well-known-specification.md

​​The "tpcd/grace-period.json" Well-Known Resource Identifier

This page describes the use and content of URIs with the path /.well-known/tpcd/grace-period.json.

Use

A site currently in the third-party cookies Deprecation Trial grace period might express interest in a staged rollout of the long-term behavior (Deprecation Trial tokens or a privacy-preserving API). Such sites can host this well-known resource to opt out of the grace period for a percentage of clients, in order to avert widespread, unintended breakage on end-user experience if there are issues with the intended replacement.

Content

The /.well-known/tpcd/grace-period.json resource must follow the JSON schema stated below:

{
  "type": "object",
  "anyOf": [
    {
      "required": ["FirstPartyOptOutPercentage"]
    },
    {
      "required": ["ThirdPartyOptOutPercentage"]
    }
  ],
  "properties": {
    "FirstPartyOptOutPercentage": {
      "type": "integer",
      "enum": [0, 25, 50, 100]
    },
    "ThirdPartyOptOutPercentage": {
      "type": "integer",
      "enum": [0, 25, 50, 100]
    }
  }
}

"FirstPartyOptOutPercentage" denotes the site's opt-out value when it is in a top-level context embedding third-party cookies. For instance, if site example.com is enrolled in the first-party Deprecation Trial grace period, the FirstPartyOptOutPercentage on example.com/.well-known/tpcd/grace-period.json represents what % of Chrome clients opt out of the grace period and have third-party cookies blocked when embedded on example.com.

"ThirdPartyOptOutPercentage" denotes the site's opt-out value when it is using third-party cookies in an embedded context. For instance, if site example.com is enrolled in the third-party Deprecation Trial grace period, the ThirdPartyOptOutPercentage on example.com/.well-known/tpcd/grace-period.json represents what % of Chrome clients opt out of the grace period and have third-party cookies blocked when a cross-site host embeds an example.com iframe.

The grace-period.json file must be well formed in order to take effect. To avoid errors, check your file content with the grace period opt-out validation tool.