diff --git a/src/generator.ts b/src/generator.ts
index b4ef1931..9059538f 100644
--- a/src/generator.ts
+++ b/src/generator.ts
@@ -107,22 +107,19 @@ function declareNamedTypes(ast: AST, options: Options, rootASTName: string, proc
   }
 
   processed.add(ast)
-  let type = ''
 
   switch (ast.type) {
     case 'ARRAY':
-      type = [
+      return [
         declareNamedTypes(ast.params, options, rootASTName, processed),
         hasStandaloneName(ast) ? generateStandaloneType(ast, options) : undefined
       ]
         .filter(Boolean)
         .join('\n')
-      break
     case 'ENUM':
-      type = ''
-      break
+      return ''
     case 'INTERFACE':
-      type = getSuperTypesAndParams(ast)
+      return getSuperTypesAndParams(ast)
         .map(
           ast =>
             (ast.standaloneName === rootASTName || options.declareExternallyReferenced) &&
@@ -130,11 +127,10 @@ function declareNamedTypes(ast: AST, options: Options, rootASTName: string, proc
         )
         .filter(Boolean)
         .join('\n')
-      break
     case 'INTERSECTION':
     case 'TUPLE':
     case 'UNION':
-      type = [
+      return [
         hasStandaloneName(ast) ? generateStandaloneType(ast, options) : undefined,
         ast.params
           .map(ast => declareNamedTypes(ast, options, rootASTName, processed))
@@ -146,14 +142,12 @@ function declareNamedTypes(ast: AST, options: Options, rootASTName: string, proc
       ]
         .filter(Boolean)
         .join('\n')
-      break
     default:
       if (hasStandaloneName(ast)) {
-        type = generateStandaloneType(ast, options)
+        return generateStandaloneType(ast, options)
       }
+      return ''
   }
-
-  return type
 }
 
 function generateTypeUnmemoized(ast: AST, options: Options): string {
diff --git a/src/index.ts b/src/index.ts
index d8f68611..cc4cfbc7 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -165,25 +165,13 @@ export async function compile(schema: JSONSchema4, name: string, options: Partia
   }
 
   const normalized = normalize(linked, name, _options)
-  if (process.env.VERBOSE) {
-    if (isDeepStrictEqual(linked, normalized)) {
-      log('yellow', 'normalizer', time(), '✅ No change')
-    } else {
-      log('yellow', 'normalizer', time(), '✅ Result:', normalized)
-    }
-  }
+  log('yellow', 'normalizer', time(), '✅ Result:', normalized)
 
   const parsed = parse(normalized, _options)
   log('blue', 'parser', time(), '✅ Result:', parsed)
 
   const optimized = optimize(parsed, _options)
-  if (process.env.VERBOSE) {
-    if (isDeepStrictEqual(parsed, optimized)) {
-      log('cyan', 'optimizer', time(), '✅ No change')
-    } else {
-      log('cyan', 'optimizer', time(), '✅ Result:', optimized)
-    }
-  }
+  log('cyan', 'optimizer', time(), '✅ Result:', optimized)
 
   const generated = generate(optimized, _options)
   log('magenta', 'generator', time(), '✅ Result:', generated)
diff --git a/src/normalizer.ts b/src/normalizer.ts
index 57b496e2..e74bef4b 100644
--- a/src/normalizer.ts
+++ b/src/normalizer.ts
@@ -1,5 +1,5 @@
 import {JSONSchemaTypeName, LinkedJSONSchema, NormalizedJSONSchema, Parent} from './types/JSONSchema'
-import {appendToDescription, escapeBlockComment, justName, toSafeString, traverse} from './utils'
+import {appendToDescription, escapeBlockComment, isSchemaLike, justName, toSafeString, traverse} from './utils'
 import {Options} from './'
 
 type Rule = (schema: LinkedJSONSchema, fileName: string, options: Options) => void
@@ -50,10 +50,25 @@ rules.set('Default additionalProperties', (schema, _, options) => {
   }
 })
 
