Features

This section describes how to implement common Vercel platform features through the Build Output API through a combination of platform primitives, configuration and helper functions.

The file supports an easier-to-use syntax for routing through properties like , , etc. However, the "routes" property supports a lower-level syntax.

The function from the npm package can be used to convert this higher-level syntax into the lower-level format that is supported by the Build Output API. For example:

The routing feature is a special case because, in addition to the routes generated with the helper function above, it also requires that the static HTML files have their suffix removed.

This can be achieved by utilizing the property in the file:

An Edge Runtime function can act as a "middleware" in the HTTP request lifecycle for a Deployment. Middleware is useful for implementing functionality that may be shared by many URL paths in a Project (e.g. authentication), before passing the request through to the underlying resource (such as a page or asset) at that path.

An Edge Middleware is represented on the file system in the same format as an Edge Function. To use the middleware, add additional rules in the configuration mapping URLs (using the property) to the middleware (using the property).

The following example adds a rule that calls the middleware for any URL that starts with , before continuing to the underlying resource:

When using Prerender Functions, you may want to implement "Draft Mode" which would allow you to bypass the caching aspect of prerender functions. For example, while writing draft blog posts before they are ready to be published.

To implement this, the of the file should be set to a randomized string that you generate at build-time. This string should not be exposed to users / the client-side, except under authenticated circumstances.

To enable "Draft Mode", a cookie with the name needs to be set (i.e. by a Vercel Function) with the value of the . When the Prerender Function endpoint is accessed while the cookie is set, then "Draft Mode" will be activated, bypassing any caching that Vercel would normally provide when not in draft mode.

When using Prerender Functions, you may want to implement "On-Demand Incremental Static Regeneration (ISR)" which would allow you to invalidate the cache at any time.

To implement this, the of the file should be set to a randomized string that you generate at build-time. This string should not be exposed to users / the client-side, except under authenticated circumstances.

To trigger "On-Demand Incremental Static Regeneration (ISR)" and revalidate a path to a Prerender Function, make a or request to that path with a header of . When that Prerender Function endpoint is accessed with this header set, the cache will be revalidated. The next request to that function should return a fresh response.