diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index f23c2af20..3731589e3 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -24,6 +24,13 @@ repos:
 
 - repo: local
   hooks:
+  - id: license
+    name: Spotless
+    files: ".*\\.(java|kt|kts)$"
+    language: system
+    entry: ./gradlew spotlessApply
+    pass_filenames: false
+    require_serial: true
   - id: checkstyle
     name: Check Java codestyle
     files: ".*\\.java$"
@@ -31,18 +38,11 @@ repos:
     entry: ./gradlew checkstyleMain checkstyleTest
     pass_filenames: false
     require_serial: true
-  - id: license
-    name: Check Java license headers
-    files: ".*\\.java$"
-    language: system
-    entry: ./gradlew licenseFormat
-    pass_filenames: false
-    require_serial: true
   - id: illuaminate
     name: Check Lua code
     files: ".*\\.(lua|java|md)"
     language: system
-    entry: ./gradlew lintLua -i
+    entry: ./gradlew lintLua
     pass_filenames: false
     require_serial: true
 
diff --git a/build.gradle b/build.gradle
index 6b248a47d..8559c9150 100644
--- a/build.gradle
+++ b/build.gradle
@@ -2,7 +2,6 @@ plugins {
     id "checkstyle"
     id "jacoco"
     id "maven-publish"
-    id "org.cadixdev.licenser" version "0.6.1"
     id "com.matthewprenger.cursegradle" version "1.4.0"
     id "com.github.breadmoirai.github-release" version "2.2.12"
     id "org.jetbrains.kotlin.jvm" version "1.7.0"
@@ -11,7 +10,8 @@ plugins {
     id "org.spongepowered.mixin" version "0.7.+"
     id "org.parchmentmc.librarian.forgegradle" version "1.+"
     id "com.github.johnrengelman.shadow" version "7.1.2"
-    id "cc-tweaked.illuaminate"
+    id("cc-tweaked.illuaminate")
+    id("cc-tweaked.java-convention")
 }
 
 
@@ -388,23 +388,6 @@ jacocoTestReport {
 
 test.finalizedBy("jacocoTestReport")
 
-license {
-    header = file('config/license/main.txt')
-    lineEnding = '\n'
-    newLine = false
-
-    properties {
-        year = Calendar.getInstance().get(Calendar.YEAR)
-    }
-
-    include("**/*.java") // We could apply to Kotlin, but for now let's not
-    matching("dan200/computercraft/api/**") {
-        header = file('config/license/api.txt')
-    }
-}
-
-check.dependsOn("licenseCheck")
-
 def lintLua = tasks.register("lintLua", IlluaminateExec.class) {
     group = JavaBasePlugin.VERIFICATION_GROUP
     description = "Lint Lua (and Lua docs) with illuaminate"
diff --git a/buildSrc/build.gradle.kts b/buildSrc/build.gradle.kts
index fc582ed5b..c71bab99a 100644
--- a/buildSrc/build.gradle.kts
+++ b/buildSrc/build.gradle.kts
@@ -8,6 +8,10 @@ repositories {
     gradlePluginPortal()
 }
 