-rules.set('Default top level `id`', (schema, fileName) => {
+rules.set('Transform id to $id', (schema, fileName) => {
+  if (!isSchemaLike(schema)) {
+    return
+  }
+  if (schema.id && schema.$id && schema.id !== schema.$id) {
+    throw ReferenceError(
+      `Schema must define either id or $id, not both. Given id=${schema.id}, $id=${schema.$id} in ${fileName}`
+    )
+  }
+  if (schema.id) {
+    schema.$id = schema.id
+    delete schema.id
+  }
+})
+
+rules.set('Default top level $id', (schema, fileName) => {
   const isRoot = schema[Parent] === null
-  if (isRoot && !schema.id) {
-    schema.id = toSafeString(justName(fileName))
+  if (isRoot && !schema.$id) {
+    schema.$id = toSafeString(justName(fileName))
   }
 })
 
diff --git a/src/parser.ts b/src/parser.ts
index 6cb6cef3..55ffa037 100644
--- a/src/parser.ts
+++ b/src/parser.ts
@@ -51,9 +51,9 @@ export function parse(
   // so that it gets first pick for standalone name.
   const ast = parseAsTypeWithCache(
     {
+      $id: schema.$id,
       allOf: [],
       description: schema.description,
-      id: schema.id,
       title: schema.title
     },
     'ALL_OF',
@@ -247,7 +247,7 @@ function parseNonLiteral(
         keyName,
         standaloneName: standaloneName(schema, keyNameFromDefinition, usedNames),
         params: (schema.type as JSONSchema4TypeName[]).map(type => {
-          const member: LinkedJSONSchema = {...omit(schema, 'description', 'id', 'title'), type}
+          const member: LinkedJSONSchema = {...omit(schema, '$id', 'description', 'title'), type}
           return parse(maybeStripDefault(member as any), options, undefined, processed, usedNames)
         }),
         type: 'UNION'
@@ -300,7 +300,7 @@ function standaloneName(
   keyNameFromDefinition: string | undefined,
   usedNames: UsedNames
 ): string | undefined {
-  const name = schema.title || schema.id || keyNameFromDefinition
+  const name = schema.title || schema.$id || keyNameFromDefinition
   if (name) {
     return generateName(name, usedNames)
   }
diff --git a/src/types/JSONSchema.ts b/src/types/JSONSchema.ts
index d11d099f..da5f56d5 100644
--- a/src/types/JSONSchema.ts
+++ b/src/types/JSONSchema.ts
@@ -87,6 +87,9 @@ export interface NormalizedJSONSchema extends LinkedJSONSchema {
   oneOf?: NormalizedJSONSchema[]
   not?: NormalizedJSONSchema
   required: string[]
+
+  // Removed by normalizer
+  id: never
 }
 
 export interface EnumJSONSchema extends NormalizedJSONSchema {
@@ -114,15 +117,13 @@ export interface CustomTypeJSONSchema extends NormalizedJSONSchema {
   tsType: string
 }
 
-export const getRootSchema = memoize(
-  (schema: LinkedJSONSchema): LinkedJSONSchema => {
-    const parent = schema[Parent]
-    if (!parent) {
-      return schema
-    }
-    return getRootSchema(parent)
+export const getRootSchema = memoize((schema: LinkedJSONSchema): LinkedJSONSchema => {
+  const parent = schema[Parent]
+  if (!parent) {
+    return schema
   }
-)
+  return getRootSchema(parent)
+})
 
 export function isPrimitive(schema: LinkedJSONSchema | JSONSchemaType): schema is JSONSchemaType {
   return !isPlainObject(schema)
diff --git a/src/typesOfSchema.ts b/src/typesOfSchema.ts
index 130c5665..19d56bb9 100644
--- a/src/typesOfSchema.ts
+++ b/src/typesOfSchema.ts
@@ -65,7 +65,7 @@ const matchers: Record<SchemaType, (schema: JSONSchema) => boolean> = {
     return 'enum' in schema && 'tsEnumNames' in schema
   },
   NAMED_SCHEMA(schema) {
-    return 'id' in schema && ('patternProperties' in schema || 'properties' in schema)
+    return '$id' in schema && ('patternProperties' in schema || 'properties' in schema)
   },
   NULL(schema) {
     return schema.type === 'null'
diff --git a/src/utils.ts b/src/utils.ts
index 184d3166..2fe7fa86 100644
--- a/src/utils.ts
+++ b/src/utils.ts
@@ -1,6 +1,6 @@
 import {deburr, isPlainObject, trim, upperFirst} from 'lodash'
 import {basename, dirname, extname, join, normalize, sep} from 'path'
-import {JSONSchema, LinkedJSONSchema} from './types/JSONSchema'
+import {JSONSchema, LinkedJSONSchema, Parent} from './types/JSONSchema'
 
