diff --git a/src/hyperjump-json-schema.test.js b/src/hyperjump-json-schema.test.js
index 5a89947..de50e4b 100644
--- a/src/hyperjump-json-schema.test.js
+++ b/src/hyperjump-json-schema.test.js
@@ -11,6 +11,9 @@ import "@hyperjump/json-schema/draft-07";
 import "@hyperjump/json-schema/draft-06";
 import "@hyperjump/json-schema/draft-04";
 import "@hyperjump/json-schema/formats";
+import "@hyperjump/json-schema/openapi-3-0";
+import "@hyperjump/json-schema/openapi-3-1";
+import "@hyperjump/json-schema/openapi-3-2";
 import { BASIC } from "@hyperjump/json-schema/experimental";
 import { JSE, jsonSchemaErrors } from "../src/index.js";
 import { FluentBundle, FluentResource } from "@fluent/bundle";
@@ -55,8 +58,8 @@ import { translations } from "./translations/index.js";
  * }} TestSuite
  */
 
-/** @type (dialectUri: string, dialect: number) => void */
-const runTests = (dialectUri, dialect) => {
+/** @type (dialectUri: string, dialect: number, suites?: string[], skip?: Record<string, string[]>) => void */
+const runTests = (dialectUri, dialect, suites = ["tests"], skip = {}) => {
   describe(`JSON Schema Errors - ${dialectUri}`, async () => {
     setShouldValidateFormat(true);
 
@@ -66,33 +69,36 @@ const runTests = (dialectUri, dialect) => {
       unregisterSchema(schemaUri);
     });
 
-    for (const entry of await readdir(`${import.meta.dirname}/test-suite/tests`, { withFileTypes: true })) {
-      if (!entry.isFile() || !entry.name.endsWith(".json")) {
-        continue;
-      }
-
-      const file = `${entry.parentPath}/${entry.name}`;
-      const suite = /** @type TestSuite */ (JSON.parse(await readFile(file, "utf8")));
-
-      for (const testCase of suite.tests) {
-        if (!isCompatible(testCase.compatibility, dialect)) {
+    for (const suite of suites) {
+      for (const entry of await readdir(`${import.meta.dirname}/test-suite/${suite}`, { withFileTypes: true })) {
+        if (!entry.isFile() || !entry.name.endsWith(".json")) {
           continue;
         }
-        test(testCase.description, async () => {
-          registerSchema(testCase.schema, schemaUri, dialectUri);
 
-          const instance = testCase.instance;
-          const output = await validate(schemaUri, instance, BASIC);
-          const errors = await jsonSchemaErrors(output, schemaUri, instance, { isFormatAsserted: true });
+        const file = `${entry.parentPath}/${entry.name}`;
+        const testSuite = /** @type TestSuite */ (JSON.parse(await readFile(file, "utf8")));
 
-          expect(errors).to.eql(buildErrors(testCase.errors, schemaUri));
-          expectNestedLocations(errors);
+        for (const testCase of testSuite.tests) {
+          if (!isCompatible(testCase.compatibility, dialect)) {
+            continue;
+          }
+          const testOrSkip = skip[`${suite}/${entry.name}`]?.includes(testCase.description) ? test.skip : test;
+          testOrSkip(testCase.description, async () => {
+            registerSchema(testCase.schema, schemaUri, dialectUri);
 
-          const result = await validate(schemaUri, instance, JSE);
-          const fullResultsErrors = result.valid ? [] : result.errors;
-          expect(fullResultsErrors).to.eql(buildErrors(testCase.errorsWithFullResults ?? testCase.errors, schemaUri));
-          expectNestedLocations(fullResultsErrors);
-        });
+            const instance = testCase.instance;
+            const output = await validate(schemaUri, instance, BASIC);
+            const errors = await jsonSchemaErrors(output, schemaUri, instance, { isFormatAsserted: true });
+
+            expect(errors).to.eql(buildErrors(testCase.errors, schemaUri));
+            expectNestedLocations(errors);
+
+            const result = await validate(schemaUri, instance, JSE);
+            const fullResultsErrors = result.valid ? [] : result.errors;
+            expect(fullResultsErrors).to.eql(buildErrors(testCase.errorsWithFullResults ?? testCase.errors, schemaUri));
+            expectNestedLocations(fullResultsErrors);
+          });
+        }
       }
     }
   });
@@ -210,8 +216,98 @@ const getMessage = (function () {
   };
 }());
 
