Build Output Configuration
.vercel/output/config.json
Schema (as TypeScript):
Config Types:
The file contains configuration information and metadata for a Deployment. The individual properties are described in greater detail in the sub-sections below.
At a minimum, a file with a property is required.
.vercel/output/config.json
The property indicates which version of the Build Output API has been implemented. The version described in this document is version .
.vercel/output/config.json
The property describes the routing rules that will be applied to the Deployment. It uses the same syntax as the property of the file.
Routes may be used to point certain URL paths to others on your Deployment, attach response headers to paths, and various other routing-related use-cases.
| Key | Type | Required | Description |
|---|---|---|---|
| src | String | Yes | A PCRE-compatible regular expression that matches each incoming pathname (excluding querystring). |
| dest | String | No | A destination pathname or full URL, including querystring, with the ability to embed capture groups as $1, $2, or named capture value $name. |
| headers | Map | No | A set of headers to apply for responses. |
| methods | String[] | No | A set of HTTP method types. If no method is provided, requests with any HTTP method will be a candidate for the route. |
| continue | Boolean | No | A boolean to change matching behavior. If true, routing will continue even when the src is matched. |
| caseSensitive | Boolean | No | Specifies whether or not the route should match with case sensitivity. |
| check | Boolean | No | If , the route triggers and |
| status | Number | No | A status code to respond with. Can be used in tandem with Location: header to implement redirects. |
| has | HasField | No | Conditions of the HTTP request that must exist to apply the route. |
| missing | HasField | No | Conditions of the HTTP request that must NOT exist to match the route. |
| locale | Locale | No | Conditions of the Locale of the requester that will redirect the browser to different routes. |
| middlewareRawSrc | String[] | No | A list containing the original routes used to generate the . |
| middlewarePath | String | No | Path to an Edge Runtime function that should be invoked as middleware. |
| mitigate | Mitigate | No | A mitigation action to apply to the route. |
| transforms | Transform[] | No | A list of transforms to apply to the route. |
Source route:
| Key | Type | Required | Description |
|---|---|---|---|
| eq | String | Number | No | Value must equal this exact value. |
| neq | String | No | Value must not equal this value. |
| inc | String[] | No | Value must be included in this array. |
| ninc | String[] | No | Value must not be included in this array. |
| pre | String | No | Value must start with this prefix. |
| suf | String | No | Value must end with this suffix. |
| re | String | No | Value must match this regular expression. |
| gt | Number | No | Value must be greater than this number. |
| gte | Number | No | Value must be greater than or equal to this number. |
| lt | Number | No | Value must be less than this number. |
| lte | Number | No | Value must be less than or equal to this number. |
Source route:
| Key | Type | Required | Description |
|---|---|---|---|
| type | "host" | "header" | "cookie" | "query" | Yes | Determines the HasField type. |
| key | String | No* | Required for header, cookie, and query types. The key to match against. |
| value | String | MatchableValue | No | The value to match against using string or MatchableValue conditions. |
Source route:
| Key | Type | Required | Description |
|---|---|---|---|
| redirect | Map | Yes | An object of keys that represent locales to check for (, , etc.) that map to routes to redirect to (, , etc.). |
| cookie | String | No | Cookie name that can override the Accept-Language header for determining the current locale. |
Source route:
| Key | Type | Required | Description |
|---|---|---|---|
| action | "challenge" | "deny" | Yes | The action to take when the route is matched. |
Source route:
| Key | Type | Required | Description |
|---|---|---|---|
| type | "request.headers" | "response.headers" | "request.query" | Yes | The type of transform to apply. |
| op | "append" | "set" | "delete" | Yes | The operation to perform on the target. |
| target | Yes | The target of the transform. Regular expression matching is not supported. | |
| args | String | String[] | No | The arguments to pass to the transform. |
The routing system has multiple phases. The value indicates the start of a phase. All following routes are only checked in that phase.