 // TODO: pull out into a separate package
 export function Try<T>(fn: () => T, err: (e: Error) => any): T {
@@ -79,8 +79,6 @@ export function traverse(
     return
   }
 
-  // console.log('key', key + '\n')
-
   processed.add(schema)
   callback(schema, key ?? null)
 
@@ -328,19 +326,19 @@ export function maybeStripDefault(schema: LinkedJSONSchema): LinkedJSONSchema {
 }
 
 /**
- * Removes the schema's `id`, `name`, and `description` properties
+ * Removes the schema's `$id`, `name`, and `description` properties
  * if they exist.
  * Useful when parsing intersections.
  *
  * Mutates `schema`.
  */
 export function maybeStripNameHints(schema: JSONSchema): JSONSchema {
+  if ('$id' in schema) {
+    delete schema.$id
+  }
   if ('description' in schema) {
     delete schema.description
   }
-  if ('id' in schema) {
-    delete schema.id
-  }
   if ('name' in schema) {
     delete schema.name
   }
@@ -353,3 +351,31 @@ export function appendToDescription(existingDescription: string | undefined, ...
   }
   return values.join('\n')
 }
+
+export function isSchemaLike(schema: LinkedJSONSchema) {
+  if (!isPlainObject(schema)) {
+    return false
+  }
+  const parent = schema[Parent]
+  if (parent === null) {
+    return true
+  }
+
+  const JSON_SCHEMA_KEYWORDS = [
+    'allOf',
+    'anyOf',
+    'dependencies',
+    'enum',
+    'oneOf',
+    'definitions',
+    'not',
+    'patternProperties',
+    'properties',
+    'required'
+  ]
+  if (JSON_SCHEMA_KEYWORDS.some(_ => parent[_] === schema)) {
+    return false
+  }
+
+  return true
+}
diff --git a/test/__snapshots__/test/test.ts.md b/test/__snapshots__/test/test.ts.md
index c48a3d3d..f27f9d47 100644
--- a/test/__snapshots__/test/test.ts.md
+++ b/test/__snapshots__/test/test.ts.md
@@ -697,6 +697,7 @@ Generated by [AVA](https://avajs.dev).
      */␊
     ␊
     export type LastName = string;␊
+    export type Height = number;␊
     ␊
     export interface ExampleSchema {␊
       firstName: string;␊
@@ -705,7 +706,7 @@ Generated by [AVA](https://avajs.dev).
        * Age in years␊
        */␊
       age?: number;␊
-      height?: number;␊
+      height?: Height;␊
       favoriteFoods?: unknown[];␊
       likesDogs?: boolean;␊
       [k: string]: unknown;␊
diff --git a/test/__snapshots__/test/test.ts.snap b/test/__snapshots__/test/test.ts.snap
index 5bfe27d0..d318cdfc 100644
Binary files a/test/__snapshots__/test/test.ts.snap and b/test/__snapshots__/test/test.ts.snap differ
diff --git a/test/e2e/basics.ts b/test/e2e/basics.ts
index 1c3dade3..25bf3e0e 100644
--- a/test/e2e/basics.ts
+++ b/test/e2e/basics.ts
@@ -15,6 +15,7 @@ export const input = {
       minimum: 0
     },
     height: {
+      $id: 'height',
       type: 'number'
     },
     favoriteFoods: {
diff --git a/test/normalizer/addEmptyRequiredProperty.json b/test/normalizer/addEmptyRequiredProperty.json
index 6a4fa123..1495f2f3 100644
--- a/test/normalizer/addEmptyRequiredProperty.json
+++ b/test/normalizer/addEmptyRequiredProperty.json
@@ -1,23 +1,25 @@
 {
   "name": "Add empty `required` property if none is defined",
   "in": {
-    "id": "foo",
-    "type": ["object"],
+    "$id": "foo",
+    "type": [
+      "object"
+    ],
     "properties": {
       "a": {
         "type": "integer",
-        "id": "a"
+        "$id": "a"
       }
     },
     "additionalProperties": true
   },
   "out": {
-    "id": "foo",
+    "$id": "foo",
     "type": "object",
