diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 31f3be2..5c0b800 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -37,6 +37,8 @@ jobs:
           - 2.13.3
           - 2.13.4
           - 2.13.5
+          - 3.0.0-M3
+          - 3.0.0-RC1
         java: [graalvm-ce-java11@20.3.0]
     runs-on: ${{ matrix.os }}
     steps:
@@ -84,7 +86,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest]
-        scala: [2.12.10]
+        scala: [3.0.0-RC1]
         java: [graalvm-ce-java11@20.3.0]
     runs-on: ${{ matrix.os }}
     steps:
@@ -200,6 +202,26 @@ jobs:
           tar xf targets.tar
           rm targets.tar
 
+      - name: Download target directories (3.0.0-M3)
+        uses: actions/download-artifact@v2
+        with:
+          name: target-${{ matrix.os }}-3.0.0-M3-${{ matrix.java }}
+
+      - name: Inflate target directories (3.0.0-M3)
+        run: |
+          tar xf targets.tar
+          rm targets.tar
+
+      - name: Download target directories (3.0.0-RC1)
+        uses: actions/download-artifact@v2
+        with:
+          name: target-${{ matrix.os }}-3.0.0-RC1-${{ matrix.java }}
+
+      - name: Inflate target directories (3.0.0-RC1)
+        run: |
+          tar xf targets.tar
+          rm targets.tar
+
       - uses: olafurpg/setup-gpg@v3
 
       - run: sbt ++${{ matrix.scala }} ci-release
\ No newline at end of file
diff --git a/build.sbt b/build.sbt
index 8397451..e246703 100644
--- a/build.sbt
+++ b/build.sbt
@@ -18,7 +18,7 @@ inThisBuild(
 
 val GraalVM11 = "graalvm-ce-java11@20.3.0"
 
-ThisBuild / scalaVersion := "2.12.10"
+ThisBuild / scalaVersion := "3.0.0-RC1"
 ThisBuild / crossScalaVersions := Seq(
   "2.12.10",
   "2.12.11",
@@ -29,7 +29,10 @@ ThisBuild / crossScalaVersions := Seq(
   "2.13.2",
   "2.13.3",
   "2.13.4",
-  "2.13.5"
+  "2.13.5",
+  //
+  "3.0.0-M3",
+  "3.0.0-RC1"
 )
 
 ThisBuild / githubWorkflowJavaVersions := Seq(GraalVM11)
@@ -57,13 +60,22 @@ val commonSettings = Seq(
   scalacOptions -= "-Xfatal-warnings"
 )
 
+def scalatestVersion(scalaVersion: String) = scalaVersion match {
+  case "3.0.0-M3" => "3.2.3"
+  case _          => "3.2.5"
+}
+
 val plugin = project.settings(
   name := "better-tostring",
   commonSettings,
   crossTarget := target.value / s"scala-${scalaVersion.value}", // workaround for https://github.com/sbt/sbt/issues/5097
   crossVersion := CrossVersion.full,
   libraryDependencies ++= Seq(
-    scalaOrganization.value % "scala-compiler" % scalaVersion.value
+    scalaOrganization.value % (
+      if (isDotty.value)
+        s"scala3-compiler_${scalaVersion.value}"
+      else "scala-compiler"
+    ) % scalaVersion.value
   )
 )
 
@@ -79,7 +91,7 @@ val tests = project.settings(
     ) //borrowed from bm4
   },
   libraryDependencies ++= Seq(
-    "org.scalatest" %% "scalatest" % "3.2.5" % Test
+    "org.scalatest" %% "scalatest" % scalatestVersion(scalaVersion.value) % Test
   )
 )
 
diff --git a/plugin/src/main/resources/plugin.properties b/plugin/src/main/resources/plugin.properties
new file mode 100644
index 0000000..cc0ddac
--- /dev/null
+++ b/plugin/src/main/resources/plugin.properties
@@ -0,0 +1 @@
+pluginClass=com.kubukoz.BetterToStringPlugin
diff --git a/plugin/src/main/scala-2/BetterToStringPlugin.scala b/plugin/src/main/scala-2/BetterToStringPlugin.scala
new file mode 100644
index 0000000..954b04c
--- /dev/null
+++ b/plugin/src/main/scala-2/BetterToStringPlugin.scala
@@ -0,0 +1,50 @@