+/**
+ * OpenAPI 3.0 is draft-04 without some keywords, such as `patternProperties`,
+ * `dependencies`, `additionalItems`, and `$comment`. It also doesn't allow
+ * unknown keywords, `$defs`, array-form `items`, or an array `type`. These
+ * tests have schemas that aren't valid OpenAPI 3.0.
+ *
+ * @type Record<string, string[]>
+ */
+const oas30Skip = {
+  "tests/additionalProperties.json": [
+    "additionalProperties with false schema",
+    "additionalProperties with object schema",
+    "additionalProperties on a non-object",
+    "additionalProperties pass"
+  ],
+  "tests/anyOf.json": [
+    "anyOf with $ref alternatives filters by type"
+  ],
+  "tests/comment.json": [
+    "format"
+  ],
+  "tests/contains.json": [
+    "contains passing"
+  ],
+  "tests/dependencies.json": [
+    "array-form dependencies",
+    "array-form dependencies pass",
+    "schema-form dependencies",
+    "schema-form dependencies on a non-object",
+    "dependentSchemas pass",
+    "schem-form dependencies pass",
+    "schema-form and array-form dependencies together"
+  ],
+  "tests/enum.json": [
+    "enum with integer and string types filters fractions",
+    "enum with integer and string types passes for strings"
+  ],
+  "tests/items.json": [
+    "items/additionalItems with false schema",
+    "items/additionalItems with object schema",
+    "additionalItems on a non-array",
+    "additionalItems pass"
+  ],
+  "tests/not.json": [
+    "not with multiple types",
+    "not with dependencies",
+    "not with schema dependencies",
+    "not with an unknown keyword",
+    "not with schema dependencies when the property is absent",
+    "not with array-form items that aren't present",
+    "not with additionalItems",
+    "not with patternProperties that aren't present",
+    "not with descriptions nested too deeply to show"
+  ],
+  "tests/oneOf.json": [
+    "oneOf with $ref alternatives filters by type",
+    "oneOf more than one match with array-form items that aren't present",
+    "oneOf more than one match with patternProperties that aren't present"
+  ],
+  "tests/patternProperties.json": [
+    "patternProperties",
+    "patternProperties on a non-object",
+    "patternProperties pass"
+  ],
+  "tests/prefixItems.json": [
+    "array-form items",
+    "array-form items with fewer items than are defined",
+    "array-form items on an non-array",
+    "prefixItems pass",
+    "array-form items pass"
+  ],
+  "tests/propertyNames.json": [
+    "propertyNames pass"
+  ],
+  "tests/ref.json": [
+    "$ref",
+    "$ref pass"
+  ],
+  "tests/type.json": [
+    "multiple types",
+    "collapsed type errors"
+  ],
+  "tests/unknown.json": [
+    "unknown keyword"
+  ]
+};
+
 runTests("https://json-schema.org/draft/2020-12/schema", 2020);
 runTests("https://json-schema.org/draft/2019-09/schema", 2019);
 runTests("http://json-schema.org/draft-07/schema", 7);
 runTests("http://json-schema.org/draft-06/schema", 6);
 runTests("http://json-schema.org/draft-04/schema", 4);
+runTests("https://spec.openapis.org/oas/3.2/dialect", 2020, ["tests", "openapi"]);
+runTests("https://spec.openapis.org/oas/3.1/dialect/base", 2020, ["tests", "openapi"]);
+runTests("https://spec.openapis.org/oas/3.0/dialect", 4, ["tests", "openapi"], oas30Skip);
diff --git a/src/index.d.ts b/src/index.d.ts
index 621a5ef..da1dd28 100644
--- a/src/index.d.ts
+++ b/src/index.d.ts
@@ -59,6 +59,15 @@ export type KeywordDefinition<Value = unknown, Context extends EvaluationContext
    */
   annotation?: true;
 