     "properties": {
       "a": {
         "type": "integer",
-        "id": "a"
+        "$id": "a"
       }
     },
     "additionalProperties": true,
diff --git a/test/normalizer/constToEnum.json b/test/normalizer/constToEnum.json
index 9e3567c6..8251b5dd 100644
--- a/test/normalizer/constToEnum.json
+++ b/test/normalizer/constToEnum.json
@@ -1,11 +1,13 @@
 {
   "name": "Normalize const to singleton enum",
   "in": {
-    "id": "foo",
+    "$id": "foo",
     "const": "foobar"
   },
   "out": {
-    "id": "foo",
-    "enum": ["foobar"]
+    "$id": "foo",
+    "enum": [
+      "foobar"
+    ]
   }
 }
diff --git a/test/normalizer/defaultAdditionalProperties.2.json b/test/normalizer/defaultAdditionalProperties.2.json
index 460b610c..a6a98f14 100644
--- a/test/normalizer/defaultAdditionalProperties.2.json
+++ b/test/normalizer/defaultAdditionalProperties.2.json
@@ -1,14 +1,14 @@
 {
   "name": "Default additionalProperties to false",
   "in": {
-    "id": "foo",
+    "$id": "foo",
     "type": [
       "object"
     ],
     "properties": {
       "a": {
         "type": "integer",
-        "id": "a"
+        "$id": "a"
       },
       "b": {
         "type": "object"
@@ -20,12 +20,12 @@
     "additionalProperties": false
   },
   "out": {
-    "id": "foo",
+    "$id": "foo",
     "type": "object",
     "properties": {
       "a": {
         "type": "integer",
-        "id": "a"
+        "$id": "a"
       },
       "b": {
         "additionalProperties": false,
diff --git a/test/normalizer/defaultAdditionalProperties.json b/test/normalizer/defaultAdditionalProperties.json
index 854004f6..a4963c8e 100644
--- a/test/normalizer/defaultAdditionalProperties.json
+++ b/test/normalizer/defaultAdditionalProperties.json
@@ -1,23 +1,25 @@
 {
   "name": "Default additionalProperties to true",
   "in": {
-    "id": "foo",
-    "type": ["object"],
+    "$id": "foo",
+    "type": [
+      "object"
+    ],
     "properties": {
       "a": {
         "type": "integer",
-        "id": "a"
+        "$id": "a"
       }
     },
     "required": []
   },
   "out": {
-    "id": "foo",
+    "$id": "foo",
     "type": "object",
     "properties": {
       "a": {
         "type": "integer",
-        "id": "a"
+        "$id": "a"
       }
     },
     "required": [],
diff --git a/test/normalizer/defaultID.json b/test/normalizer/defaultID.1.json
similarity index 59%
rename from test/normalizer/defaultID.json
rename to test/normalizer/defaultID.1.json
index 214e81cd..0f29537c 100644
--- a/test/normalizer/defaultID.json
+++ b/test/normalizer/defaultID.1.json
@@ -1,15 +1,19 @@
 {
-  "name": "Default top level `id`",
+  "name": "Default top level `id` (1)",
   "in": {
     "friend": {
       "properties": {
         "knowsFrom": {
-          "enum": ["work", "school", "other"]
+          "enum": [
+            "work",
+            "school",
+            "other"
+          ]
         }
       },
       "additionalProperties": true,
       "required": [],
-      "id": "friend"
+      "$id": "friend"
     },
     "properties": {
       "firstName": {
@@ -17,18 +21,25 @@
       }
     },
     "additionalProperties": true,
-    "required": ["firstName"]
+    "required": [
+      "firstName"
+    ]
   },
   "out": {
+    "$id": "DefaultID1",
     "friend": {
       "properties": {
         "knowsFrom": {
-          "enum": ["work", "school", "other"]
+          "enum": [
+            "work",
+            "school",
