diff --git a/Source/Core/EdgeAPI.swift b/Source/Core/EdgeAPI.swift
index 5e61c85..f5f35e9 100644
--- a/Source/Core/EdgeAPI.swift
+++ b/Source/Core/EdgeAPI.swift
@@ -81,7 +81,8 @@ final class EdgeAPI: Sendable {
             .compactMap({ URLQueryItem(name: "id", value: $0) })
         
         let hidQueryItems = hids
-            .compactMap({ $0.extendedIdentifier })
+            .map({ $0.extendedIdentifier })
+            .filter({ $0.isEmpty == false })
             .compactMap({ URLQueryItem(name: "hid", value: $0) })
 
         queryItems.append(contentsOf: hidQueryItems)
diff --git a/Source/Core/OptableIdentifierEncoder.swift b/Source/Core/OptableIdentifierEncoder.swift
index 8a65694..8aa0ab9 100644
--- a/Source/Core/OptableIdentifierEncoder.swift
+++ b/Source/Core/OptableIdentifierEncoder.swift
@@ -31,6 +31,9 @@ enum OptableIdentifierEncoder {
         case let .hem(value): hem(prefix, value)
         case let .hashedPhoneNumber(value): hashedPhoneNumber(prefix, value)
         }
+
+        // An identifier whose value is empty once normalized is dropped rather than sent as "prefix:"
+        guard let separator = eid.firstIndex(of: ":"), eid.index(after: separator) < eid.endIndex else { return "" }
         return eid
     }
 
@@ -50,16 +53,20 @@ enum OptableIdentifierEncoder {
     }
 
     /// Builds Extended Identifier from Email address
+    /// Returns an empty string when nothing is left to hash, so the SHA256 of an empty string is never sent.
     static func email(_ prefix: String, _ email: String) -> String {
-        let normalizedData = Data(email.components(separatedBy: CharacterSet.whitespacesAndNewlines).joined().lowercased().utf8)
-        let identifier = sha256(data: normalizedData)
+        let normalized = email.components(separatedBy: CharacterSet.whitespacesAndNewlines).joined().lowercased()
+        guard normalized.isEmpty == false else { return "" }
+        let identifier = sha256(data: Data(normalized.utf8))
         return "\(prefix):\(identifier)"
     }
 
     /// Builds Extended Identifier from Phone number
+    /// Returns an empty string when nothing is left to hash, so the SHA256 of an empty string is never sent.
     static func phoneNumber(_ prefix: String, _ phoneNumber: String) -> String {
-        let normalizedData = Data(phoneNumber.components(separatedBy: CharacterSet.whitespacesAndNewlines).joined().lowercased().utf8)
-        let identifier = sha256(data: normalizedData)
+        let normalized = phoneNumber.components(separatedBy: CharacterSet.whitespacesAndNewlines).joined().lowercased()
+        guard normalized.isEmpty == false else { return "" }
+        let identifier = sha256(data: Data(normalized.utf8))
         return "\(prefix):\(identifier)"
     }
 
diff --git a/Tests/Unit/EdgeAPITests.swift b/Tests/Unit/EdgeAPITests.swift
index 0894270..bace3e6 100644
--- a/Tests/Unit/EdgeAPITests.swift
+++ b/Tests/Unit/EdgeAPITests.swift
@@ -368,6 +368,16 @@ class EdgeAPITests: XCTestCase {
     /**
      For more info check: [](https://docs.optable.co/optable-documentation/guides/real-time-api-integrations-guide/optable-real-time-api-endpoints/profile)
      */
+    func test_targeting_request_drops_blank_identifiers() throws {
+        let postalCode: OptableIdentifier = .postalCode("H2X 1Y4")
+        let blank: OptableIdentifier = .postalCode("   ")
+        let urlRequest = try sdk.api.targeting(ids: [postalCode, blank], hids: [postalCode, blank])
+        let queryItems = URLComponents(url: urlRequest!.url!, resolvingAgainstBaseURL: false)!.queryItems ?? []
+
+        XCTAssertEqual(queryItems.filter({ $0.name == "id" }).map(\.value), [postalCode.extendedIdentifier])
+        XCTAssertEqual(queryItems.filter({ $0.name == "hid" }).map(\.value), [postalCode.extendedIdentifier])
+    }
+
     func test_profile_request_generation() throws {
         let urlRequest = try sdk.api.profile(traits: ["test-key": "test-value"], id: "c:id2", neighbors: ["c:id1", "c:id3"])
         
diff --git a/Tests/Unit/OptableIdentifierEncoderTests.swift b/Tests/Unit/OptableIdentifierEncoderTests.swift
index ea44ed1..5a59ff0 100644
--- a/Tests/Unit/OptableIdentifierEncoderTests.swift
+++ b/Tests/Unit/OptableIdentifierEncoderTests.swift
@@ -142,6 +142,27 @@ class OptableIdentifierEncoderTests: XCTestCase {
         XCTAssertNotEqual(unexpected, SUT.custom(prefix, "foobarBAZ-01234#98765.!!!"))
     }
 
