diff --git a/.gitignore b/.gitignore
index cb0b8a9b1..d280975d8 100644
--- a/.gitignore
+++ b/.gitignore
@@ -6,3 +6,4 @@ xcuserdata
 *.xccheckout
 .stack-work
 libbridge.dylib
+semantic-diff-profile.*
\ No newline at end of file
diff --git a/prototype/UI/style.css b/prototype/UI/style.css
index 50cbbaccf..98e591dda 100644
--- a/prototype/UI/style.css
+++ b/prototype/UI/style.css
@@ -1,10 +1,20 @@
 table {
-	width: 100%;
+  width: 100%;
+  table-layout: fixed;
 }
 table.diff td {
 	width: 50%;
 	height: 15px;
 }
+
+table.diff td.blob-num {
+  width: 40px;
+}
+
+table.diff td.blob-code {
+  min-width: 100px;
+}
+
 #before, #after {
 	width: 50%;
 }
diff --git a/semantic-diff.cabal b/semantic-diff.cabal
index 2c137b432..9ce2da5d4 100644
--- a/semantic-diff.cabal
+++ b/semantic-diff.cabal
@@ -53,6 +53,25 @@ executable semantic-diff-exe
   extra-libraries:     bridge
   extra-lib-dirs:      .
 
+executable semantic-diff-profile
+  hs-source-dirs:      app
+  main-is:             Main.hs
+  other-modules:       TreeSitter
+  ghc-options:         -O2
+                       -threaded
+                       -fprof-auto
+                       "-with-rtsopts=-N -p -s -h -i0.1"
+  build-depends:       base
+                     , containers
+                     , free
+                     , semantic-diff
+                     , bytestring
+                     , optparse-applicative
+                     , filepath
+  default-language:    Haskell2010
+  extra-libraries:     bridge
+  extra-lib-dirs:      .
+
 test-suite semantic-diff-test
   type:                exitcode-stdio-1.0
   hs-source-dirs:      test
diff --git a/src/Split.hs b/src/Split.hs
index 109373d8b..3f7cbabec 100644
--- a/src/Split.hs
+++ b/src/Split.hs
@@ -10,6 +10,7 @@ import Control.Comonad.Cofree
 import Range
 import Control.Monad.Free
 import Data.ByteString.Lazy.Internal
+import Text.Blaze.Html
 import Text.Blaze.Html5 hiding (map)
 import qualified Text.Blaze.Html5.Attributes as A
 import Text.Blaze.Html.Renderer.Utf8
@@ -62,7 +63,20 @@ split diff before after = return . renderHtml
     . ((head $ link ! A.rel (stringValue "stylesheet") ! A.href (stringValue "style.css")) <>)
     . body
       . (table ! A.class_ (stringValue "diff"))
-        . mconcat $ toMarkup <$> (fst $ diffToRows diff (0, 0) before after)
+        . mconcat $ toMarkup <$> (reverse $ foldl numberRows [] rows)
+   where
+     rows = fst $ diffToRows diff (0, 0) before after
+
+     numberRows :: [(Int, Line, Int, Line)] -> Row -> [(Int, Line, Int, Line)]
+     numberRows [] (Row EmptyLine EmptyLine) = []
+     numberRows [] (Row left@(Line _) EmptyLine) = [(1, left, 0, EmptyLine)]
+     numberRows [] (Row EmptyLine right@(Line _)) = [(0, EmptyLine, 1, right)]
+     numberRows [] (Row left right) = [(1, left, 1, right)]
+     numberRows rows@((leftCount, _, rightCount, _):_) (Row EmptyLine EmptyLine) = (leftCount, EmptyLine, rightCount, EmptyLine):rows
+     numberRows rows@((leftCount, _, rightCount, _):_) (Row left@(Line _) EmptyLine) = (leftCount + 1, left, rightCount, EmptyLine):rows
+     numberRows rows@((leftCount, _, rightCount, _):_) (Row EmptyLine right@(Line _)) = (leftCount, EmptyLine, rightCount + 1, right):rows
+     numberRows rows@((leftCount, _, rightCount, _):_) (Row left right) = (leftCount + 1, left, rightCount + 1, right):rows
+
 
 data Row = Row Line Line
   deriving Eq
@@ -70,12 +84,26 @@ data Row = Row Line Line
 instance Show Row where
   show (Row left right) = "\n" ++ show left ++ " | " ++ show right
 
-instance ToMarkup Row where
-  toMarkup (Row left right) = (tr $ toMarkup left <> toMarkup right) <> string "\n"
+instance ToMarkup (Int, Line, Int, Line) where
+  toMarkup (_, EmptyLine, _, EmptyLine) = tr $ numberTd "" <> td (string "") <> numberTd "" <> toMarkup (string "") <> string "\n"
+  toMarkup (_, EmptyLine, num, right) = tr $ numberTd "" <> td (string "") <>
+                                               numberTd (show num) <> toMarkup right <> string "\n"
+  toMarkup (num, left, _, EmptyLine) = tr $ numberTd (show num)  <> toMarkup left <>
+                                              numberTd "" <> td (string "") <> string "\n"
+  toMarkup (leftNum, left, rightNum, right) = tr $ numberTd (show leftNum) <> toMarkup left <>
+                                          numberTd (show rightNum) <> toMarkup right <> string "\n"
+
+numberTd :: String -> Html
+numberTd s = td (string s) ! A.class_ (stringValue "blob-num")
+
+codeTd :: Html -> Html
+codeTd el = td el ! A.class_ (stringValue "blob-code")
+--instance ToMarkup Row where
+--  toMarkup (Row left right) = (tr $ toMarkup left <> toMarkup right) <> string "\n"
 
 instance ToMarkup Line where
-  toMarkup EmptyLine = td (string "")
-  toMarkup (Line html) = td . mconcat $ toMarkup <$> html
+  toMarkup EmptyLine = codeTd (string "")
+  toMarkup (Line html) = codeTd . mconcat $ toMarkup <$> html
 
 data Line =
   Line [HTML]