+            "other"
+          ]
         }
       },
       "additionalProperties": true,
       "required": [],
-      "id": "friend"
+      "$id": "friend"
     },
     "properties": {
       "firstName": {
@@ -36,7 +47,8 @@
       }
     },
     "additionalProperties": true,
-    "required": ["firstName"],
-    "id": "DefaultID"
+    "required": [
+      "firstName"
+    ]
   }
 }
diff --git a/test/normalizer/defaultID.2.json b/test/normalizer/defaultID.2.json
new file mode 100644
index 00000000..c2b749a4
--- /dev/null
+++ b/test/normalizer/defaultID.2.json
@@ -0,0 +1,55 @@
+{
+  "name": "Default top level `id` (2)",
+  "in": {
+    "$id": "DefaultID",
+    "friend": {
+      "properties": {
+        "knowsFrom": {
+          "enum": [
+            "work",
+            "school",
+            "other"
+          ]
+        }
+      },
+      "additionalProperties": true,
+      "required": [],
+      "$id": "friend"
+    },
+    "properties": {
+      "firstName": {
+        "type": "string"
+      }
+    },
+    "additionalProperties": true,
+    "required": [
+      "firstName"
+    ]
+  },
+  "out": {
+    "$id": "DefaultID",
+    "friend": {
+      "properties": {
+        "knowsFrom": {
+          "enum": [
+            "work",
+            "school",
+            "other"
+          ]
+        }
+      },
+      "additionalProperties": true,
+      "required": [],
+      "$id": "friend"
+    },
+    "properties": {
+      "firstName": {
+        "type": "string"
+      }
+    },
+    "additionalProperties": true,
+    "required": [
+      "firstName"
+    ]
+  }
+}
diff --git a/test/normalizer/destructureUnaryTypes.json b/test/normalizer/destructureUnaryTypes.json
index f9c05628..2f7df972 100644
--- a/test/normalizer/destructureUnaryTypes.json
+++ b/test/normalizer/destructureUnaryTypes.json
@@ -1,36 +1,42 @@
 {
   "name": "Destructure unary types",
   "in": {
-    "id": "foo",
-    "type": ["object"],
+    "$id": "foo",
+    "type": [
+      "object"
+    ],
     "definitions": {
       "a": {
-        "type": ["integer"],
-        "id": "a"
+        "type": [
+          "integer"
+        ],
+        "$id": "a"
       }
     },
     "properties": {
       "b": {
-        "type": ["string"],
-        "id": "b"
+        "type": [
+          "string"
+        ],
+        "$id": "b"
       }
     },
     "additionalProperties": true,
     "required": []
   },
   "out": {
-    "id": "foo",
+    "$id": "foo",
     "type": "object",
     "definitions": {
       "a": {
         "type": "integer",
-        "id": "a"
+        "$id": "a"
       }
     },
     "properties": {
       "b": {
         "type": "string",
-        "id": "b"
+        "$id": "b"
       }
     },
     "additionalProperties": true,
diff --git a/test/normalizer/emptyStringConstToEnum.json b/test/normalizer/emptyStringConstToEnum.json
index 87293397..a7ecee21 100644
--- a/test/normalizer/emptyStringConstToEnum.json
+++ b/test/normalizer/emptyStringConstToEnum.json
@@ -1,11 +1,13 @@
 {
   "name": "Normalize empty const to singleton enum",
   "in": {
-    "id": "foo",
+    "$id": "foo",
     "const": ""
   },
   "out": {
-    "id": "foo",
-    "enum": [""]
+    "$id": "foo",
+    "enum": [
+      ""
+    ]
   }
 }
diff --git a/test/normalizer/nonObjectItems.json b/test/normalizer/nonObjectItems.json
index 12cdbdfa..f86e0ecf 100644
--- a/test/normalizer/nonObjectItems.json