+dependencies {
+    implementation(libs.spotless)
+}
+
 gradlePlugin {
     plugins {
         register("cc-tweaked.illuaminate") {
diff --git a/buildSrc/settings.gradle.kts b/buildSrc/settings.gradle.kts
new file mode 100644
index 000000000..b5a0fabf6
--- /dev/null
+++ b/buildSrc/settings.gradle.kts
@@ -0,0 +1,7 @@
+dependencyResolutionManagement {
+    versionCatalogs {
+        create("libs") {
+            from(files("../gradle/libs.versions.toml"))
+        }
+    }
+}
diff --git a/buildSrc/src/main/kotlin/cc-tweaked.java-convention.gradle.kts b/buildSrc/src/main/kotlin/cc-tweaked.java-convention.gradle.kts
new file mode 100644
index 000000000..ca2ac0a90
--- /dev/null
+++ b/buildSrc/src/main/kotlin/cc-tweaked.java-convention.gradle.kts
@@ -0,0 +1,48 @@
+import cc.tweaked.gradle.LicenseHeader
+import com.diffplug.gradle.spotless.FormatExtension
+import com.diffplug.spotless.LineEnding
+import java.nio.charset.StandardCharsets
+
+plugins {
+    java
+    jacoco
+    id("com.diffplug.spotless")
+}
+
+spotless {
+    encoding = StandardCharsets.UTF_8
+    lineEndings = LineEnding.UNIX
+
+    fun FormatExtension.defaults() {
+        endWithNewline()
+        trimTrailingWhitespace()
+        indentWithSpaces(4)
+    }
+
+    val licenser = LicenseHeader.create(
+        api = file("config/license/api.txt"),
+        main = file("config/license/main.txt"),
+    )
+
+    java {
+        defaults()
+        addStep(licenser)
+        removeUnusedImports()
+    }
+
+    val ktlintConfig = mapOf(
+        "disabled_rules" to "no-wildcard-imports",
+        "ij_kotlin_allow_trailing_comma" to "true",
+        "ij_kotlin_allow_trailing_comma_on_call_site" to "true",
+    )
+
+    kotlinGradle {
+        defaults()
+        ktlint().editorConfigOverride(ktlintConfig)
+    }
+
+    kotlin {
+        defaults()
+        ktlint().editorConfigOverride(ktlintConfig)
+    }
+}
diff --git a/buildSrc/src/main/kotlin/cc/tweaked/gradle/CheckLicense.kt b/buildSrc/src/main/kotlin/cc/tweaked/gradle/CheckLicense.kt
new file mode 100644
index 000000000..2217d26be
--- /dev/null
+++ b/buildSrc/src/main/kotlin/cc/tweaked/gradle/CheckLicense.kt
@@ -0,0 +1,73 @@
+package cc.tweaked.gradle
+
+import com.diffplug.spotless.FormatterFunc
+import com.diffplug.spotless.FormatterStep
+import com.diffplug.spotless.generic.LicenseHeaderStep
+import java.io.File
+import java.io.Serializable
+import java.nio.charset.StandardCharsets
+
+/**
+ * Similar to [LicenseHeaderStep], but supports multiple licenses.
+ */
+object LicenseHeader {
+    /**
+     * The current year to use in templates. Intentionally not dynamic to avoid failing the build.
+     */
+    private const val YEAR = 2022
+
+    private val COMMENT = Regex("""^/\*(.*?)\*/\n?""", RegexOption.DOT_MATCHES_ALL)
+
+    fun create(api: File, main: File): FormatterStep = FormatterStep.createLazy(
+        "license",
+        { Licenses(getTemplateText(api), getTemplateText(main)) },
+        { state -> FormatterFunc.NeedsFile { contents, file -> formatFile(state, contents, file) } },
+    )
+
+    private fun getTemplateText(file: File): String =
+        file.readText(StandardCharsets.UTF_8).trim().replace("\${year}", "$YEAR")
+
+    private fun formatFile(licenses: Licenses, contents: String, file: File): String {
+        val license = getLicense(contents)
+        val expectedLicense = getExpectedLicense(licenses, file.parentFile)
+
+        return when {
+            license == null -> setLicense(expectedLicense, contents)
+            license.second != expectedLicense -> setLicense(expectedLicense, contents, license.first)
+            else -> contents
+        }
+    }
+
+    private fun getExpectedLicense(licenses: Licenses, file: File): String {
+        var file: File? = file
+        while (file != null) {
+            if (file.name == "api" && file.parentFile?.name == "computercraft") return licenses.api
+            file = file.parentFile
+        }
+        return licenses.main
+    }
+
+    private fun getLicense(contents: String): Pair<Int, String>? {
+        val match = COMMENT.find(contents) ?: return null
+        val license = match.groups[1]!!.value
+            .trim().lineSequence()
+            .map { it.trimStart(' ', '*') }
+            .joinToString("\n")
+        return Pair(match.range.last + 1, license)
+    }
+
+    private fun setLicense(license: String, contents: String, start: Int = 0): String {
+        val out = StringBuilder()
+        out.append("/*\n")
+        for (line in license.lineSequence()) out.append(" * ").append(line).append("\n")
+        out.append(" */\n")
+        out.append(contents, start, contents.length)
+        return out.toString()
+    }
+
+    private data class Licenses(val api: String, val main: String) : Serializable {
+        companion object {
+            private const val serialVersionUID: Long = 7741106448372435662L
+        }
+    }
+}
diff --git a/gradle/libs.versions.toml b/gradle/libs.versions.toml
index 01d108214..57fe2e8f1 100644
--- a/gradle/libs.versions.toml
+++ b/gradle/libs.versions.toml
@@ -9,6 +9,9 @@ hamcrest = "2.2"
 jqwik = "1.7.0"
 junit = "5.9.1"
 
