diff --git a/packages/performance/src/resources/trace.test.ts b/packages/performance/src/resources/trace.test.ts
index 5931a4c955e..8bbc18218a8 100644
--- a/packages/performance/src/resources/trace.test.ts
+++ b/packages/performance/src/resources/trace.test.ts
@@ -116,10 +116,14 @@ describe('Firebase Performance > trace', () => {
 
       expect(trace.getMetric('cacheHits')).to.eql(600);
     });
+
+    it('throws error if metric doesnt exist and has invalid name', () => {
+      expect(() => trace.incrementMetric('_invalidMetric', 1)).to.throw();
+    });
   });
 
   describe('#putMetric', () => {
-    it('creates new metric if one doesnt exist.', () => {
+    it('creates new metric if one doesnt exist and has valid name.', () => {
       trace.putMetric('cacheHits', 200);
 
       expect(trace.getMetric('cacheHits')).to.eql(200);
@@ -131,6 +135,10 @@ describe('Firebase Performance > trace', () => {
 
       expect(trace.getMetric('cacheHits')).to.eql(400);
     });
+
+    it('throws error if metric doesnt exist and has invalid name', () => {
+      expect(() => trace.putMetric('_invalidMetric', 1)).to.throw();
+    });
   });
 
   describe('#getMetric', () => {
@@ -172,6 +180,19 @@ describe('Firebase Performance > trace', () => {
 
       expect(trace.getAttributes()).to.eql({ level: '7' });
     });
+
+    it('throws error if attribute name is invalid', () => {
+      expect(() => trace.putAttribute('_invalidAttribute', '1')).to.throw();
+    });
+
+    it('throws error if attribute value is invalid', () => {
+      const longAttributeValue =
+        'too-long-attribute-value-over-one-hundred-characters-too-long-attribute-value-over-one-' +
+        'hundred-charac';
+      expect(() =>
+        trace.putAttribute('validName', longAttributeValue)
+      ).to.throw();
+    });
   });
 
   describe('#getAttribute', () => {
diff --git a/packages/performance/src/resources/trace.ts b/packages/performance/src/resources/trace.ts
index b215a5492b0..f39929fe733 100644
--- a/packages/performance/src/resources/trace.ts
+++ b/packages/performance/src/resources/trace.ts
@@ -27,6 +27,11 @@ import {
 import { Api } from '../services/api_service';
 import { logTrace } from '../services/perf_logger';
 import { ERROR_FACTORY, ErrorCode } from '../utils/errors';
+import {
+  isValidCustomAttributeName,
+  isValidCustomAttributeValue
+} from '../utils/attributes_utils';
+import { isValidCustomMetricName } from '../utils/metric_utils';
 import { PerformanceTrace } from '@firebase/performance-types';
 
 const enum TraceState {
@@ -146,7 +151,7 @@ export class Trace implements PerformanceTrace {
    */
   incrementMetric(counter: string, num = 1): void {
     if (this.counters[counter] === undefined) {
-      this.counters[counter] = 0;
+      this.putMetric(counter, 0);
     }
     this.counters[counter] += num;
   }
@@ -158,7 +163,13 @@ export class Trace implements PerformanceTrace {
    * @param num Set custom metric to this value
    */
   putMetric(counter: string, num: number): void {
-    this.counters[counter] = num;
+    if (isValidCustomMetricName(counter)) {
+      this.counters[counter] = num;
+    } else {
+      throw ERROR_FACTORY.create(ErrorCode.INVALID_CUSTOM_METRIC_NAME, {
+        customMetricName: counter
+      });
+    }
   }
 
   /**
@@ -176,7 +187,23 @@ export class Trace implements PerformanceTrace {
    * @param value
    */
   putAttribute(attr: string, value: string): void {
-    this.customAttributes[attr] = value;
+    const isValidName = isValidCustomAttributeName(attr);
+    const isValidValue = isValidCustomAttributeValue(value);
+    if (isValidName && isValidValue) {
+      this.customAttributes[attr] = value;
+      return;
+    }
+    // Throw appropriate error when the attribute name or value is invalid.
+    if (!isValidName) {
+      throw ERROR_FACTORY.create(ErrorCode.INVALID_ATTRIBUTE_NAME, {
+        attributeName: attr
+      });
+    }
+    if (!isValidValue) {
+      throw ERROR_FACTORY.create(ErrorCode.INVALID_ATTRIBUTE_VALUE, {
+        attributeValue: value
+      });
+    }
   }
 
