diff --git a/core/pom.xml b/core/pom.xml
index 76f027e1..64a141e4 100644
--- a/core/pom.xml
+++ b/core/pom.xml
@@ -126,6 +126,7 @@
                                         <!--inculde>**/tests/draft2020-12/ref.json</inculde-->
                                         <inculde>**/tests/draft2020-12/required.json</inculde>
                                         <inculde>**/tests/draft2020-12/type.json</inculde>
+                                        <inculde>**/tests/draft2020-12/uniqueItems.json</inculde>
                                     </includes>
                                 </resource>
                             </resources>
diff --git a/core/src/main/java/io/github/sebastiantoepfer/jsonschema/core/vocab/validation/UniqueItemsKeywordType.java b/core/src/main/java/io/github/sebastiantoepfer/jsonschema/core/vocab/validation/UniqueItemsKeywordType.java
new file mode 100644
index 00000000..c2747423
--- /dev/null
+++ b/core/src/main/java/io/github/sebastiantoepfer/jsonschema/core/vocab/validation/UniqueItemsKeywordType.java
@@ -0,0 +1,146 @@
+/*
+ * The MIT License
+ *
+ * Copyright 2023 sebastian.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package io.github.sebastiantoepfer.jsonschema.core.vocab.validation;
+
+import io.github.sebastiantoepfer.jsonschema.InstanceType;
+import io.github.sebastiantoepfer.jsonschema.JsonSchema;
+import io.github.sebastiantoepfer.jsonschema.keyword.Assertion;
+import io.github.sebastiantoepfer.jsonschema.keyword.Keyword;
+import io.github.sebastiantoepfer.jsonschema.keyword.KeywordType;
+import jakarta.json.JsonArray;
+import jakarta.json.JsonNumber;
+import jakarta.json.JsonValue;
+import jakarta.json.JsonValue.ValueType;
+import java.math.BigDecimal;
+import java.util.HashSet;
+import java.util.Objects;
+import java.util.Set;
+
+final class UniqueItemsKeywordType implements KeywordType {
+
+    @Override
+    public String name() {
+        return "uniqueItems";
+    }
+
+    @Override
+    public Keyword createKeyword(final JsonSchema schema, final JsonValue value) {
+        if (InstanceType.BOOLEAN.isInstance(value)) {
+            return new UniqueItemsKeyword(value.getValueType() == JsonValue.ValueType.TRUE);
+        } else {
+            throw new IllegalArgumentException("Value must be a boolean!");
+        }
+    }
+
+    private class UniqueItemsKeyword implements Assertion {
+
+        private final boolean unique;
+
+        private UniqueItemsKeyword(final boolean unique) {
+            this.unique = unique;
+        }
+
+        @Override
+        public boolean isValidFor(final JsonValue instance) {
+            return (
+                !InstanceType.ARRAY.isInstance(instance) ||
+                !unique ||
+                new JsonArrayChecks(instance.asJsonArray()).areAllElementsUnique()
+            );
+        }
+
+        @Override
+        public boolean hasName(final String name) {
+            return Objects.equals(name(), name);
+        }
+
+        private static class JsonArrayChecks {
+
+            private final JsonArray values;
+
+            public JsonArrayChecks(final JsonArray values) {
+                this.values = Objects.requireNonNull(values);
+            }
+
+            public boolean areAllElementsUnique() {
+                final Set<JsonValueNumberEqualsFix> uniqueValues = new HashSet<>();
+                return values.stream().map(JsonValueNumberEqualsFix::new).allMatch(uniqueValues::add);
+            }
+        }
+    }
+
+    /*
+    bad class name :( ->
+    we must override equals for numbers. 1.0 and 1.00 must be equals.
+    but neither new BigDecimal("1.0").equals(new BigDecimal("1.00")
+    nor Json.create(new BigDecimal("1.0")).equals(Json.create(new BigDecimal("1.00"))
+    are.
