diff --git a/library/TextBuilderDev.hs b/library/TextBuilderDev.hs
--- a/library/TextBuilderDev.hs
+++ b/library/TextBuilderDev.hs
@@ -83,6 +83,8 @@
 import qualified Data.Text.Encoding.Error as E
 import qualified Data.Text.IO as Text
 import qualified Data.Text.Internal as C
+import qualified Data.Text.Lazy as TextLazy
+import qualified Data.Text.Lazy.Builder as TextLazyBuilder
 import qualified DeferredFolds.Unfoldr as Unfoldr
 import TextBuilderDev.Prelude hiding (intercalate, length, null)
 #if MIN_VERSION_text(2,0,0)
@@ -90,8 +92,6 @@
 #else
 import qualified TextBuilderDev.UTF16 as D
 #endif
-import qualified Data.Text.Lazy as TextLazy
-import qualified Data.Text.Lazy.Builder as TextLazyBuilder
 
 -- * --
 
@@ -180,6 +180,33 @@
 
 instance Eq TextBuilder where
   (==) = on (==) buildText
+
+instance IsomorphicTo TextBuilder TextBuilder where
+  to = id
+
+instance IsomorphicTo TextBuilder String where
+  to = TextBuilderDev.string
+
+instance IsomorphicTo TextBuilder Text where
+  to = TextBuilderDev.text
+
+instance IsomorphicTo TextBuilder TextLazy.Text where
+  to = TextBuilderDev.lazyText
+
+instance IsomorphicTo TextBuilder TextLazyBuilder.Builder where
+  to = to . to @TextLazy.Text
+
+instance IsomorphicTo String TextBuilder where
+  to = to . to @Text
+
+instance IsomorphicTo Text TextBuilder where
+  to = TextBuilderDev.buildText
+
+instance IsomorphicTo TextLazy.Text TextBuilder where
+  to = to . to @Text
+
+instance IsomorphicTo TextLazyBuilder.Builder TextBuilder where
+  to = to . to @Text
 
 -- * Accessors
 
diff --git a/library/TextBuilderDev/Prelude.hs b/library/TextBuilderDev/Prelude.hs
--- a/library/TextBuilderDev/Prelude.hs
+++ b/library/TextBuilderDev/Prelude.hs
@@ -61,6 +61,7 @@
 import GHC.Exts as Exports (groupWith, inline, lazy, sortWith)
 import GHC.Generics as Exports (Generic)
 import GHC.IO.Exception as Exports
+import IsomorphismClass as Exports
 import Numeric as Exports
 import System.Environment as Exports
 import System.Exit as Exports
diff --git a/text-builder-dev.cabal b/text-builder-dev.cabal
--- a/text-builder-dev.cabal
+++ b/text-builder-dev.cabal
@@ -1,7 +1,7 @@
 cabal-version: 3.0
 
 name: text-builder-dev
-version: 0.3.2
+version: 0.3.3
 category: Text
 synopsis: Edge of developments for "text-builder"
 description:
@@ -40,6 +40,7 @@
     base >=4.11 && <5,
     bytestring >=0.10 && <0.12,
     deferred-folds >=0.9.10.1 && <0.10,
+    isomorphism-class >=0.1.0.1 && <0.2,
     split >=0.2.3.4 && <0.3,
     text >=1.0 && <3,
     transformers >=0.5 && <0.7,