+    func test_emptyAfterNormalization_isDropped() {
+        let blank = "  \n "
+        let identifiers: [OptableIdentifier] = [
+            .emailAddress(blank), .phoneNumber(blank), .postalCode(blank),
+            .ipv4Address(blank), .ipv6Address(blank),
+            .appleIDFA(blank), .googleGAID(blank), .rokuRIDA(blank), .samsungTIFA(blank), .amazonFireAFAI(blank),
+            .netID(blank), .id5(blank), .utiq(blank),
+            .custom(nil, blank), .custom(2, blank), .optableVID(blank),
+            .hem(blank), .hashedPhoneNumber(blank),
+        ]
+
+        for identifier in identifiers {
+            XCTAssertEqual("", identifier.extendedIdentifier, "\(identifier) should be dropped")
+        }
+    }
+
+    func test_email_and_phoneNumber_neverSendTheHashOfAnEmptyString() {
+        XCTAssertEqual("", SUT.email("e", ""))
+        XCTAssertEqual("", SUT.phoneNumber("p", " "))
+    }
+
     func test_hem() {
         let prefix = OptableIdentifier.hem("").prefix
         let hem = "a665a45920422f9d417e4867efdc4fb8a04a1f3fff1fa07e998e86f7f7a27ae3"
diff --git a/Tests/Unit/OptableIdentifiersTests.swift b/Tests/Unit/OptableIdentifiersTests.swift
index a839baf..73d0fa2 100644
--- a/Tests/Unit/OptableIdentifiersTests.swift
+++ b/Tests/Unit/OptableIdentifiersTests.swift
@@ -27,7 +27,7 @@ class OptableIdentifiersTests: XCTestCase {
             .id5("ID5*UDWnp3JOtWV0ky-bHvEeU4xOVHXCmYeg24YigF8iAymUHplfYSElM3fy79h8p-Fg"),
             .utiq("496f5db5-681f-4392-acd5-0d4f6e2f6b88"),
             .custom(nil, "d29c551097b9dd0b82423827f65161232efaf7fc"),
-            .custom(2, ""),
+            .custom(2, "two"),
             .custom(1, "AaaZza.dh012"),
             .custom(1, "another c1"),
         ]
@@ -52,7 +52,7 @@ class OptableIdentifiersTests: XCTestCase {
         XCTAssertTrue(decodedData.contains(where: { $0 == "f:6e853799-ef31-4a30-8706-9742be254d38" }))
         XCTAssertTrue(decodedData.contains(where: { $0 == "n:_YV2v2Uhx3vqeH47Rrhzgr-4c3VNsxis4M1WY9qn--QTbVapax5VM2HJykoGAyWcwS5lKQ" }))
         XCTAssertTrue(decodedData.contains(where: { $0 == "c:d29c551097b9dd0b82423827f65161232efaf7fc" }))
-        XCTAssertTrue(decodedData.contains(where: { $0 == "c2:" }))
+        XCTAssertTrue(decodedData.contains(where: { $0 == "c2:two" }))
         XCTAssertTrue(decodedData.contains(where: { $0 == "c1:AaaZza.dh012" }))
 
         // Test multiple similar ids existance ( double c1 )
@@ -62,7 +62,7 @@ class OptableIdentifiersTests: XCTestCase {
 
         let c_Idx = try XCTUnwrap(decodedData.firstIndex(of: "c:d29c551097b9dd0b82423827f65161232efaf7fc"))
         let c1_Idx = try XCTUnwrap(decodedData.firstIndex(of: "c1:AaaZza.dh012"))
-        let c2_Idx = try XCTUnwrap(decodedData.firstIndex(of: "c2:"))
+        let c2_Idx = try XCTUnwrap(decodedData.firstIndex(of: "c2:two"))
 
         XCTAssert(c_Idx < c2_Idx)
         XCTAssert(c2_Idx < c1_Idx)