+package com.kubukoz
+
+import scala.tools.nsc.Global
+import scala.tools.nsc.Phase
+import scala.tools.nsc.plugins.Plugin
+import scala.tools.nsc.plugins.PluginComponent
+import scala.tools.nsc.transform.TypingTransformers
+
+final class BetterToStringPlugin(override val global: Global) extends Plugin {
+  override val name: String = "better-tostring"
+  override val description: String =
+    "scala compiler plugin for better default toString implementations"
+  override val components: List[PluginComponent] = List(
+    new BetterToStringPluginComponent(global)
+  )
+}
+
+final class BetterToStringPluginComponent(val global: Global)
+    extends PluginComponent
+    with TypingTransformers {
+  import global._
+  override val phaseName: String = "better-tostring-phase"
+  override val runsAfter: List[String] = List("parser")
+
+  private val impl: BetterToStringImpl[Scala2CompilerApi[global.type]] =
+    BetterToStringImpl.instance(Scala2CompilerApi.instance(global))
+
+  private def modifyClasses(tree: Tree): Tree =
+    tree match {
+      case p: PackageDef => p.copy(stats = p.stats.map(modifyClasses))
+      case m: ModuleDef =>
+        m.copy(impl = m.impl.copy(body = m.impl.body.map(modifyClasses)))
+      case clazz: ClassDef =>
+        impl.transformClass(
+          clazz,
+          // If it was nested, we wouldn't be in this branch.
+          // Scala 2.x compiler API limitation (classes can't tell what the owner is).
+          // This should be more optimal as we don't traverse every template, but it hasn't been benchmarked.
+          isNested = false
+        )
+      case other => other
+    }
+
+  override def newPhase(prev: Phase): Phase = new StdPhase(prev) {
+    override def apply(unit: CompilationUnit): Unit =
+      new Transformer {
+        override def transform(tree: Tree): Tree = modifyClasses(tree)
+      }.transformUnit(unit)
+  }
+}
diff --git a/plugin/src/main/scala-2/Scala2CompilerApi.scala b/plugin/src/main/scala-2/Scala2CompilerApi.scala
new file mode 100644
index 0000000..e1bce89
--- /dev/null
+++ b/plugin/src/main/scala-2/Scala2CompilerApi.scala
@@ -0,0 +1,50 @@
+package com.kubukoz
+
+import scala.reflect.internal.Flags
+import scala.tools.nsc.Global
+
+trait Scala2CompilerApi[G <: Global] extends CompilerApi {
+  val theGlobal: G
+  import theGlobal._
+  type Tree = theGlobal.Tree
+  type Clazz = ClassDef
+  type Param = ValDef
+  type ParamName = TermName
+  type Method = DefDef
+}
+
+object Scala2CompilerApi {
+  def instance(global: Global): Scala2CompilerApi[global.type] =
+    new Scala2CompilerApi[global.type] {
+      val theGlobal: global.type = global
+      import global._
+
+      def params(clazz: Clazz): List[Param] = clazz.impl.body.collect {
+        case v: ValDef if v.mods.hasFlag(Flags.CASEACCESSOR) => v
+      }
+
+      def className(clazz: Clazz): String = clazz.name.toString
+      def literalConstant(value: String): Tree = Literal(Constant(value))
+      def paramName(param: Param): ParamName = param.name
+      def selectInThis(clazz: Clazz, name: ParamName): Tree = q"this.$name"
+      def concat(l: Tree, r: Tree): Tree = q"$l + $r"
+
+      def createToString(clazz: Clazz, body: Tree): Method = DefDef(
+        Modifiers(Flags.OVERRIDE),
+        TermName("toString"),
+        Nil,
+        List(List()),
+        Ident(TypeName("String")),
+        body
+      )
+
+      def addMethod(clazz: Clazz, method: Method): Clazz =