+     */
+    static class JsonValueNumberEqualsFix {
+
+        private final JsonValue value;
+
+        public JsonValueNumberEqualsFix(final JsonValue value) {
+            this.value = value;
+        }
+
+        @Override
+        public int hashCode() {
+            final int result;
+            if (isNumber()) {
+                result = normalizeValue().hashCode();
+            } else {
+                result = value.hashCode();
+            }
+            return result;
+        }
+
+        @Override
+        public boolean equals(final Object obj) {
+            return (
+                this == obj || (obj != null && getClass() == obj.getClass() && equals((JsonValueNumberEqualsFix) obj))
+            );
+        }
+
+        private boolean equals(final JsonValueNumberEqualsFix other) {
+            final boolean result;
+            if (isNumber() && other.isNumber()) {
+                result = normalizeValue().equals(other.normalizeValue());
+            } else if (isNumber()) {
+                result = false;
+            } else {
+                result = value.equals(other.value);
+            }
+            return result;
+        }
+
+        private BigDecimal normalizeValue() {
+            return ((JsonNumber) value).bigDecimalValue().stripTrailingZeros();
+        }
+
+        private boolean isNumber() {
+            return value.getValueType() == ValueType.NUMBER;
+        }
+    }
+}
diff --git a/core/src/main/java/io/github/sebastiantoepfer/jsonschema/core/vocab/validation/ValidationVocabulary.java b/core/src/main/java/io/github/sebastiantoepfer/jsonschema/core/vocab/validation/ValidationVocabulary.java
index 26e27f56..55a70772 100644
--- a/core/src/main/java/io/github/sebastiantoepfer/jsonschema/core/vocab/validation/ValidationVocabulary.java
+++ b/core/src/main/java/io/github/sebastiantoepfer/jsonschema/core/vocab/validation/ValidationVocabulary.java
@@ -49,7 +49,8 @@ public ValidationVocabulary() {
                 new ExclusiveMaximumKeywordType(),
                 new MultipleOfKeywordType(),
                 new MinItemsKeywordType(),
-                new MaxItemsKeywordType()
+                new MaxItemsKeywordType(),
+                new UniqueItemsKeywordType()
             );
     }
 
diff --git a/core/src/test/java/io/github/sebastiantoepfer/jsonschema/core/vocab/validation/MaxLengthKeywordTypeTest.java b/core/src/test/java/io/github/sebastiantoepfer/jsonschema/core/vocab/validation/MaxLengthKeywordTypeTest.java
index db537124..34ca837a 100644
--- a/core/src/test/java/io/github/sebastiantoepfer/jsonschema/core/vocab/validation/MaxLengthKeywordTypeTest.java
+++ b/core/src/test/java/io/github/sebastiantoepfer/jsonschema/core/vocab/validation/MaxLengthKeywordTypeTest.java
@@ -29,8 +29,6 @@
 
 import io.github.sebastiantoepfer.jsonschema.JsonSchema;
 import io.github.sebastiantoepfer.jsonschema.core.DefaultJsonSchemaFactory;
-import io.github.sebastiantoepfer.jsonschema.core.vocab.validation.MaxLengthKeywordType;
-import io.github.sebastiantoepfer.jsonschema.core.vocab.validation.MinLengthKeywordType;
 import io.github.sebastiantoepfer.jsonschema.keyword.Keyword;
 import jakarta.json.Json;
 import jakarta.json.JsonNumber;
diff --git a/core/src/test/java/io/github/sebastiantoepfer/jsonschema/core/vocab/validation/UniqueItemsKeywordTypeTest.java b/core/src/test/java/io/github/sebastiantoepfer/jsonschema/core/vocab/validation/UniqueItemsKeywordTypeTest.java
new file mode 100644
index 00000000..405f2945
--- /dev/null
+++ b/core/src/test/java/io/github/sebastiantoepfer/jsonschema/core/vocab/validation/UniqueItemsKeywordTypeTest.java
@@ -0,0 +1,134 @@
+/*
+ * The MIT License
+ *
+ * Copyright 2023 sebastian.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package io.github.sebastiantoepfer.jsonschema.core.vocab.validation;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.is;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import io.github.sebastiantoepfer.jsonschema.JsonSchema;
