diff --git a/smack-android-extensions/build.gradle b/smack-android-extensions/build.gradle
index 2a57ed2d7..0cdad8bda 100644
--- a/smack-android-extensions/build.gradle
+++ b/smack-android-extensions/build.gradle
@@ -4,8 +4,8 @@ Extra Smack extensions for Android."""
 // Note that the test dependencies (junit, …) are inferred from the
 // sourceSet.test of the core subproject
 dependencies {
-	compile project(':smack-android')
-	compile project(':smack-extensions')
+	api project(':smack-android')
+	api project(':smack-extensions')
 
 	// Add the Android jar to the Eclipse .classpath.
 	compileClasspath files(androidBootClasspath)
diff --git a/smack-android/build.gradle b/smack-android/build.gradle
index 34b3a784a..556a526eb 100644
--- a/smack-android/build.gradle
+++ b/smack-android/build.gradle
@@ -14,13 +14,13 @@ dependencies {
 	// Android version is smaller then 21. Note that we deliberatly do
 	// not add this to smack-minidns, as this dependency may also be
 	// used in non-Android projects.
-	compile "org.minidns:minidns-android21:$miniDnsVersion"
+	implementation "org.minidns:minidns-android21:$miniDnsVersion"
 
 	// androidProjects lists all projects that are checked to compile against android.jar
 	// Filter out the optional Smack dependencies from androidProjects
 	(androidProjects - androidOptionalProjects)
 	.each { project ->
-		compile project
+		api project
 	}
 
 	// Add the Android jar to the Eclipse .classpath.
diff --git a/smack-bosh/build.gradle b/smack-bosh/build.gradle
index f686c8209..fcd3d5896 100644
--- a/smack-bosh/build.gradle
+++ b/smack-bosh/build.gradle
@@ -3,8 +3,8 @@ Smack BOSH API.
 This API is considered beta quality."""
 
 dependencies {
-	compile project(':smack-core')
+	api project(':smack-core')
 	// See https://issues.igniterealtime.org/browse/SMACK-858 and
 	// comment in version.gradle why the specify the version this way.
-	compile 'org.igniterealtime.jbosh:jbosh:[0.9.1,0.9.999]'
+	implementation 'org.igniterealtime.jbosh:jbosh:[0.9.1,0.9.999]'
 }
diff --git a/smack-core/build.gradle b/smack-core/build.gradle
index e8a75a8a5..fcc351120 100644
--- a/smack-core/build.gradle
+++ b/smack-core/build.gradle
@@ -6,10 +6,10 @@ ext {
 }
 
 dependencies {
-	compile project(':smack-xmlparser')
-	compile "org.jxmpp:jxmpp-core:$jxmppVersion"
-	compile "org.jxmpp:jxmpp-jid:$jxmppVersion"
-	compile "org.minidns:minidns-core:$miniDnsVersion"
+	api project(':smack-xmlparser')
+	api "org.jxmpp:jxmpp-core:$jxmppVersion"
+	api "org.jxmpp:jxmpp-jid:$jxmppVersion"
+	api "org.minidns:minidns-core:$miniDnsVersion"
 
 	testFixturesImplementation project(':smack-xmlparser-stax')
 	testFixturesImplementation project(':smack-xmlparser-xpp3')
diff --git a/smack-debug-slf4j/build.gradle b/smack-debug-slf4j/build.gradle
index fe3456341..9c2272729 100644
--- a/smack-debug-slf4j/build.gradle
+++ b/smack-debug-slf4j/build.gradle
@@ -4,6 +4,6 @@ Inspect the exchanged XMPP stanzas.
 Connect your favourite slf4j backend of choice to get output inside of it"""
 
 dependencies {
-    compile project(':smack-core')
-    compile 'org.slf4j:slf4j-api:[1.7,1.8)'
+    api project(':smack-core')
+    implementation 'org.slf4j:slf4j-api:[1.7,1.8)'
 }
diff --git a/smack-debug/build.gradle b/smack-debug/build.gradle
index 62324392c..959caff4f 100644
--- a/smack-debug/build.gradle
+++ b/smack-debug/build.gradle
@@ -3,5 +3,5 @@ Smack GUI debugger.
 Inspect the exchanged XMPP stanzas."""
 
 dependencies {
-	compile project(':smack-core')
+	api project(':smack-core')
 }
diff --git a/smack-experimental/build.gradle b/smack-experimental/build.gradle
index e3b2d3771..9e945e0d5 100644
--- a/smack-experimental/build.gradle
+++ b/smack-experimental/build.gradle
@@ -5,10 +5,10 @@ otherwise carefully considered for deployment. The API may change even
 between patch versions."""
 