+  /**
+   * The URI of a keyword that means the same thing. The keyword's results are
+   * normalized under that URI, so everything that handles that keyword handles
+   * this one too. The compiled values must have the same shape. For example,
+   * the OpenAPI 3.0 `type` keyword is an alias of the JSON Schema `type`
+   * keyword.
+   */
+  alias?: string;
+
   /**
    * The message for an occurrence of the keyword that failed.
    *
diff --git a/src/index.js b/src/index.js
index d739b61..d434762 100644
--- a/src/index.js
+++ b/src/index.js
@@ -92,6 +92,9 @@ defineKeyword("https://json-schema.org/keyword/comment", { annotation: true });
 defineKeyword("https://json-schema.org/keyword/const", {});
 defineKeyword("https://json-schema.org/keyword/contains", containsKeyword);
 defineKeyword("https://json-schema.org/keyword/draft-06/contains", containsDraft06Keyword);
+defineKeyword("https://json-schema.org/keyword/contentEncoding", { annotation: true });
+defineKeyword("https://json-schema.org/keyword/contentMediaType", { annotation: true });
+defineKeyword("https://json-schema.org/keyword/contentSchema", { annotation: true });
 defineKeyword("https://json-schema.org/keyword/default", { annotation: true });
 defineKeyword("https://json-schema.org/keyword/definitions", { annotation: true });
 defineKeyword("https://json-schema.org/keyword/draft-04/dependencies", dependenciesKeyword);
@@ -150,6 +153,15 @@ defineKeyword("https://json-schema.org/keyword/uniqueItems", {});
 defineKeyword("https://json-schema.org/keyword/unknown", { annotation: true });
 defineKeyword("https://json-schema.org/keyword/writeOnly", { annotation: true });
 
+// OpenAPI keywords
+defineKeyword("https://spec.openapis.org/oas/3.0/keyword/discriminator", { annotation: true });
+defineKeyword("https://spec.openapis.org/oas/3.0/keyword/example", { annotation: true });
+defineKeyword("https://spec.openapis.org/oas/3.0/keyword/externalDocs", { annotation: true });
+defineKeyword("https://spec.openapis.org/oas/3.0/keyword/nullable", { annotation: true });
+// Compiles `nullable` into its value, so it has the same shape as `type`
+defineKeyword("https://spec.openapis.org/oas/3.0/keyword/type", { alias: "https://json-schema.org/keyword/type" });
+defineKeyword("https://spec.openapis.org/oas/3.0/keyword/xml", { annotation: true });
+
 export {
   allTrue,
   countTrue,
diff --git a/src/json-schema-errors.js b/src/json-schema-errors.js
index b7f3a18..02a3246 100644
--- a/src/json-schema-errors.js
+++ b/src/json-schema-errors.js
@@ -35,6 +35,17 @@ export const jsonSchemaErrors = async (errorOutput, schemaUri, instance, options
 /** @type Record<string, API.KeywordDefinition<any>> */
 const keywordDefinitions = {};
 
+/**
+ * The URI a keyword's results are normalized under. An alias's results are
+ * normalized under the keyword it's an alias of.
+ *
+ * @type (keywordUri: string) => string
+ */
+export const toOutputKeywordUri = (keywordUri) => {
+  const normalizedKeywordUri = toAbsoluteIri(keywordUri);
+  return keywordDefinitions[normalizedKeywordUri]?.alias ?? normalizedKeywordUri;
+};
+
 /** @type (schemaLocation: string, ast: AST) => boolean */
 export const allowsAnyValue = (schemaLocation, ast) => {
   const schemaNode = ast[schemaLocation];
@@ -136,6 +147,7 @@ export const evaluateSchema = (schemaLocation, instance, context) => {
         throw Error(`Encountered unsupported keyword ${keywordUri}. Use the 'defineKeyword' function to add support for this keyword.`);
       }
       const keyword = keywordDefinitions[normalizedKeywordUri];
+      const outputKeywordUri = toOutputKeywordUri(keywordUri);
 
       const validationKeyword = getKeyword(keywordUri);
 
@@ -168,8 +180,8 @@ export const evaluateSchema = (schemaLocation, instance, context) => {
       }
 
       output[instanceLocation] ??= {};
-      output[instanceLocation][normalizedKeywordUri] ??= {};
-      output[instanceLocation][normalizedKeywordUri][keywordLocation] = keywordOutput
+      output[instanceLocation][outputKeywordUri] ??= {};
+      output[instanceLocation][outputKeywordUri][keywordLocation] = keywordOutput
         ? { valid: isKeywordValid, value: keywordValue, outputs: keywordOutput }
         : { valid: isKeywordValid, value: keywordValue };
 
diff --git a/src/output-plugin.js b/src/output-plugin.js
index 036ac62..83e9e80 100644
--- a/src/output-plugin.js
+++ b/src/output-plugin.js
@@ -1,4 +1,5 @@
 import * as Instance from "@hyperjump/json-schema/instance/experimental";
+import { toOutputKeywordUri } from "./json-schema-errors.js";
 