+# Build tools
+spotless = "6.8.0"
+
 [libraries]
 autoService = { module = "com.google.auto.service:auto-service", version.ref = "autoService" }
 jetbrainsAnnotations = { module = "org.jetbrains:annotations", version.ref = "jetbrainsAnnotations" }
@@ -23,6 +26,9 @@ junit-jupiter-api = { module = "org.junit.jupiter:junit-jupiter-api", version.re
 junit-jupiter-engine = { module = "org.junit.jupiter:junit-jupiter-engine", version.ref = "junit" }
 junit-jupiter-params = { module = "org.junit.jupiter:junit-jupiter-params", version.ref = "junit" }
 
+# Gradle plugins
+spotless = { module = "com.diffplug.spotless:spotless-plugin-gradle", version.ref = "spotless" }
+
 [bundles]
 kotlin = ["kotlin-stdlib", "kotlin-coroutines"]
 
diff --git a/settings.gradle.kts b/settings.gradle.kts
index ede2e9c1e..153e5d000 100644
--- a/settings.gradle.kts
+++ b/settings.gradle.kts
@@ -14,4 +14,4 @@ pluginManagement {
 }
 
 val mc_version: String by settings
-rootProject.name = "cc-tweaked-${mc_version}"
+rootProject.name = "cc-tweaked-$mc_version"
diff --git a/src/test/java/dan200/computercraft/core/apis/AsyncRunner.kt b/src/test/java/dan200/computercraft/core/apis/AsyncRunner.kt
index 450241a2b..1839a8efb 100644
--- a/src/test/java/dan200/computercraft/core/apis/AsyncRunner.kt
+++ b/src/test/java/dan200/computercraft/core/apis/AsyncRunner.kt
@@ -19,7 +19,6 @@ import kotlin.time.Duration
 import kotlin.time.Duration.Companion.seconds
 import kotlin.time.ExperimentalTime
 
-
 abstract class NullApiEnvironment : IAPIEnvironment {
     private val computerEnv = BasicEnvironment()
 