+++ b/test/normalizer/nonObjectItems.json
@@ -1,7 +1,7 @@
 {
   "name": "Non object items.items",
   "in": {
-    "id": "foo",
+    "$id": "foo",
     "type": "object",
     "properties": {
       "myProperty": {
@@ -12,7 +12,7 @@
     "additionalProperties": false
   },
   "out": {
-    "id": "foo",
+    "$id": "foo",
     "type": "object",
     "properties": {
       "myProperty": {
diff --git a/test/normalizer/defsToDefinitions.json b/test/normalizer/normalizeDefs.json
similarity index 64%
rename from test/normalizer/defsToDefinitions.json
rename to test/normalizer/normalizeDefs.json
index 050ca47f..c8eb3895 100644
--- a/test/normalizer/defsToDefinitions.json
+++ b/test/normalizer/normalizeDefs.json
@@ -1,14 +1,14 @@
 {
   "name": "Normalize $defs to definitions",
   "in": {
-    "id": "foo",
-    "$defs" : {
+    "$id": "foo",
+    "$defs": {
       "bar": "baz"
     }
   },
   "out": {
-    "id": "foo",
-    "definitions" : {
+    "$id": "foo",
+    "definitions": {
       "bar": "baz"
     }
   }
diff --git a/test/normalizer/normalizeExtends.json b/test/normalizer/normalizeExtends.json
index d0fc19d6..b6e6f940 100644
--- a/test/normalizer/normalizeExtends.json
+++ b/test/normalizer/normalizeExtends.json
@@ -1,14 +1,14 @@
 {
   "name": "Normalize extends to an array",
   "in": {
-    "id": "foo",
+    "$id": "foo",
     "extends": "foo",
     "type": "object",
     "required": [],
     "additionalProperties": true
   },
   "out": {
-    "id": "foo",
+    "$id": "foo",
     "extends": [
       "foo"
     ],
diff --git a/test/normalizer/normalizeID.json b/test/normalizer/normalizeID.json
new file mode 100644
index 00000000..95d3e19f
--- /dev/null
+++ b/test/normalizer/normalizeID.json
@@ -0,0 +1,29 @@
+{
+  "name": "Transform id to $id",
+  "in": {
+    "properties": {
+      "b": {
+        "id": "b",
+        "type": "object",
+        "additionalProperties": false,
+        "required": []
+      }
+    },
+    "additionalProperties": false,
+    "required": [],
+    "id": "a"
+  },
+  "out": {
+    "properties": {
+      "b": {
+        "$id": "b",
+        "type": "object",
+        "additionalProperties": false,
+        "required": []
+      }
+    },
+    "additionalProperties": false,
+    "required": [],
+    "$id": "a"
+  }
+}
diff --git a/test/normalizer/redundantNull.json b/test/normalizer/redundantNull.json
index 8ff6060b..bfad6e30 100644
--- a/test/normalizer/redundantNull.json
+++ b/test/normalizer/redundantNull.json
@@ -4,40 +4,71 @@
     "type": "object",
     "properties": {
       "noopMissingType": {
-        "enum": ["foo", "bar"]
+        "enum": [
+          "foo",
+          "bar"
+        ]
       },
       "noopMissingEnum": {
-        "type": ["null", "string"]
+        "type": [
+          "null",
+          "string"
+        ]
       },
       "noopNonNullableEnum": {
         "type": "string",
-        "enum": ["foo", "bar", null]
+        "enum": [
+          "foo",
+          "bar",
+          null
+        ]
       },
       "dedupeNulls": {
-        "type": ["null", "string"],
-        "enum": ["foo", "bar", null]
+        "type": [
+          "null",
+          "string"
+        ],
+        "enum": [
+          "foo",
+          "bar",
+          null
+        ]
       }
     }
   },
   "out": {
     "additionalProperties": true,
-    "id": "RedundantNull",
+    "$id": "RedundantNull",
     "required": [],
     "type": "object",
     "properties": {
