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Checks API

Learn how Checks API helps you with Vercel Integrations.

The Vercel Checks API let you create tests and assertions that run after each deployment has been built. They are powered by Integrations, which allow you to connect any third-party service of your choice with Vercel.

Once the Checks API start implementing on your deployment, its status is set to running. Updating the Check with a conclusion will automatically set the Check status to completed. This results in a successful deployment.

However, your deployment will fail if the conclusion updates to one of the following values:

Conclusion
blocking equals to true
 cancelled
Yes
 failed
Yes
 neutral
No
 succeeded
No
 skipped
No

Vercel's Checks API is capable of generating rich output results that can store arbitrary data, Web Vitals and a Virtual Experience Score through the output property.

To include Web Vitals and a Virtual Experience Score, the following can be passed to output under a metrics field:

Key
Type
Description
TBT
Map
The Total Blocking Time, as measured by the Check
LCP
Map
The Largest Contentful Paint, as measured by the Check
FCP
Map
The First Contentful Paint, as measured by the Check
CLS
Map
The Cumulative Layout Shift, as measured by the Check
virtualExperienceScore
Map
The overall Virtual Experience Score measured by the Check

Each of these has the following properties:

Key
Type
Description
value
Float
The value measured for the particular metric, in milliseconds. For virtualExperienceScore this value is the percentage between 0 and 1
previousValue
Float
A previous value for comparison purposes.
source
Enum
web-vitals