diff --git a/src/test/java/dan200/computercraft/core/apis/http/options/TestHttpApi.kt b/src/test/java/dan200/computercraft/core/apis/http/options/TestHttpApi.kt
index 206924cc0..334af4b5e 100644
--- a/src/test/java/dan200/computercraft/core/apis/http/options/TestHttpApi.kt
+++ b/src/test/java/dan200/computercraft/core/apis/http/options/TestHttpApi.kt
@@ -28,8 +28,8 @@ class TestHttpApi {
             ComputerCraft.httpRules = Collections.unmodifiableList(
                 listOf(
                     AddressRule.parse("\$private", null, Action.DENY.toPartial()),
-                    AddressRule.parse("*", null, Action.ALLOW.toPartial())
-                )
+                    AddressRule.parse("*", null, Action.ALLOW.toPartial()),
+                ),
             )
         }
     }
diff --git a/src/testMod/java/dan200/computercraft/ingame/ComputerTest.kt b/src/testMod/java/dan200/computercraft/ingame/Computer_Test.kt
similarity index 93%
rename from src/testMod/java/dan200/computercraft/ingame/ComputerTest.kt
rename to src/testMod/java/dan200/computercraft/ingame/Computer_Test.kt
index 7935c518a..53c37d078 100644
--- a/src/testMod/java/dan200/computercraft/ingame/ComputerTest.kt
+++ b/src/testMod/java/dan200/computercraft/ingame/Computer_Test.kt
@@ -25,7 +25,8 @@ class Computer_Test {
                 context.assertBlockState(
                     lamp,
                     { !it.getValue(RedstoneLampBlock.LIT) },
-                    { "Lamp should still not be lit" })
+                    { "Lamp should still not be lit" },
+                )
             }
     }
 }
diff --git a/src/testMod/java/dan200/computercraft/ingame/CraftOsTest.kt b/src/testMod/java/dan200/computercraft/ingame/CraftOs_Test.kt
similarity index 100%
rename from src/testMod/java/dan200/computercraft/ingame/CraftOsTest.kt
rename to src/testMod/java/dan200/computercraft/ingame/CraftOs_Test.kt
diff --git a/src/testMod/java/dan200/computercraft/ingame/DiskDriveTest.kt b/src/testMod/java/dan200/computercraft/ingame/Disk_Drive_Test.kt
similarity index 100%
rename from src/testMod/java/dan200/computercraft/ingame/DiskDriveTest.kt
rename to src/testMod/java/dan200/computercraft/ingame/Disk_Drive_Test.kt
diff --git a/src/testMod/java/dan200/computercraft/ingame/ModemTest.kt b/src/testMod/java/dan200/computercraft/ingame/Modem_Test.kt
similarity index 69%
rename from src/testMod/java/dan200/computercraft/ingame/ModemTest.kt
rename to src/testMod/java/dan200/computercraft/ingame/Modem_Test.kt
index 552151a09..2858a0cf5 100644
--- a/src/testMod/java/dan200/computercraft/ingame/ModemTest.kt
+++ b/src/testMod/java/dan200/computercraft/ingame/Modem_Test.kt
@@ -15,10 +15,14 @@ class Modem_Test {
         this
             .thenComputerOk(marker = "initial")
             .thenExecute {
-                helper.setBlock(position, BlockCable.correctConnections(
-                    helper.level, helper.absolutePos(position),
-                    Registry.ModBlocks.CABLE.get().defaultBlockState().setValue(BlockCable.CABLE, true)
-                ))
+                helper.setBlock(
+                    position,
+                    BlockCable.correctConnections(
+                        helper.level,
+                        helper.absolutePos(position),
+                        Registry.ModBlocks.CABLE.get().defaultBlockState().setValue(BlockCable.CABLE, true),
+                    ),
+                )
             }
             .thenComputerOk()
     }
diff --git a/src/testMod/java/dan200/computercraft/ingame/MonitorTest.kt b/src/testMod/java/dan200/computercraft/ingame/Monitor_Test.kt
similarity index 99%
rename from src/testMod/java/dan200/computercraft/ingame/MonitorTest.kt
rename to src/testMod/java/dan200/computercraft/ingame/Monitor_Test.kt
index 4f291b53c..7fc6b5580 100644
--- a/src/testMod/java/dan200/computercraft/ingame/MonitorTest.kt
+++ b/src/testMod/java/dan200/computercraft/ingame/Monitor_Test.kt
@@ -24,7 +24,7 @@ class Monitor_Test {
         val toSet = BlockStateInput(
             Registry.ModBlocks.MONITOR_ADVANCED.get().defaultBlockState(),
             Collections.emptySet(),
-            tag
+            tag,
         )
 
         context.setBlock(pos, Blocks.AIR.defaultBlockState())
diff --git a/src/testMod/java/dan200/computercraft/ingame/PrintoutTest.kt b/src/testMod/java/dan200/computercraft/ingame/Printout_Test.kt
similarity index 94%
rename from src/testMod/java/dan200/computercraft/ingame/PrintoutTest.kt
rename to src/testMod/java/dan200/computercraft/ingame/Printout_Test.kt
index 12b3ac7d7..0de4d44fe 100644
--- a/src/testMod/java/dan200/computercraft/ingame/PrintoutTest.kt
+++ b/src/testMod/java/dan200/computercraft/ingame/Printout_Test.kt
@@ -2,7 +2,7 @@ package dan200.computercraft.ingame
 
 import dan200.computercraft.ingame.api.*
 
-class PrintoutTest {
+class Printout_Test {
     @GameTest(batch = "client:Printout_Test.In_frame_at_night", timeoutTicks = Timeouts.CLIENT_TIMEOUT)
     fun In_frame_at_night(helper: GameTestHelper) = helper.sequence {
         this
diff --git a/src/testMod/java/dan200/computercraft/ingame/TurtleTest.kt b/src/testMod/java/dan200/computercraft/ingame/Turtle_Test.kt
similarity index 97%
rename from src/testMod/java/dan200/computercraft/ingame/TurtleTest.kt
rename to src/testMod/java/dan200/computercraft/ingame/Turtle_Test.kt
index 6245d89ad..d6d6b876f 100644
--- a/src/testMod/java/dan200/computercraft/ingame/TurtleTest.kt
+++ b/src/testMod/java/dan200/computercraft/ingame/Turtle_Test.kt
@@ -86,9 +86,9 @@ class Turtle_Test {
                 DetailRegistries.ITEM_STACK.addProvider(
                     object : BasicItemDetailProvider<ItemPrintout>("printout", ItemPrintout::class.java) {
                         override fun provideDetails(data: MutableMap<in String, Any>, stack: ItemStack, item: ItemPrintout) {
-                            data["type"] = item.type.toString();
+                            data["type"] = item.type.toString()
                         }
-                    }
+                    },
                 )
             }
             .thenComputerOk()
diff --git a/src/testMod/java/dan200/computercraft/ingame/api/GameTestHelper.kt b/src/testMod/java/dan200/computercraft/ingame/api/GameTestHelper.kt
index 9bd69f120..b6f5fe841 100644
--- a/src/testMod/java/dan200/computercraft/ingame/api/GameTestHelper.kt
+++ b/src/testMod/java/dan200/computercraft/ingame/api/GameTestHelper.kt
@@ -79,7 +79,8 @@ typealias GameTestSequence = TestList
 
