diff --git a/src/Packages/Audience/Runtime/Events/MessageBuilder.cs b/src/Packages/Audience/Runtime/Events/MessageBuilder.cs
new file mode 100644
index 000000000..efc3ec396
--- /dev/null
+++ b/src/Packages/Audience/Runtime/Events/MessageBuilder.cs
@@ -0,0 +1,92 @@
+using System;
+using System.Collections.Generic;
+
+namespace Immutable.Audience
+{
+    internal static class MessageBuilder
+    {
+        internal static Dictionary<string, object> Track(
+            string eventName,
+            string anonymousId,
+            string userId,
+            string packageVersion,
+            Dictionary<string, object> properties = null)
+        {
+            var msg = BuildBase("track", packageVersion);
+            msg["eventName"] = Truncate(eventName, 256);
+
+            if (!string.IsNullOrEmpty(anonymousId))
+                msg["anonymousId"] = Truncate(anonymousId, 256);
+
+            if (!string.IsNullOrEmpty(userId))
+                msg["userId"] = Truncate(userId, 256);
+
+            if (properties != null && properties.Count > 0)
+                msg["properties"] = properties;
+
+            return msg;
+        }
+
+        internal static Dictionary<string, object> Identify(
+            string anonymousId,
+            string userId,
+            string identityType,
+            string packageVersion,
+            Dictionary<string, object> traits = null)
+        {
+            var msg = BuildBase("identify", packageVersion);
+
+            if (!string.IsNullOrEmpty(anonymousId))
+                msg["anonymousId"] = Truncate(anonymousId, 256);
+
+            if (!string.IsNullOrEmpty(userId))
+                msg["userId"] = Truncate(userId, 256);
+
+            if (!string.IsNullOrEmpty(identityType))
+                msg["identityType"] = Truncate(identityType, 256);
+
+            if (traits != null && traits.Count > 0)
+                msg["traits"] = traits;
+
+            return msg;
+        }
+
+        internal static Dictionary<string, object> Alias(
+            string fromId,
+            string fromType,
+            string toId,
+            string toType,
+            string packageVersion)
+        {
+            var msg = BuildBase("alias", packageVersion);
+            msg["fromId"] = Truncate(fromId, 256);
+            msg["fromType"] = Truncate(fromType, 256);
+            msg["toId"] = Truncate(toId, 256);
+            msg["toType"] = Truncate(toType, 256);
+            return msg;
+        }
+
+        private static Dictionary<string, object> BuildBase(string type, string packageVersion)
+        {
+            return new Dictionary<string, object>
+            {
+                ["type"] = type,
+                ["messageId"] = Guid.NewGuid().ToString(),
+                ["eventTimestamp"] = DateTime.UtcNow.ToString("o"),
+                ["context"] = new Dictionary<string, object>
+                {
+                    ["library"] = Constants.LibraryName,
+                    ["libraryVersion"] = Truncate(packageVersion, 256)
+                },
+                ["surface"] = Constants.Surface
+            };
+        }
+
+        private static string Truncate(string s, int maxLen)
+        {
+            if (s == null || s.Length <= maxLen)
+                return s;
+            return s.Substring(0, maxLen);
+        }
+    }
+}
diff --git a/src/Packages/Audience/Tests/Runtime/MessageBuilderTests.cs b/src/Packages/Audience/Tests/Runtime/MessageBuilderTests.cs
new file mode 100644
index 000000000..bd3aad3cc
--- /dev/null
+++ b/src/Packages/Audience/Tests/Runtime/MessageBuilderTests.cs
@@ -0,0 +1,101 @@
+using System.Collections.Generic;
+using NUnit.Framework;
+
+namespace Immutable.Audience.Tests
+{
+    [TestFixture]
+    public class MessageBuilderTests
+    {
+        private const string PackageVersion = "1.2.3";
+
+        [Test]
+        public void Track_RequiredFieldsPresent()
+        {
+            var result = MessageBuilder.Track("level_complete", "anon-1", null, PackageVersion);
+
+            Assert.AreEqual("track", result["type"]);
+            Assert.IsTrue(result.ContainsKey("messageId"));
+            Assert.IsTrue(result.ContainsKey("eventTimestamp"));
+            Assert.IsTrue(result.ContainsKey("context"));
+            Assert.IsTrue(result.ContainsKey("surface"));
+            Assert.AreEqual("level_complete", result["eventName"]);
+        }
+
+        [Test]
+        public void Track_EventNameLongerThan256Chars_TruncatedTo256()
+        {
+            var longName = new string('x', 300);
+
+            var result = MessageBuilder.Track(longName, null, null, PackageVersion);
+
+            Assert.AreEqual(256, ((string)result["eventName"]).Length);
+        }
+
+        [Test]
+        public void Track_NullUserId_NotPresentInDict()
+        {
+            var result = MessageBuilder.Track("evt", "anon-1", null, PackageVersion);
+
+            Assert.IsFalse(result.ContainsKey("userId"));
+        }
+
+        [Test]
+        public void Track_NonNullUserId_PresentInDict()
+        {
+            var result = MessageBuilder.Track("evt", "anon-1", "user-99", PackageVersion);
+
+            Assert.IsTrue(result.ContainsKey("userId"));
+            Assert.AreEqual("user-99", result["userId"]);
+        }
+
+        [Test]
+        public void Identify_TypeAndIdentityFieldsPresent()
+        {
+            var result = MessageBuilder.Identify("anon-42", "user-42", "steam", PackageVersion);
+
+            Assert.AreEqual("identify", result["type"]);
+            Assert.AreEqual("anon-42", result["anonymousId"]);
+            Assert.AreEqual("user-42", result["userId"]);
+            Assert.AreEqual("steam", result["identityType"]);
+        }
+
+        [Test]
+        public void Alias_AllFourFieldsPresent()
+        {
+            var result = MessageBuilder.Alias("from-id", "email", "to-id", "steam", PackageVersion);
+
+            Assert.AreEqual("alias", result["type"]);
+            Assert.AreEqual("from-id", result["fromId"]);
+            Assert.AreEqual("email", result["fromType"]);
+            Assert.AreEqual("to-id", result["toId"]);
+            Assert.AreEqual("steam", result["toType"]);
+        }
+
+        [Test]
+        public void AllMessages_ContextContainsLibraryAndLibraryVersion()
+        {
+            var track = MessageBuilder.Track("evt", null, null, PackageVersion);
+            var identify = MessageBuilder.Identify(null, "u1", null, PackageVersion);
+            var alias = MessageBuilder.Alias("f", "t1", "t", "t2", PackageVersion);
+
+            foreach (var msg in new[] { track, identify, alias })
+            {
+                var ctx = (Dictionary<string, object>)msg["context"];
+                Assert.AreEqual(Constants.LibraryName, ctx["library"]);
+                Assert.AreEqual(PackageVersion, ctx["libraryVersion"]);
+            }
+        }
+
+        [Test]
+        public void AllMessages_SurfaceIsUnity()
+        {
+            var track = MessageBuilder.Track("evt", null, null, PackageVersion);
+            var identify = MessageBuilder.Identify(null, "u1", null, PackageVersion);
+            var alias = MessageBuilder.Alias("f", "t1", "t", "t2", PackageVersion);
+
+            Assert.AreEqual("unity", track["surface"]);
+            Assert.AreEqual("unity", identify["surface"]);
+            Assert.AreEqual("unity", alias["surface"]);
+        }
+    }
+}