 dependencies {
-	compile project(':smack-core')
-	compile project(':smack-extensions')
+	api project(':smack-core')
+	api project(':smack-extensions')
 
-	compile "org.hsluv:hsluv:0.2"
+	implementation "org.hsluv:hsluv:0.2"
 
 	testFixturesApi(testFixtures(project(":smack-extensions")))
 }
diff --git a/smack-extensions/build.gradle b/smack-extensions/build.gradle
index 6f56016ce..2489c9f87 100644
--- a/smack-extensions/build.gradle
+++ b/smack-extensions/build.gradle
@@ -6,10 +6,10 @@ Classes and methods that implement support for the various XMPP XEPs
 // Note that the test dependencies (junit, …) are inferred from the
 // sourceSet.test of the core subproject
 dependencies {
-	compile project(':smack-core')
+	api project(':smack-core')
 	// Some implementations need APIs provided by smack-im,
 	// e.g. message delivery receipts the roster
-	compile project(':smack-im')
+	api project(':smack-im')
 	testFixturesApi(testFixtures(project(":smack-core")))
 	//testCompile project(path: ":smack-core", configuration: "testRuntime")
 }
diff --git a/smack-im/build.gradle b/smack-im/build.gradle
index f89202c2a..f3cb2d475 100644
--- a/smack-im/build.gradle
+++ b/smack-im/build.gradle
@@ -6,6 +6,6 @@ Roster, Chat and other functionality."""
 // Note that the test dependencies (junit, …) are inferred from the
 // sourceSet.test of the core subproject
 dependencies {
-	compile project(':smack-core')
+	api project(':smack-core')
 	testImplementation(testFixtures(project(":smack-core")))
 }
diff --git a/smack-integration-test/build.gradle b/smack-integration-test/build.gradle
index 994bc851d..bf832c222 100644
--- a/smack-integration-test/build.gradle
+++ b/smack-integration-test/build.gradle
@@ -13,12 +13,12 @@ dependencies {
 	implementation "com.google.guava:guava:${guavaVersion}"
 	// Do not upgrade to a higher reflections version until
 	// https://github.com/ronmamo/reflections/issues/273 is fixed.
-	compile 'org.reflections:reflections:0.9.11'
-	compile 'eu.geekplace.javapinning:java-pinning-java7:1.1.0-alpha1'
-	compile group: 'commons-io', name: 'commons-io', version: "$commonsIoVersion"
+	implementation 'org.reflections:reflections:0.9.11'
+	api 'eu.geekplace.javapinning:java-pinning-java7:1.1.0-alpha1'
+	implementation group: 'commons-io', name: 'commons-io', version: "$commonsIoVersion"
 	api "org.junit.jupiter:junit-jupiter-api:$junitVersion"
 	testFixturesApi(testFixtures(project(":smack-core")))
-	testCompile "org.jxmpp:jxmpp-jid:$jxmppVersion:tests"
+	testImplementation "org.jxmpp:jxmpp-jid:$jxmppVersion:tests"
 }
 
 run {
diff --git a/smack-java8/build.gradle b/smack-java8/build.gradle
index 8546e7dbb..d26aa5ce3 100644
--- a/smack-java8/build.gradle
+++ b/smack-java8/build.gradle
@@ -5,9 +5,9 @@ run Smack on Java 7 (or higher) JVMs. Usually you want to add additional
 dependencies to smack-tcp, smack-extensions and smack-experimental."""
 
 dependencies {
-	compile project(":smack-core")
-	compile project(":smack-resolver-javax")
-	compile project(":smack-sasl-javax")
+	api project(":smack-core")
+	api project(":smack-resolver-javax")
+	api project(":smack-sasl-javax")
 	implementation project(":smack-xmlparser-stax")
 }
 
diff --git a/smack-jingle-old/build.gradle b/smack-jingle-old/build.gradle
index 7dff7e80e..5651864f2 100644
--- a/smack-jingle-old/build.gradle
+++ b/smack-jingle-old/build.gradle
@@ -3,8 +3,8 @@ Smack Jingle API.
 Warning: This API is beta, outdated and currenlty unmaintained."""
 
 dependencies {
-	compile project(':smack-core')
-	compile project(':smack-extensions')
-	compile 'javax.media:jmf:2.1.1e'
-	compile files('libs/jspeex-0.9.7-jfcom.jar', 'libs/jstun.jar', 'libs/Speex.jar')
+	api project(':smack-core')
+	api project(':smack-extensions')
+	api 'javax.media:jmf:2.1.1e'
+	api files('libs/jspeex-0.9.7-jfcom.jar', 'libs/jstun.jar', 'libs/Speex.jar')
 }
diff --git a/smack-legacy/build.gradle b/smack-legacy/build.gradle
index b89dbdcc8..1ecec2720 100644
--- a/smack-legacy/build.gradle
+++ b/smack-legacy/build.gradle
@@ -4,8 +4,8 @@ Usually XEPs in the state 'retracted', 'rejected', 'deprecated',
 'obsolete' or in a long standing 'deferred' state."""
 
