Builders Overview

Builders are modules that transform your source code into the outputs, being either static files and/or lambdas, which are served by our CDN at the edge.

When to Use Builders

If your project has source files that require transformation to be served to users, Builders enable this ability when deploying.

Whether HTML files need to be minified, or dynamic content such as a Node, PHP, or Go app, need to be deployed, Builders offer the flexibility and availability needed to reach that goal.

How to Use Builders

Builders can be used with Now by creating a now.json file in a project and then using a builds property within that configuration:

  "builds": [
    { "src": "*.html", "use": "@now/static" },
    { "src": "date.js", "use": "@now/node" }

The builds property is an array of objects where each object is a build step, including a src and a use property, at least.

The Builder will receive a list of files based on the src property's glob value.

Developing your Own Builder

Extending the feature-set of a Now deployment is as simple as creating a Builder that, as previously mentioned, takes a list of files and outputs either static files or dynamic Lambdas.

A full API reference is available to help with creating Builders.

Technical Details

Caching Data

A builder can retain an archive of up to 100mb of the filesystem at build time. The cache key is generated as a combination of:

  • Deployment name (i.e., the app name)
  • Team id or user id
  • Entrypoint path (e.g., api/users/index.go)
  • Builder identifier including version (e.g.: @now/go@0.0.1)

The cache will be invalidated if any of those items changes. The user can bypass the cache by running now -f.


  • Builders can run for a maximum of 15 minutes before the execution times out.
  • The maximum cache archive size of a Builder is 100mb.
  • The cache TTL is 7 days.
  • Default lambda bundled output size is 5mb, however, configurable.

Configuring Lambda Bundle Size

Each lambda output, by default, has a bundle size limit of 5mb to help keep cold boot times low, but can be configured up to 50mb with the maxLambdaSize config option.

The lambda threshold can also be defined by the builder that outputs the lambda (for example, @now/go, by default, is 15mb), but the user configuration takes precedence.

  "builds": [
    { "src": "*.go", "use": "@now/go", "config": { "maxLambdaSize": "20mb" } }

Using the @now/go Builder and configuring the maxLambdaSize within a now.json configuration file.