+        clazz.copy(impl = clazz.impl.copy(body = clazz.impl.body :+ method))
+
+      def methodNames(clazz: Clazz): List[String] = clazz.impl.body.collect {
+        case d: DefDef => d.name.toString
+      }
+
+      def isCaseClass(clazz: Clazz): Boolean = clazz.mods.hasFlag(Flags.CASE)
+    }
+}
diff --git a/plugin/src/main/scala-3/BetterToStringPlugin.scala b/plugin/src/main/scala-3/BetterToStringPlugin.scala
new file mode 100644
index 0000000..6a36fbe
--- /dev/null
+++ b/plugin/src/main/scala-3/BetterToStringPlugin.scala
@@ -0,0 +1,28 @@
+package com.kubukoz
+
+import dotty.tools.dotc.ast.tpd
+import dotty.tools.dotc.core.Contexts.Context
+import dotty.tools.dotc.core.Flags.Module
+import dotty.tools.dotc.plugins.{PluginPhase, StandardPlugin}
+import dotty.tools.dotc.typer.FrontEnd
+import tpd._
+
+final class BetterToStringPlugin extends StandardPlugin:
+  override val name: String = "better-tostring"
+  override val description: String = "scala compiler plugin for better default toString implementations"
+  override def init(options: List[String]): List[PluginPhase] = List(new BetterToStringPluginPhase)
+
+final class BetterToStringPluginPhase extends PluginPhase:
+
+  override val phaseName: String = "better-tostring-phase"
+  override val runsAfter: Set[String] = Set(FrontEnd.name)
+
+  override def transformTemplate(t: Template)(using ctx: Context): Tree =
+    val clazz = ctx.owner.asClass
+
+    val isNested = !(ctx.owner.owner.isPackageObject || ctx.owner.owner.is(Module))
+
+    BetterToStringImpl
+      .instance(Scala3CompilerApi.instance)
+      .transformClass(Scala3CompilerApi.ClassContext(t, clazz), isNested)
+      .t
diff --git a/plugin/src/main/scala-3/Scala3CompilerApi.scala b/plugin/src/main/scala-3/Scala3CompilerApi.scala
new file mode 100644
index 0000000..0f93c29
--- /dev/null
+++ b/plugin/src/main/scala-3/Scala3CompilerApi.scala
@@ -0,0 +1,64 @@
+package com.kubukoz
+
+import dotty.tools.dotc.ast.tpd
+import dotty.tools.dotc.core.Contexts.Context
+import dotty.tools.dotc.core.Symbols
+import dotty.tools.dotc.core.Flags.CaseAccessor
+import dotty.tools.dotc.core.Flags.CaseClass
+import dotty.tools.dotc.core.Flags.Override
+import dotty.tools.dotc.core.Types
+import dotty.tools.dotc.core.Names
+import dotty.tools.dotc.core.Constants.Constant
+import dotty.tools.dotc.core.Symbols.ClassSymbol
+import dotty.tools.dotc.core.Decorators._
+import dotty.tools.dotc.ast.Trees
+import tpd._
+
+trait Scala3CompilerApi extends CompilerApi:
+  type Tree = Trees.Tree[Types.Type]
+  type Clazz = Scala3CompilerApi.ClassContext
+  type Param = ValDef
+  type ParamName = Names.TermName
+  type Method = DefDef
+
+object Scala3CompilerApi:
+  final case class ClassContext(t: Template, clazz: ClassSymbol):
+    def mapTemplate(f: Template => Template): ClassContext = copy(t = f(t))
+
+  def instance(using Context): Scala3CompilerApi = new Scala3CompilerApi:
+    def params(clazz: Clazz): List[Param] =
+      clazz.t.body.collect {
+        case v: ValDef if v.mods.is(CaseAccessor) => v
+      }
+
+    def className(clazz: Clazz): String = clazz.clazz.name.toString
+    def literalConstant(value: String): Tree = Literal(Constant(value))
+    def paramName(param: Param): ParamName = param.name
+    def selectInThis(clazz: Clazz, name: ParamName): Tree = This(clazz.clazz).select(name)
+    def concat(l: Tree, r: Tree): Tree = l.select("+".toTermName).appliedTo(r)
+
