diff --git a/quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip92IMeta/IMetaTagBuilder.kt b/quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip92IMeta/IMetaTagBuilder.kt
index de7248af7..ec1cd0cfe 100644
--- a/quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip92IMeta/IMetaTagBuilder.kt
+++ b/quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip92IMeta/IMetaTagBuilder.kt
@@ -29,7 +29,9 @@ class IMetaTagBuilder(
         key: String,
         value: String,
     ): IMetaTagBuilder {
-        properties.getOrPut(key) { mutableListOf() }.add(value)
+        val trimmed = value.trim()
+        if (trimmed.isEmpty()) return this
+        properties.getOrPut(key) { mutableListOf() }.add(trimmed)
         return this
     }
 
diff --git a/quartz/src/commonTest/kotlin/com/vitorpamplona/quartz/nip92IMeta/IMetaTagBuilderTest.kt b/quartz/src/commonTest/kotlin/com/vitorpamplona/quartz/nip92IMeta/IMetaTagBuilderTest.kt
new file mode 100644
index 000000000..3a0eff764
--- /dev/null
+++ b/quartz/src/commonTest/kotlin/com/vitorpamplona/quartz/nip92IMeta/IMetaTagBuilderTest.kt
@@ -0,0 +1,134 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * 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 com.vitorpamplona.quartz.nip92IMeta
+
+import kotlin.test.Test
+import kotlin.test.assertContentEquals
+import kotlin.test.assertEquals
+import kotlin.test.assertFalse
+import kotlin.test.assertTrue
+
+class IMetaTagBuilderTest {
+    private val sampleUrl = "https://example.com/img.jpg"
+
+    @Test
+    fun emptyValueIsSkipped() {
+        val tag =
+            IMetaTagBuilder(sampleUrl)
+                .add("x", "abc")
+                .add("alt", "")
+                .build()
+                .toTagArray()
+
+        assertFalse(tag.any { it.startsWith("alt") }, "empty alt should not appear in tag: ${tag.toList()}")
+        assertNoDanglingSpace(tag)
+    }
+
+    @Test
+    fun whitespaceOnlyValueIsSkipped() {
+        val tag =
+            IMetaTagBuilder(sampleUrl)
+                .add("x", "abc")
+                .add("alt", "   ")
+                .add("content-warning", "\t\n")
+                .build()
+                .toTagArray()
+
+        assertFalse(tag.any { it.startsWith("alt") }, "whitespace alt should not appear: ${tag.toList()}")
+        assertFalse(tag.any { it.startsWith("content-warning") }, "whitespace content-warning should not appear: ${tag.toList()}")
+        assertNoDanglingSpace(tag)
+    }
+
+    @Test
+    fun leadingAndTrailingWhitespaceIsTrimmed() {
+        val tag =
+            IMetaTagBuilder(sampleUrl)
+                .add("alt", "  hello world  ")
+                .build()
+                .toTagArray()
+
+        assertTrue(tag.contains("alt hello world"), "alt should be trimmed: ${tag.toList()}")
+        assertNoDanglingSpace(tag)
+    }
+
+    @Test
+    fun internalSpacesArePreserved() {
+        val tag =
+            IMetaTagBuilder(sampleUrl)
+                .add("alt", "a scenic photo of the coast")
+                .build()
+                .toTagArray()
+
+        assertTrue(tag.contains("alt a scenic photo of the coast"), "internal spaces preserved: ${tag.toList()}")
+    }
+
+    @Test
+    fun urlAndOneOtherFieldAreEmittedPerNip92() {
+        val tag =
+            IMetaTagBuilder(sampleUrl)
+                .add("m", "image/jpeg")
+                .build()
+                .toTagArray()
+
+        assertEquals("imeta", tag[0])
+        assertEquals("url $sampleUrl", tag[1])
+        assertContentEquals(arrayOf("imeta", "url $sampleUrl", "m image/jpeg"), tag)
+        assertNoDanglingSpace(tag)
+    }
+
+    @Test
+    fun emptyValuesProduceMinimalTag() {
+        val tag =
+            IMetaTagBuilder(sampleUrl)
+                .add("alt", "")
+                .add("content-warning", "")
+                .build()
+                .toTagArray()
+
+        assertContentEquals(arrayOf("imeta", "url $sampleUrl"), tag, "only url should remain: ${tag.toList()}")
+    }
+
+    @Test
+    fun fullImetaProducesNoDanglingSpaces() {
+        val tag =
+            IMetaTagBuilder("https://blossom.example/abc.jpg")
+                .add("x", "a27f4c02678fe5390e34580fa1b74c9e44ef161c62819bc798331599f2846d47")
+                .add("size", "168257")
+                .add("m", "image/jpeg")
+                .add("dim", "1068x1901")
+                .add("blurhash", "]LI#u#\$*~Wj[")
+                .add("ox", "a27f4c02678fe5390e34580fa1b74c9e44ef161c62819bc798331599f2846d47")
+                .add("alt", "Sample alt text")
+                .build()
+                .toTagArray()
+
+        assertNoDanglingSpace(tag)
+        tag.drop(1).forEach { entry ->
+            assertTrue(entry.contains(' '), "every entry past index 0 must be 'key SPACE value' per NIP-92: '$entry'")
+        }
+    }
+
+    private fun assertNoDanglingSpace(tag: Array<String>) {
+        tag.forEachIndexed { i, value ->
+            assertEquals(value.trim(), value, "tag[$i] has leading or trailing whitespace: '$value'")
+        }
+    }
+}