| Key | Type | Required | Description |
|---|---|---|---|
| handle | HandleValue | Yes | The phase of routing when all subsequent routes should apply. |
| src | String | No | A PCRE-compatible regular expression that matches each incoming pathname (excluding querystring). |
| dest | String | No | A destination pathname or full URL, including querystring, with the ability to embed capture groups as $1, $2. |
| status | String | No | A status code to respond with. Can be used in tandem with header to implement redirects. |
The following example shows a routing rule that will cause the path to perform an HTTP redirect to an external URL:
.vercel/output/config.json
The property defines the behavior of Vercel's native Image Optimization API, which allows on-demand optimization of images at runtime.
| Key | Type | Required | Description |
|---|---|---|---|
| sizes | Number[] | Yes | Allowed image widths. |
| domains | String[] | Yes | Allowed external domains that can use Image Optimization. Leave empty for only allowing the deployment domain to use Image Optimization. |
| remotePatterns | RemotePattern[] | No | Allowed external patterns that can use Image Optimization. Similar to but provides more control with RegExp. |
| localPatterns | LocalPattern[] | No | Allowed local patterns that can use Image Optimization. Leave undefined to allow all or use empty array to deny all. |
| qualities | Number[] | No | Allowed image qualities. Leave undefined to allow all possibilities, 1 to 100. |
| minimumCacheTTL | Number | No | Cache duration (in seconds) for the optimized images. |
| formats | ImageFormat[] | No | Supported output image formats |
| dangerouslyAllowSVG | Boolean | No | Allow SVG input image URLs. This is disabled by default for security purposes. |
| contentSecurityPolicy | String | No | Change the Content Security Policy of the optimized images. |
| contentDispositionType | String | No | Specifies the value of the response header. |
The following example shows an image optimization configuration that specifies allowed image size dimensions, external domains, caching lifetime and file formats:
When the property is defined, the Image Optimization API will be available by visiting the path. When the property is undefined, visiting the path will respond with 404 Not Found.
The API accepts the following query string parameters:
| Key | Type | Required | Example | Description |
|---|---|---|---|---|
| url | String | Yes | The URL of the source image that should be optimized. Absolute URLs must match a pattern defined in the configuration. | |
| w | Integer | Yes | The width (in pixels) that the source image should be resized to. Must match a value defined in the configuration. | |
| q | Integer | Yes | The quality that the source image should be reduced to. Must be between 1 (lowest quality) to 100 (highest quality). |
.vercel/output/config.json
The property relates to Vercel's Internationalization feature. The way it works is the domain names listed in this array are mapped to the routing variable, which can be referenced by the configuration.
Each of the domain names specified in the configuration will need to be assigned as Production Domains in the Project Settings.
Objects contained within the configuration support the following properties:
| Key | Type | Required | Description |
|---|---|---|---|
| domain | String | Yes | The domain name to match for this wildcard configuration. |
| value | String | Yes | The value of the match that will be available for to utilize. |
The following example shows a wildcard configuration where the matching domain name will be served the localized version of the blog post HTML file:
.vercel/output/config.json
The property allows for overriding the output of one or more static files contained within the directory.
The main use-cases are to override the header that will be served for a static file, and/or to serve a static file in the Vercel Deployment from a different URL path than how it is stored on the file system.
Objects contained within the configuration support the following properties:
| Key | Type | Required | Description |
|---|---|---|---|
| path | String | No | The URL path where the static file will be accessible from. |
| contentType | String | No | The value of the HTTP response header that will be served with the static file. |
The following example shows an override configuration where an HTML file can be accessed without the file extension:
.vercel/output/config.json
The property is an array of file paths and/or glob patterns that should be re-populated within the build sandbox upon subsequent Deployments.
Note that this property is only relevant when Vercel is building a Project from source code, meaning it is not relevant when building locally or when creating a Deployment from "prebuilt" build artifacts.
.vercel/output/config.json
The optional property is an object describing the framework of the built outputs.
This value is used for display purposes only.
.vercel/output/config.json
The optional property is an object describing the cron jobs for the production deployment of a project.
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