   /**
diff --git a/packages/performance/src/utils/attribute_utils.test.ts b/packages/performance/src/utils/attribute_utils.test.ts
index b08686a63dd..ddb4e6d924f 100644
--- a/packages/performance/src/utils/attribute_utils.test.ts
+++ b/packages/performance/src/utils/attribute_utils.test.ts
@@ -23,7 +23,9 @@ import {
   getVisibilityState,
   VisibilityState,
   getServiceWorkerStatus,
-  getEffectiveConnectionType
+  getEffectiveConnectionType,
+  isValidCustomAttributeName,
+  isValidCustomAttributeValue
 } from './attributes_utils';
 
 import '../../test/setup';
@@ -172,4 +174,51 @@ describe('Firebase Performance > attribute_utils', () => {
       expect(getEffectiveConnectionType()).to.be.eql(0);
     });
   });
+
+  describe('#isValidCustomAttributeName', () => {
+    it('returns true when name is valid', () => {
+      expect(isValidCustomAttributeName('validCustom_Attribute_Name')).to.be
+        .true;
+    });
+
+    it('returns false when name is blank', () => {
+      expect(isValidCustomAttributeName('')).to.be.false;
+    });
+
+    it('returns false when name is too long', () => {
+      expect(
+        isValidCustomAttributeName('invalid_custom_name_over_forty_characters')
+      ).to.be.false;
+    });
+
+    it('returns false when name starts with a reserved prefix', () => {
+      expect(isValidCustomAttributeName('firebase_invalidCustomName')).to.be
+        .false;
+    });
+
+    it('returns false when name does not begin with a letter', () => {
+      expect(isValidCustomAttributeName('_invalidCustomName')).to.be.false;
+    });
+
+    it('returns false when name contains prohibited characters', () => {
+      expect(isValidCustomAttributeName('invalidCustomName&')).to.be.false;
+    });
+  });
+
+  describe('#isValidCustomAttributeValue', () => {
+    it('returns true when value is valid', () => {
+      expect(isValidCustomAttributeValue('valid_attribute_value')).to.be.true;
+    });
+
+    it('returns false when value is blank', () => {
+      expect(isValidCustomAttributeValue('')).to.be.false;
+    });
+
+    it('returns false when value is too long', () => {
+      const longAttributeValue =
+        'too_long_attribute_value_over_one_hundred_characters_too_long_attribute_value_over_one_' +
+        'hundred_charac';
+      expect(isValidCustomAttributeValue(longAttributeValue)).to.be.false;
+    });
+  });
 });
diff --git a/packages/performance/src/utils/attributes_utils.ts b/packages/performance/src/utils/attributes_utils.ts
index dc4bb790966..98cacdba5c7 100644
--- a/packages/performance/src/utils/attributes_utils.ts
+++ b/packages/performance/src/utils/attributes_utils.ts
@@ -41,6 +41,11 @@ const enum EffectiveConnectionType {
   CONNECTION_4G = 4
 }
 
+const RESERVED_ATTRIBUTE_PREFIXES = ['firebase_', 'google_', 'ga_'];
+const ATTRIBUTE_FORMAT_REGEX = new RegExp('^[a-zA-Z]\\w*$');
+const MAX_ATTRIBUTE_NAME_LENGTH = 40;
+const MAX_ATTRIBUTE_VALUE_LENGTH = 100;
+
 export function getServiceWorkerStatus(): ServiceWorkerStatus {
   const navigator = Api.getInstance().navigator;
   if ('serviceWorker' in navigator) {
@@ -88,3 +93,17 @@ export function getEffectiveConnectionType(): EffectiveConnectionType {
       return EffectiveConnectionType.UNKNOWN;
   }
 }
+
+export function isValidCustomAttributeName(name: string): boolean {
+  if (name.length === 0 || name.length > MAX_ATTRIBUTE_NAME_LENGTH) {
+    return false;
+  }
+  const matchesReservedPrefix = RESERVED_ATTRIBUTE_PREFIXES.some(prefix =>
+    name.startsWith(prefix)
+  );
+  return !matchesReservedPrefix && !!name.match(ATTRIBUTE_FORMAT_REGEX);
+}
+
+export function isValidCustomAttributeValue(value: string): boolean {
+  return value.length !== 0 && value.length <= MAX_ATTRIBUTE_VALUE_LENGTH;
+}
diff --git a/packages/performance/src/utils/errors.ts b/packages/performance/src/utils/errors.ts
index c9ae48a60bc..15b63c0fd0b 100644
--- a/packages/performance/src/utils/errors.ts
+++ b/packages/performance/src/utils/errors.ts
@@ -27,7 +27,10 @@ export const enum ErrorCode {
   NO_API_KEY = 'no api key',
   INVALID_CC_LOG = 'invalid cc log',
   FB_NOT_DEFAULT = 'FB not default',
-  RC_NOT_OK = 'RC response not ok'
+  RC_NOT_OK = 'RC response not ok',
+  INVALID_ATTRIBUTE_NAME = 'invalid attribute name',
+  INVALID_ATTRIBUTE_VALUE = 'invalid attribute value',
+  INVALID_CUSTOM_METRIC_NAME = 'invalide custom metric name'
 }
 