 typealias GameTestAssertException = RuntimeException
 
-private fun GameTestSequence.addResult(task: () -> Unit, delay: Long? = null): GameTestSequence {
+private fun GameTestSequence.addResult(task: () -> Unit) = addResult(null, task)
+private fun GameTestSequence.addResult(delay: Long?, task: () -> Unit): GameTestSequence {
     val result = UnsafeHacks.newInstance(TestTickResult::class.java) as TestTickResult
     result.assertion = Runnable(task)
     result.expectedDelay = delay
@@ -88,29 +89,29 @@ private fun GameTestSequence.addResult(task: () -> Unit, delay: Long? = null): G
 }
 
 fun GameTestSequence.thenSucceed() {
-    addResult({
+    addResult {
         if (parent.error != null) return@addResult
 
         parent.finish()
         parent.markAsComplete()
-    })
+    }
 }
 
 fun GameTestSequence.thenWaitUntil(task: () -> Unit) = addResult(task)
 
-fun GameTestSequence.thenExecute(task: () -> Unit) = addResult({
+fun GameTestSequence.thenExecute(task: () -> Unit) = addResult {
     try {
         task()
     } catch (e: Exception) {
         parent.fail(e)
     }
-})
+}
 
-fun GameTestSequence.thenIdle(delay: Long) = addResult({
+fun GameTestSequence.thenIdle(delay: Long) = addResult {
     if (parent.tickCount < lastTick + delay) {
         throw GameTestAssertException("Waiting")
     }
-})
+}
 
 /**
  * Proguard strips out all the "on success" code as it's never called anywhere. This is workable most of the time, but
diff --git a/src/testMod/java/dan200/computercraft/ingame/api/TestExtensions.kt b/src/testMod/java/dan200/computercraft/ingame/api/TestExtensions.kt
index 9f34b99c1..dd5a72fce 100644
--- a/src/testMod/java/dan200/computercraft/ingame/api/TestExtensions.kt
+++ b/src/testMod/java/dan200/computercraft/ingame/api/TestExtensions.kt
@@ -99,7 +99,7 @@ fun GameTestSequence.thenScreenshot(name: String? = null): GameTestSequence {
             val screenshotPath = screenshotsPath.resolve("$fullName.png")
             val originalPath = TestMod.sourceDir.resolve("screenshots").resolve("$fullName.png")
 
-            if (!Files.exists(originalPath)) throw GameTestAssertException("$fullName does not exist. Use `/cctest promote' to create it.");
+            if (!Files.exists(originalPath)) throw GameTestAssertException("$fullName does not exist. Use `/cctest promote' to create it.")
 
             val screenshot = ImageIO.read(screenshotPath.toFile())
                 ?: throw GameTestAssertException("Error reading screenshot from $screenshotPath")
@@ -147,14 +147,16 @@ fun GameTestHelper.positionAtArmorStand() {
     player.connection.teleport(stand.x, stand.y, stand.z, stand.yRot, stand.xRot)
 }
 
-
 class ClientTestHelper {
     val minecraft: Minecraft = Minecraft.getInstance()
 
     fun screenshot(name: String, callback: () -> Unit = {}) {
         ScreenShotHelper.grab(
-            minecraft.gameDirectory, name,
-            minecraft.window.width, minecraft.window.height, minecraft.mainRenderTarget
+            minecraft.gameDirectory,
+            name,
+            minecraft.window.width,
+            minecraft.window.height,
+            minecraft.mainRenderTarget,
         ) {
             TestMod.log.info(it.string)
             callback()