tryfiles

try_files is an Nginx directive that specifies an ordered list of files or URIs to check for existence. Nginx tests each item in order and serves the first one that exists, effectively enabling a controlled fallback sequence. If none of the listed files or URIs exist, Nginx can rewrite the request to a final URI, enabling patterns such as a front controller for web applications or a custom error path.

Syntax and parameters: the directive takes one or more path expressions, which can be absolute file paths, or variables that expand to paths. An optional final URI can follow the list, beginning with an equals sign (=) to indicate an exact internal redirect. For example, try_files $uri $uri/ /index.php?$query_string tells Nginx to serve the requested file if it exists, or the requested directory, and if neither exists, to internally redirect to /index.php with the original query string.

Behavior and mechanism: on each request, Nginx expands the arguments and checks for the presence of corresponding files or directories on disk. The first existing item is served according to the active location context. If none exist and a final URI is provided, Nginx performs an internal redirect to that URI. If the final parameter begins with =, it forces an exact internal redirect to that URI. Without a final parameter, a failure to match any item typically results in a 404 error.

Common usage: try_files is widely used to implement clean URLs with a front controller (for example, PHP front-ends) and to provide graceful fallbacks for static assets in single-page applications. It is often combined with PHP fastCGI processing or other handlers in a location block.

Limitations and considerations: the directive relies on filesystem state and path resolution, so care is needed with variables and aliases. Performance is generally efficient, but each request may involve multiple existence checks.