security decisions.

Compare the raw value with the behavior you are investigating and record the request date, platform, and feature support separately. Be cautious with bots, embedded webviews, privacy browsers, and spoofed strings. Prefer capability detection and explicit client hints when implementing a product decision. If a parser returns an unknown value, keep the raw string for diagnosis instead of silently assigning a precise browser or device identity.

A developer may need to inspect a captured string from a log or bug report without sending it to another service. Local parsing is immediate and makes the privacy boundary obvious. It does not eliminate the privacy implications of the original request: user-agent values can contribute to fingerprinting. Collect only what your product needs, avoid brittle browser-specific branches, and test feature support directly whenever possible.