 dependencies {
-	compile project(':smack-core')
-	compile project(':smack-extensions')
+	api project(':smack-core')
+	api project(':smack-extensions')
 
 	testFixturesApi(testFixtures(project(":smack-core")))
 }
diff --git a/smack-omemo-signal-integration-test/build.gradle b/smack-omemo-signal-integration-test/build.gradle
index f70ed0260..a499edc0c 100644
--- a/smack-omemo-signal-integration-test/build.gradle
+++ b/smack-omemo-signal-integration-test/build.gradle
@@ -7,8 +7,8 @@ mainClassName = 'org.igniterealtime.smack.inttest.smack_omemo_signal.SmackOmemoS
 applicationDefaultJvmArgs = ["-enableassertions"]
 
 dependencies {
-	compile project(':smack-integration-test')
-	compile project(':smack-omemo-signal')
+	api project(':smack-integration-test')
+	api project(':smack-omemo-signal')
 }
 
 run {
diff --git a/smack-omemo-signal/build.gradle b/smack-omemo-signal/build.gradle
index 16af5ba86..c55aa3033 100644
--- a/smack-omemo-signal/build.gradle
+++ b/smack-omemo-signal/build.gradle
@@ -3,11 +3,11 @@ Smack API for XEP-0384: OMEMO Encryption using libsignal
 """
 
 dependencies {
-	compile project(":smack-im")
-	compile project(":smack-extensions")
-	compile project(":smack-omemo")
-	compile 'org.whispersystems:signal-protocol-java:2.6.2'
+	api project(":smack-im")
+	api project(":smack-extensions")
+	api project(":smack-omemo")
+	implementation 'org.whispersystems:signal-protocol-java:2.6.2'
 
 	testFixturesApi(testFixtures(project(":smack-core")))
-	testCompile project(path: ":smack-omemo", configuration: "testRuntime")
+	testImplementation project(path: ":smack-omemo", configuration: "testRuntime")
 }
diff --git a/smack-omemo/build.gradle b/smack-omemo/build.gradle
index d1b45b005..bee2d806c 100644
--- a/smack-omemo/build.gradle
+++ b/smack-omemo/build.gradle
@@ -3,9 +3,9 @@ Smack API for XEP-0384: OMEMO Encryption
 """
 
 dependencies {
-	compile project(":smack-im")
-	compile project(":smack-extensions")
-	compile project(":smack-experimental")
+	api project(":smack-im")
+	api project(":smack-extensions")
+	api project(":smack-experimental")
 
 	testFixturesApi(testFixtures(project(":smack-core")))
 }
diff --git a/smack-openpgp/build.gradle b/smack-openpgp/build.gradle
index e083a2df6..5568f6e13 100644
--- a/smack-openpgp/build.gradle
+++ b/smack-openpgp/build.gradle
@@ -4,14 +4,14 @@ Smack API for XEP-0373: OpenPGP for XMPP."""
 // Note that the test dependencies (junit, …) are inferred from the
 // sourceSet.test of the core subproject
 dependencies {
-	compile project(':smack-core')
-	compile project(':smack-extensions')
-	compile project(':smack-experimental')
+	api project(':smack-core')
+	api project(':smack-extensions')
+	api project(':smack-experimental')
 
 	api 'org.pgpainless:pgpainless-core:0.1.0'
 
 	testImplementation "org.bouncycastle:bcprov-jdk15on:${bouncyCastleVersion}"
 
 	testFixturesApi(testFixtures(project(":smack-core")))
-	testCompile group: 'commons-io', name: 'commons-io', version: "$commonsIoVersion"
+	testImplementation group: 'commons-io', name: 'commons-io', version: "$commonsIoVersion"
 }
diff --git a/smack-repl/build.gradle b/smack-repl/build.gradle
index c1ed72fdc..739e6a1f3 100644
--- a/smack-repl/build.gradle
+++ b/smack-repl/build.gradle
@@ -19,8 +19,8 @@ dependencies {
     api project(':smack-integration-test')
     api project(':smack-omemo-signal')
 