       "noopMissingType": {
-        "enum": ["foo", "bar"]
+        "enum": [
+          "foo",
+          "bar"
+        ]
       },
       "noopMissingEnum": {
-        "type": ["null", "string"]
+        "type": [
+          "null",
+          "string"
+        ]
       },
       "noopNonNullableEnum": {
         "type": "string",
-        "enum": ["foo", "bar", null]
+        "enum": [
+          "foo",
+          "bar",
+          null
+        ]
       },
       "dedupeNulls": {
         "type": "string",
-        "enum": ["foo", "bar", null]
+        "enum": [
+          "foo",
+          "bar",
+          null
+        ]
       }
     }
   }
diff --git a/test/normalizer/removeEmptyExtends.1.json b/test/normalizer/removeEmptyExtends.1.json
index 17382b5e..ae1aa3e5 100644
--- a/test/normalizer/removeEmptyExtends.1.json
+++ b/test/normalizer/removeEmptyExtends.1.json
@@ -1,14 +1,14 @@
 {
   "name": "Remove empty extends (1)",
   "in": {
-    "id": "foo",
+    "$id": "foo",
     "extends": [],
     "type": "object",
     "required": [],
     "additionalProperties": true
   },
   "out": {
-    "id": "foo",
+    "$id": "foo",
     "type": "object",
     "required": [],
     "additionalProperties": true
diff --git a/test/normalizer/removeEmptyExtends.2.json b/test/normalizer/removeEmptyExtends.2.json
index 77c72e19..bc668866 100644
--- a/test/normalizer/removeEmptyExtends.2.json
+++ b/test/normalizer/removeEmptyExtends.2.json
@@ -1,14 +1,14 @@
 {
   "name": "Remove empty extends (2)",
   "in": {
-    "id": "foo",
+    "$id": "foo",
     "extends": null,
     "type": "object",
     "required": [],
     "additionalProperties": true
   },
   "out": {
-    "id": "foo",
+    "$id": "foo",
     "type": "object",
     "required": [],
     "additionalProperties": true
diff --git a/test/normalizer/removeMaxItems.1.json b/test/normalizer/removeMaxItems.1.json
index b01fe130..01fa7e1d 100644
--- a/test/normalizer/removeMaxItems.1.json
+++ b/test/normalizer/removeMaxItems.1.json
@@ -2,7 +2,7 @@
   "name": "Remove maxItems if it is big enough to likely cause OOMs (1)",
   "in": {
     "additionalProperties": false,
-    "id": "RemoveMaxItems",
+    "$id": "RemoveMaxItems",
     "properties": {
       "a": {
         "minItems": 5,
@@ -31,7 +31,7 @@
   },
   "out": {
     "additionalProperties": false,
-    "id": "RemoveMaxItems",
+    "$id": "RemoveMaxItems",
     "properties": {
       "a": {
         "description": "@minItems 5",
diff --git a/test/normalizer/removeMaxItems.2.json b/test/normalizer/removeMaxItems.2.json
index fe6d93da..7625d859 100644
--- a/test/normalizer/removeMaxItems.2.json
+++ b/test/normalizer/removeMaxItems.2.json
@@ -2,7 +2,7 @@
   "name": "Remove maxItems if it is big enough to likely cause OOMs (2)",
   "in": {
     "additionalProperties": false,
-    "id": "RemoveMaxItems",
+    "$id": "RemoveMaxItems",
     "properties": {
       "a": {
         "minItems": 5,
@@ -31,7 +31,7 @@
   },
   "out": {
     "additionalProperties": false,
-    "id": "RemoveMaxItems",
+    "$id": "RemoveMaxItems",
     "properties": {
       "a": {
         "description": "@minItems 5",
diff --git a/test/normalizer/removeMaxItems.3.json b/test/normalizer/removeMaxItems.3.json
index 6f137477..ad73854b 100644
--- a/test/normalizer/removeMaxItems.3.json
+++ b/test/normalizer/removeMaxItems.3.json
@@ -2,7 +2,7 @@
   "name": "Remove maxItems if it is big enough to likely cause OOMs (3)",