+    def createToString(owner: Clazz, body: Tree): Method = {
+      val clazz = owner.clazz
+      // this was adapted from dotty.tools.dotc.transform.SyntheticMembers (line 115)
+      val sym = Symbols.defn.Any_toString
+
+      val toStringSymbol = sym.copy(
+        owner = clazz,
+        flags = sym.flags | Override,
+        info = clazz.thisType.memberInfo(sym),
+        coord = clazz.coord
+      ).entered.asTerm
+
+      DefDef(toStringSymbol, body)
+    }
+
+    def addMethod(clazz: Clazz, method: Method): Clazz =
+      clazz.mapTemplate(
+        t => cpy.Template(t)(body = t.body :+ method)
+      )
+
+    def methodNames(clazz: Clazz): List[String] = clazz.t.body.collect {
+      case d: DefDef => d.name.toString
+    }
+
+    def isCaseClass(clazz: Clazz): Boolean = clazz.clazz.flags.is(CaseClass)
diff --git a/plugin/src/main/scala/BetterToStringImpl.scala b/plugin/src/main/scala/BetterToStringImpl.scala
new file mode 100644
index 0000000..41dc2e3
--- /dev/null
+++ b/plugin/src/main/scala/BetterToStringImpl.scala
@@ -0,0 +1,85 @@
+package com.kubukoz
+
+// Source-compatible core between 2.x and 3.x implementations
+
+trait CompilerApi {
+  type Tree
+  type Clazz
+  type Param
+  type ParamName
+  type Method
+
+  def className(clazz: Clazz): String
+  def params(clazz: Clazz): List[Param]
+  def literalConstant(value: String): Tree
+
+  def paramName(param: Param): ParamName
+  def selectInThis(clazz: Clazz, name: ParamName): Tree
+  def concat(l: Tree, r: Tree): Tree
+
+  def createToString(clazz: Clazz, body: Tree): Method
+  def addMethod(clazz: Clazz, method: Method): Clazz
+  def methodNames(clazz: Clazz): List[String]
+  def isCaseClass(clazz: Clazz): Boolean
+}
+
+trait BetterToStringImpl[+C <: CompilerApi] {
+  val compilerApi: C
+
+  def transformClass(
+      clazz: compilerApi.Clazz,
+      isNested: Boolean
+  ): compilerApi.Clazz
+}
+
+object BetterToStringImpl {
+  def instance(
+      api: CompilerApi
+  ): BetterToStringImpl[api.type] =
+    new BetterToStringImpl[api.type] {
+      val compilerApi: api.type = api
+
+      import api._
+
+      def transformClass(
+          clazz: Clazz,
+          isNested: Boolean
+      ): Clazz = {
+        val hasToString: Boolean = methodNames(clazz).contains("toString")
+
+        val shouldModify =
+          isCaseClass(clazz) && !isNested && !hasToString
+
+        if (shouldModify) overrideToString(clazz)
+        else clazz
+      }
+
+      private def overrideToString(clazz: Clazz): Clazz =
+        addMethod(clazz, createToString(clazz, toStringImpl(clazz)))
+
+      private def toStringImpl(clazz: Clazz): Tree = {
+        val className = api.className(clazz)
+
+        val paramListParts: List[Tree] = params(clazz).zipWithIndex.flatMap {
+          case (v, index) =>
+            val commaPrefix = if (index > 0) ", " else ""
+
+            val name = paramName(v)
+
+            List(
+              literalConstant(commaPrefix ++ name.toString ++ " = "),
+              selectInThis(clazz, name)
+            )
+        }
+
+        val parts =
+          List(
+            List(literalConstant(className ++ "(")),
+            paramListParts,
+            List(literalConstant(")"))
+          ).flatten
+
+        parts.reduceLeft(concat(_, _))
+      }
+    }
+}
diff --git a/plugin/src/main/scala/BetterToStringPlugin.scala b/plugin/src/main/scala/BetterToStringPlugin.scala
deleted file mode 100644
index 63bb4aa..0000000