 /**
  * @import { EvaluationPlugin, Node, ValidationContext } from "@hyperjump/json-schema/experimental"
@@ -86,8 +87,9 @@ const toNormalizedOutput = ({ url, instance, valid, isBoolean, keywords }) => {
   } else if (keywords.length > 0) {
     const instanceOutput = output[Instance.uri(instance)] = Object.create(null);
     for (const { node: [keywordUri, schemaLocation, value], valid, subschemas } of keywords) {
-      instanceOutput[keywordUri] ??= Object.create(null);
-      instanceOutput[keywordUri][schemaLocation] = subschemas
+      const outputKeywordUri = toOutputKeywordUri(keywordUri);
+      instanceOutput[outputKeywordUri] ??= Object.create(null);
+      instanceOutput[outputKeywordUri][schemaLocation] = subschemas
         ? { valid, value, outputs: subschemas.map(toNormalizedOutput) }
         : { valid, value };
     }
diff --git a/src/test-suite/README.md b/src/test-suite/README.md
index 90fbe86..6882c08 100644
--- a/src/test-suite/README.md
+++ b/src/test-suite/README.md
@@ -63,3 +63,15 @@ Some of the message parameters take a list combined using "or". For example,
 parameters, you would use `{ "or": ["string", "number", "boolean"]}`. The test
 runner should combine those using an "or" appropriate for the language under
 test.
+
+## OpenAPI
+
+OpenAPI dialects use the number of the JSON Schema release they're based on:
+`4` for OpenAPI 3.0 and `2020` for OpenAPI 3.1 and 3.2. They run the tests in
+the `tests` folder and the tests in the `openapi` folder, which has tests for
+the keywords OpenAPI adds. The `openapi` folder isn't run for JSON Schema
+dialects, so in those tests, `"=4"` means OpenAPI 3.0. OpenAPI 3.0 doesn't have
+every draft-04 keyword, so the test runner skips tests with schemas that aren't
+valid OpenAPI 3.0.
+
+**Example**: `"compatibility": "=4"`
diff --git a/src/test-suite/openapi/annotations.json b/src/test-suite/openapi/annotations.json
new file mode 100644
index 0000000..efe4ab7
--- /dev/null
+++ b/src/test-suite/openapi/annotations.json
@@ -0,0 +1,41 @@
+{
+  "$schema": "../test-suite.schema.json",
+
+  "description": "The OpenAPI annotation keywords",
+  "tests": [
+    {
+      "description": "OpenAPI annotation keywords are ignored",
+      "schema": {
+        "type": "string",
+        "example": "an example",
+        "externalDocs": { "url": "https://example.com" },
+        "xml": { "name": "value" },
+        "discriminator": { "propertyName": "value" }
+      },
+      "instance": 5,
+      "errors": [
+        {
+          "messageId": "type-message",
+          "messageParams": {
+            "count": 1,
+            "type": "string",
+            "expectedTypes": { "or": ["string"] }
+          },
+          "instanceLocation": "#",
+          "schemaLocations": ["#/type"]
+        }
+      ]
+    },
+    {
+      "description": "a schema with only OpenAPI annotation keywords allows any value",
+      "schema": {
+        "example": "an example",
+        "externalDocs": { "url": "https://example.com" },
+        "xml": { "name": "value" },
+        "discriminator": { "propertyName": "value" }
+      },
+      "instance": 5,
+      "errors": []
+    }
+  ]
+}
diff --git a/src/test-suite/openapi/nullable.json b/src/test-suite/openapi/nullable.json
new file mode 100644
index 0000000..65f20eb
--- /dev/null
+++ b/src/test-suite/openapi/nullable.json
@@ -0,0 +1,38 @@
+{
+  "$schema": "../test-suite.schema.json",
+
+  "description": "The OpenAPI nullable keyword",
+  "tests": [
+    {
+      "description": "nullable expands the allowed types",
+      "compatibility": "=4",
+      "schema": {
+        "type": "string",
+        "nullable": true
+      },
+      "instance": 5,
+      "errors": [
+        {
+          "messageId": "type-message",
+          "messageParams": {
+            "count": 2,
+            "type": "null",
+            "expectedTypes": { "or": ["null", "string"] }
+          },
+          "instanceLocation": "#",
+          "schemaLocations": ["#/type"]
+        }
+      ]