   "in": {
     "additionalProperties": false,
-    "id": "RemoveMaxItems",
+    "$id": "RemoveMaxItems",
     "properties": {
       "a": {
         "description": "Test",
@@ -33,7 +33,7 @@
   },
   "out": {
     "additionalProperties": false,
-    "id": "RemoveMaxItems",
+    "$id": "RemoveMaxItems",
     "properties": {
       "a": {
         "description": "Test\n\n@minItems 5",
diff --git a/test/normalizer/schemaIgnoreMaxMinItems.json b/test/normalizer/schemaIgnoreMaxMinItems.json
index 3cfe53c4..a9efb778 100644
--- a/test/normalizer/schemaIgnoreMaxMinItems.json
+++ b/test/normalizer/schemaIgnoreMaxMinItems.json
@@ -4,7 +4,7 @@
     "ignoreMinAndMaxItems": true
   },
   "in": {
-    "id": "foo",
+    "$id": "foo",
     "type": "object",
     "properties": {
       "untyped": {
@@ -162,7 +162,7 @@
     "required": []
   },
   "out": {
-    "id": "foo",
+    "$id": "foo",
     "type": "object",
     "properties": {
       "untyped": {
diff --git a/test/normalizer/schemaItems.json b/test/normalizer/schemaItems.json
index c4ec54ad..e7ced8ae 100644
--- a/test/normalizer/schemaItems.json
+++ b/test/normalizer/schemaItems.json
@@ -1,7 +1,7 @@
 {
   "name": "Normalize schema.items",
   "in": {
-    "id": "foo",
+    "$id": "foo",
     "type": "object",
     "properties": {
       "untypedUnbounded": {
@@ -79,7 +79,7 @@
     "additionalProperties": false
   },
   "out": {
-    "id": "foo",
+    "$id": "foo",
     "type": "object",
     "properties": {
       "untypedUnbounded": {
diff --git a/test/normalizer/schemaMinItems.json b/test/normalizer/schemaMinItems.json
index c64cb8c8..dbdfba87 100644
--- a/test/normalizer/schemaMinItems.json
+++ b/test/normalizer/schemaMinItems.json
@@ -1,7 +1,7 @@
 {
   "name": "Normalise schema.minItems",
   "in": {
-    "id": "foo",
+    "$id": "foo",
     "type": "object",
     "properties": {
       "untyped": {
@@ -159,7 +159,7 @@
     "required": []
   },
   "out": {
-    "id": "foo",
+    "$id": "foo",
     "type": "object",
     "properties": {
       "untyped": {
diff --git a/test/testUtils.ts b/test/testUtils.ts
index e7442280..8876a267 100644
--- a/test/testUtils.ts
+++ b/test/testUtils.ts
@@ -1,5 +1,7 @@
 import test from 'ava'
-import {pathTransform, generateName} from '../src/utils'
+import {link} from '../src/linker'
+import {LinkedJSONSchema} from '../src/types/JSONSchema'
+import {pathTransform, generateName, isSchemaLike} from '../src/utils'
 
 export function run() {
   test('pathTransform', t => {
@@ -20,4 +22,27 @@ export function run() {
     t.is(generateName('a', usedNames), 'A2')
     t.is(generateName('a', usedNames), 'A3')
   })
+  test('isSchemaLike', t => {
+    const schema = link({
+      title: 'Example Schema',
+      type: 'object',
+      properties: {
+        firstName: {
+          type: 'string'
+        },
+        lastName: {
+          id: 'lastName',
+          type: 'string'
+        }
+      },
+      required: ['firstName', 'lastName']
+    })
+    t.is(isSchemaLike(schema), true)
+    t.is(isSchemaLike([] as any as LinkedJSONSchema), false)
+    t.is(isSchemaLike(schema.properties as LinkedJSONSchema), false)
+    t.is(isSchemaLike(schema.required as any as LinkedJSONSchema), false)
+    t.is(isSchemaLike(schema.title as any as LinkedJSONSchema), false)
+    t.is(isSchemaLike(schema.properties!.firstName), true)
+    t.is(isSchemaLike(schema.properties!.lastName), true)
+  })
 }