--- a/plugin/src/main/scala/BetterToStringPlugin.scala
+++ /dev/null
@@ -1,92 +0,0 @@
-package com.kubukoz
-
-import scala.tools.nsc.plugins.{Plugin, PluginComponent}
-import scala.tools.nsc.{Global, Phase}
-import scala.tools.nsc.transform.TypingTransformers
-import scala.reflect.internal.Flags
-
-class BetterToStringPlugin(override val global: Global) extends Plugin {
-  override val name: String = "better-tostring"
-  override val description: String = "scala compiler plugin for better default toString implementations"
-  override val components: List[PluginComponent] = List(new BetterToStringPluginComponent(global))
-}
-
-class BetterToStringPluginComponent(val global: Global) extends PluginComponent with TypingTransformers {
-  import global._
-  override val phaseName: String = "better-tostring-phase"
-  override val runsAfter: List[String] = List("parser")
-
-  private def addToString(clazz: ClassDef): ClassDef = {
-    val params = clazz.impl.body.collect {
-      case v: ValDef if v.mods.hasFlag(Flags.CASEACCESSOR) => v
-    }
-
-    val toStringImpl: Tree = {
-      val className = clazz.name.toString()
-
-      val paramListParts: List[Tree] = params.zipWithIndex.flatMap {
-        case (v, index) =>
-          val commaPrefix = if (index > 0) ", " else ""
-
-          List(
-            Literal(Constant(commaPrefix ++ v.name.toString ++ " = ")),
-            q"this.${v.name}"
-          )
-      }
-
-      val parts =
-        List(
-          List(Literal(Constant(className ++ "("))),
-          paramListParts,
-          List(Literal(Constant(")")))
-        ).flatten
-
-      parts.reduceLeft((a, b) => q"$a + $b")
-    }
-
-    val methodBody = DefDef(
-      Modifiers(Flags.OVERRIDE),
-      TermName("toString"),
-      Nil,
-      List(List()),
-      Ident(TypeName("String")),
-      toStringImpl
-    )
-
-    clazz.copy(impl = clazz.impl.copy(body = clazz.impl.body :+ methodBody))
-  }
-
-  private def transformClass(clazz: ClassDef): ClassDef = {
-    val hasCustomToString: Boolean = clazz.impl.body.exists {
-
-      case fun: DefDef =>
-        //so meta
-        fun.name.toString == "toString"
-      case _ => false
-    }
-
-    val shouldModify = !hasCustomToString
-
-    if (shouldModify) addToString(clazz)
-    else clazz
-  }
-
-  private def modifyClasses(f: ClassDef => ClassDef)(tree: Tree): Tree = tree match {
-    case p: PackageDef => p.copy(stats = p.stats.map(modifyClasses(f)))
-    case m: ModuleDef  => m.copy(impl = m.impl.copy(body = m.impl.body.map(modifyClasses(f))))
-    //Only case classes
-    case clazz: ClassDef if clazz.mods.hasFlag(Flags.CASE) => f(clazz)
-    case other                                             => other
-  }
-
-  override def newPhase(prev: Phase): Phase = new StdPhase(prev) {
-
-    override def apply(unit: CompilationUnit): Unit = {
-      val trans = new Transformer {
-        override def transform(tree: Tree): Tree = modifyClasses(transformClass)(tree)
-      }
-
-      trans.transformUnit(unit)
-    }
-  }
-}
diff --git a/project/plugins.sbt b/project/plugins.sbt
index 7c59508..82e1c27 100644
--- a/project/plugins.sbt
+++ b/project/plugins.sbt
@@ -1,3 +1,4 @@
 addSbtPlugin("com.geirsson" % "sbt-ci-release" % "1.5.5")
 addSbtPlugin("io.github.davidgregory084" % "sbt-tpolecat" % "0.1.16")
 addSbtPlugin("com.codecommit" % "sbt-github-actions" % "0.10.1")
+addSbtPlugin("ch.epfl.lamp" % "sbt-dotty" % "0.5.3")