+    },
+    {
+      "description": "nullable allows null",
+      "compatibility": "=4",
+      "schema": {
+        "type": "string",
+        "nullable": true
+      },
+      "instance": null,
+      "errors": []
+    }
+  ]
+}
diff --git a/src/test-suite/openapi/type.json b/src/test-suite/openapi/type.json
new file mode 100644
index 0000000..ce12cc1
--- /dev/null
+++ b/src/test-suite/openapi/type.json
@@ -0,0 +1,74 @@
+{
+  "$schema": "../test-suite.schema.json",
+
+  "description": "The OpenAPI type keyword",
+  "tests": [
+    {
+      "description": "OpenAPI type",
+      "schema": {
+        "type": "string"
+      },
+      "instance": 5,
+      "errors": [
+        {
+          "messageId": "type-message",
+          "messageParams": {
+            "count": 1,
+            "type": "string",
+            "expectedTypes": { "or": ["string"] }
+          },
+          "instanceLocation": "#",
+          "schemaLocations": ["#/type"]
+        }
+      ]
+    },
+    {
+      "description": "OpenAPI type pass",
+      "schema": {
+        "type": "string"
+      },
+      "instance": "foo",
+      "errors": []
+    },
+    {
+      "description": "anyOf drops alternatives that don't match the OpenAPI type",
+      "schema": {
+        "anyOf": [
+          { "type": "string", "minLength": 3 },
+          { "type": "number", "minimum": 10 }
+        ]
+      },
+      "instance": "a",
+      "errors": [
+        {
+          "messageId": "minLength-message",
+          "messageParams": {
+            "minLength": 3
+          },
+          "instanceLocation": "#",
+          "schemaLocations": ["#/anyOf/0/minLength"]
+        }
+      ]
+    },
+    {
+      "description": "oneOf drops alternatives that don't match the OpenAPI type",
+      "schema": {
+        "oneOf": [
+          { "type": "string", "minLength": 3 },
+          { "type": "number", "minimum": 10 }
+        ]
+      },
+      "instance": "a",
+      "errors": [
+        {
+          "messageId": "minLength-message",
+          "messageParams": {
+            "minLength": 3
+          },
+          "instanceLocation": "#",
+          "schemaLocations": ["#/oneOf/0/minLength"]
+        }
+      ]
+    }
+  ]
+}
diff --git a/src/test-suite/tests/content.json b/src/test-suite/tests/content.json
new file mode 100644
index 0000000..c3ba05b
--- /dev/null
+++ b/src/test-suite/tests/content.json
@@ -0,0 +1,61 @@
+{
+  "$schema": "../test-suite.schema.json",
+
+  "description": "The content keywords",
+  "tests": [
+    {
+      "description": "contentMediaType and contentEncoding are annotations",
+      "compatibility": "7",
+      "schema": {
+        "type": "string",
+        "contentMediaType": "application/json",
+        "contentEncoding": "base64"
+      },
+      "instance": 5,
+      "errors": [
+        {
+          "messageId": "type-message",
+          "messageParams": {
+            "count": 1,
+            "type": "string",
+            "expectedTypes": { "or": ["string"] }
+          },
+          "instanceLocation": "#",
+          "schemaLocations": ["#/type"]
+        }
+      ]
+    },
+    {
+      "description": "contentSchema is an annotation",
+      "compatibility": "2019",
+      "schema": {
+        "type": "string",
+        "contentMediaType": "application/json",
+        "contentSchema": { "type": "object" }
+      },
+      "instance": 5,
+      "errors": [
+        {
+          "messageId": "type-message",
+          "messageParams": {
+            "count": 1,
+            "type": "string",
+            "expectedTypes": { "or": ["string"] }
+          },
+          "instanceLocation": "#",
+          "schemaLocations": ["#/type"]
+        }
+      ]
+    },
+    {
+      "description": "a schema with only content keywords allows any value",
+      "compatibility": "7",
+      "schema": {
+        "contentMediaType": "application/json",
+        "contentEncoding": "base64"
+      },
+      "instance": 5,
+      "errors": []
+    }
+  ]
+}