+import io.github.sebastiantoepfer.jsonschema.core.DefaultJsonSchemaFactory;
+import io.github.sebastiantoepfer.jsonschema.keyword.Keyword;
+import io.github.sebastiantoepfer.jsonschema.keyword.KeywordType;
+import jakarta.json.Json;
+import jakarta.json.JsonValue;
+import java.io.StringReader;
+import java.math.BigDecimal;
+import org.junit.jupiter.api.Test;
+
+class UniqueItemsKeywordTypeTest {
+
+    @Test
+    void should_know_his_name() {
+        final Keyword keyword = new UniqueItemsKeywordType()
+            .createKeyword(new DefaultJsonSchemaFactory().create(JsonValue.TRUE), JsonValue.FALSE);
+
+        assertThat(keyword.hasName("uniqueItems"), is(true));
+        assertThat(keyword.hasName("test"), is(false));
+    }
+
+    @Test
+    void should_not_be_createbale_from_non_boolean() {
+        final JsonSchema schema = new DefaultJsonSchemaFactory().create(JsonValue.TRUE);
+        final KeywordType keywordType = new UniqueItemsKeywordType();
+        assertThrows(
+            IllegalArgumentException.class,
+            () -> keywordType.createKeyword(schema, JsonValue.EMPTY_JSON_OBJECT)
+        );
+    }
+
+    @Test
+    void should_be_valid_for_uniqueItems() {
+        assertThat(
+            new UniqueItemsKeywordType()
+                .createKeyword(new DefaultJsonSchemaFactory().create(JsonValue.TRUE), JsonValue.TRUE)
+                .asAssertion()
+                .isValidFor(Json.createArrayBuilder().add("1").add("2").build()),
+            is(true)
+        );
+    }
+
+    @Test
+    void should_be_valid_for_non_uniqueItems_if_false() {
+        assertThat(
+            new UniqueItemsKeywordType()
+                .createKeyword(new DefaultJsonSchemaFactory().create(JsonValue.TRUE), JsonValue.FALSE)
+                .asAssertion()
+                .isValidFor(Json.createArrayBuilder().add("1").add("1").build()),
+            is(true)
+        );
+    }
+
+    @Test
+    void should_be_invalid_for_non_uniqueItems() {
+        assertThat(
+            new UniqueItemsKeywordType()
+                .createKeyword(new DefaultJsonSchemaFactory().create(JsonValue.TRUE), JsonValue.TRUE)
+                .asAssertion()
+                .isValidFor(Json.createArrayBuilder().add("1").add("1").build()),
+            is(false)
+        );
+    }
+
+    @Test
+    void should_be_valid_for_non_arrays() {
+        assertThat(
+            new UniqueItemsKeywordType()
+                .createKeyword(new DefaultJsonSchemaFactory().create(JsonValue.TRUE), JsonValue.FALSE)
+                .asAssertion()
+                .isValidFor(JsonValue.EMPTY_JSON_OBJECT),
+            is(true)
+        );
+    }
+
+    @Test
+    void should_be_invalid_if_numbers_mathematically_unequal() {
+        assertThat(
+            new UniqueItemsKeywordType()
+                .createKeyword(new DefaultJsonSchemaFactory().create(JsonValue.TRUE), JsonValue.TRUE)
+                .asAssertion()
+                .isValidFor(Json.createReader(new StringReader("[1.0,1.00,1]")).readArray()),
+            is(false)
+        );
+    }
+
+    @Test
+    void pitests_say_i_must_write_this_tests() {
+        //hashset uses hashCode to determine if equals needs to be used, so we don't really need equals.
+        //but to have a valid java class we should override both
+        final UniqueItemsKeywordType.JsonValueNumberEqualsFix obj = new UniqueItemsKeywordType.JsonValueNumberEqualsFix(
+            JsonValue.EMPTY_JSON_OBJECT
+        );
+        final UniqueItemsKeywordType.JsonValueNumberEqualsFix number1 =
+            new UniqueItemsKeywordType.JsonValueNumberEqualsFix(Json.createValue(new BigDecimal("1.0")));
+        final UniqueItemsKeywordType.JsonValueNumberEqualsFix number2 =
+            new UniqueItemsKeywordType.JsonValueNumberEqualsFix(Json.createValue(new BigDecimal("1.00")));
+
+        assertThat(obj.equals(obj), is(true));
+        assertThat(number1.equals(number1), is(true));
+        assertThat(number1.equals(number2), is(true));
+
+        assertThat(obj.equals(number1), is(false));
+    }
+}