#JSON

Use JSON resources for extension features like rulesets and managed schemas with validation and predictable output handling.

Extension.js processes manifest-referenced JSON resources, validates them for known feature types, watches them during development, and emits output assets when needed.

#JSON capabilities

#JSON support

Common manifest fields:

#Sample JSON declaration in manifest.json

Here's an example of how to declare a JSON file in your manifest.json:

{
  "manifest_version": 3,
  "name": "My Extension",
  "version": "1.0.0",
  "declarative_net_request": {
    "rule_resources": [
      {
        "id": "ruleset_1",
        "enabled": true,
        "path": "rules/ruleset.json"
      }
    ]
  },
  "storage": {
    "managed_schema": "schema/storage-schema.json"
  }
}

#Output path

JSON resources are emitted by feature context (for example DNR and storage schema outputs):

declarative_net_request/<ruleset-id>.json
storage/managed_schema.json

#Development behavior

• Manifest-referenced JSON files are tracked as file dependencies.
• JSON edits trigger recompilation.
• Some JSON-related structural manifest changes can require restart diagnostics.

#Validation behavior

Extension.js validates:

• JSON syntax for referenced resources
• DNR ruleset shape (array-based ruleset expectations)
• managed storage schema shape (object-based expectations)

#Environment placeholders

Emitted .json assets can receive $EXTENSION_* placeholder replacement during compilation (same pass used for static HTML placeholder replacement).

#Best practices

• Keep manifest-referenced JSON focused on browser-required resource formats.
• Validate JSON resources in CI before packaging.
• Prefer stable file paths in manifest to reduce restart-required structural changes in development.
• For app data consumed by code, consider JSON imports in JS/TS modules separately from manifest resource JSON.

#Next steps

• Continue with icons in development.
• Learn about manifest development behavior.