 const ERROR_DESCRIPTION_MAP: { readonly [key in ErrorCode]: string } = {
@@ -40,12 +43,21 @@ const ERROR_DESCRIPTION_MAP: { readonly [key in ErrorCode]: string } = {
   [ErrorCode.INVALID_CC_LOG]: 'Attempted to queue invalid cc event',
   [ErrorCode.FB_NOT_DEFAULT]:
     'Performance can only start when Firebase app instance is the default one.',
-  [ErrorCode.RC_NOT_OK]: 'RC response is not ok'
+  [ErrorCode.RC_NOT_OK]: 'RC response is not ok',
+  [ErrorCode.INVALID_ATTRIBUTE_NAME]:
+    'Attribute name {$attributeName} is invalid.',
+  [ErrorCode.INVALID_ATTRIBUTE_VALUE]:
+    'Attribute value {$attributeValue} is invalid.',
+  [ErrorCode.INVALID_CUSTOM_METRIC_NAME]:
+    'Custom metric name {$customMetricName} is invalid'
 };
 
 interface ErrorParams {
   [ErrorCode.TRACE_STARTED_BEFORE]: { traceName: string };
   [ErrorCode.TRACE_STOPPED_BEFORE]: { traceName: string };
+  [ErrorCode.INVALID_ATTRIBUTE_NAME]: { attributeName: string };
+  [ErrorCode.INVALID_ATTRIBUTE_VALUE]: { attributeValue: string };
+  [ErrorCode.INVALID_CUSTOM_METRIC_NAME]: { customMetricName: string };
 }
 
 export const ERROR_FACTORY = new ErrorFactory<ErrorCode, ErrorParams>(
diff --git a/packages/performance/src/utils/metric_utils.test.ts b/packages/performance/src/utils/metric_utils.test.ts
new file mode 100644
index 00000000000..d19c7017cb2
--- /dev/null
+++ b/packages/performance/src/utils/metric_utils.test.ts
@@ -0,0 +1,45 @@
+/**
+ * @license
+ * Copyright 2019 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF unknown KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { expect } from 'chai';
+
+import { isValidCustomMetricName } from './metric_utils';
+
+import '../../test/setup';
+
+describe('Firebase Performance > metric_utils', () => {
+  describe('#isValidCustomMetricName', () => {
+    it('returns true when name is valid', () => {
+      expect(isValidCustomMetricName('validCustom_Metric_Name')).to.be.true;
+    });
+
+    it('returns false when name is blank', () => {
+      expect(isValidCustomMetricName('')).to.be.false;
+    });
+
+    it('returns false when name is too long', () => {
+      const longMetricName =
+        'too_long_metric_name_over_one_hundred_characters_too_long_metric_name_over_one_' +
+        'hundred_characters_too';
+      expect(isValidCustomMetricName(longMetricName)).to.be.false;
+    });
+
+    it('returns false when name starts with a reserved prefix', () => {
+      expect(isValidCustomMetricName('_invalidMetricName')).to.be.false;
+    });
+  });
+});
diff --git a/packages/performance/src/utils/metric_utils.ts b/packages/performance/src/utils/metric_utils.ts
new file mode 100644
index 00000000000..e93b4039d35
--- /dev/null
+++ b/packages/performance/src/utils/metric_utils.ts
@@ -0,0 +1,26 @@
+/**
+ * @license
+ * Copyright 2019 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+const MAX_METRIC_NAME_LENGTH = 100;
+const RESERVED_AUTO_PREFIX = '_';
+
+export function isValidCustomMetricName(name: string): boolean {
+  if (name.length === 0 || name.length > MAX_METRIC_NAME_LENGTH) {
+    return false;
+  }
+  return !name.startsWith(RESERVED_AUTO_PREFIX);
+}
diff --git a/packages/polyfill/index.ts b/packages/polyfill/index.ts
index b3c714f4582..6c59e501078 100644
--- a/packages/polyfill/index.ts
+++ b/packages/polyfill/index.ts
@@ -25,6 +25,7 @@ import 'promise-polyfill/lib/polyfill';
 import 'core-js/features/array/find';
 import 'core-js/features/array/find-index';
 import 'core-js/features/array/from';
+import 'core-js/features/array/some';
 import 'core-js/features/object/assign';
 import 'core-js/features/object/entries';
 import 'core-js/features/object/values';