-    compile "org.scala-lang:scala-library:$scalaVersion"
-    compile "com.lihaoyi:ammonite_$scalaVersion:1.3.2"
+    implementation "org.scala-lang:scala-library:$scalaVersion"
+    implementation "com.lihaoyi:ammonite_$scalaVersion:1.3.2"
 }
 
 scalaStyle {
diff --git a/smack-resolver-dnsjava/build.gradle b/smack-resolver-dnsjava/build.gradle
index c718abba9..b17683ecc 100644
--- a/smack-resolver-dnsjava/build.gradle
+++ b/smack-resolver-dnsjava/build.gradle
@@ -3,6 +3,6 @@ DNS SRV with dnsjava
 Use dnsjava for DNS SRV lookups."""
 
 dependencies {
-	compile project(':smack-core')
-	compile 'dnsjava:dnsjava:[3.0.0,3.0.9999]'
+	api project(':smack-core')
+	implementation 'dnsjava:dnsjava:[3.0.0,3.0.9999]'
 }
diff --git a/smack-resolver-javax/build.gradle b/smack-resolver-javax/build.gradle
index 9e67daeee..4caefb6f5 100644
--- a/smack-resolver-javax/build.gradle
+++ b/smack-resolver-javax/build.gradle
@@ -4,5 +4,5 @@ Use javax.naming for DNS SRV lookups. The javax.naming API is availabe in JavaSE
 since Java7."""
 
 dependencies {
-	compile project(':smack-core')
+	api project(':smack-core')
 }
diff --git a/smack-resolver-minidns-dox/build.gradle b/smack-resolver-minidns-dox/build.gradle
index 62c973774..de740cf84 100644
--- a/smack-resolver-minidns-dox/build.gradle
+++ b/smack-resolver-minidns-dox/build.gradle
@@ -2,6 +2,6 @@ description = """\
 DNS over XMPP (DoX) support using MiniDNS."""
 
 dependencies {
-	compile project(path: ':smack-resolver-minidns')
-	compile project(path: ':smack-experimental')
+	api project(path: ':smack-resolver-minidns')
+	api project(path: ':smack-experimental')
 }
diff --git a/smack-resolver-minidns/build.gradle b/smack-resolver-minidns/build.gradle
index 834233289..22809986c 100644
--- a/smack-resolver-minidns/build.gradle
+++ b/smack-resolver-minidns/build.gradle
@@ -4,7 +4,7 @@ Use minidns for DNS SRV lookups. For platforms that don't provide the
 javax.naming API (e.g. Android)."""
 
 dependencies {
-	compile project(':smack-core')
-	compile "org.minidns:minidns-hla:$miniDnsVersion"
-	compile "org.jxmpp:jxmpp-util-cache:$jxmppVersion"
+	api project(':smack-core')
+	api "org.minidns:minidns-hla:$miniDnsVersion"
+	implementation "org.jxmpp:jxmpp-util-cache:$jxmppVersion"
 }
diff --git a/smack-sasl-javax/build.gradle b/smack-sasl-javax/build.gradle
index f2275f363..e6fffd631 100644
--- a/smack-sasl-javax/build.gradle
+++ b/smack-sasl-javax/build.gradle
@@ -3,7 +3,7 @@ SASL with javax.security.sasl
 Use javax.security.sasl for SASL."""
 
 dependencies {
-	compile project(':smack-core')
+	api project(':smack-core')
 
 	testFixturesApi(testFixtures(project(":smack-core")))
 }
diff --git a/smack-sasl-provided/build.gradle b/smack-sasl-provided/build.gradle
index d7391664c..a9f3724d0 100644
--- a/smack-sasl-provided/build.gradle
+++ b/smack-sasl-provided/build.gradle
@@ -3,7 +3,7 @@ SASL with Smack provided code
 Use Smack provided code for SASL."""
 
 dependencies {
-	compile project(':smack-core')
+	api project(':smack-core')
 
 	testFixturesApi(testFixtures(project(":smack-core")))
 }
diff --git a/smack-tcp/build.gradle b/smack-tcp/build.gradle
index 60b4b2691..a0cffad6b 100644
--- a/smack-tcp/build.gradle
+++ b/smack-tcp/build.gradle
@@ -2,7 +2,7 @@ description = """\
 Smack for standard XMPP connections over TCP."""
 
 dependencies {
-	compile project(':smack-core')
+	api project(':smack-core')
 	api project(':smack-streammanagement')
 
 	testFixturesApi(testFixtures(project(":smack-core")))
diff --git a/smack-xmlparser-stax/build.gradle b/smack-xmlparser-stax/build.gradle
index d4e21ba8f..66cf94388 100644
--- a/smack-xmlparser-stax/build.gradle
+++ b/smack-xmlparser-stax/build.gradle
@@ -2,6 +2,6 @@ description = """\
 Smack XML parser using Stax."""
 
 dependencies {
-	compile project(':smack-xmlparser')
+	api project(':smack-xmlparser')
 	//testCompile project(path: ":smack-xmlparser", configuration: "testRuntime")
 }