diff --git a/src/Slab/Build.hs b/src/Slab/Build.hs
index b6fdad3..febb615 100644
--- a/src/Slab/Build.hs
+++ b/src/Slab/Build.hs
@@ -43,7 +43,7 @@ buildFile :: FilePath -> Command.RenderMode -> Command.RunMode -> FilePath -> Fi
 buildFile srcDir mode passthrough distDir path = do
   let path' = distDir </> replaceExtension (makeRelative srcDir path) ".html"
       dir' = takeDirectory path'
-      ctx = Execute.Context path passthrough
+      ctx = Execute.Context (Just path) passthrough
   putStrLn $ "Building " <> path' <> "..."
   createDirectoryIfMissing True dir'
 
@@ -72,7 +72,7 @@ buildDirInMemory srcDir mode passthrough store = do
 buildFileInMemory :: FilePath -> Command.RenderMode -> Command.RunMode -> StmStore -> FilePath -> IO ()
 buildFileInMemory srcDir mode passthrough store path = do
   let path' = replaceExtension (makeRelative srcDir path) ".html"
-      ctx = Execute.Context path passthrough
+      ctx = Execute.Context (Just path) passthrough
   putStrLn $ "Building " <> path' <> "..."
 
   mnodes <- Execute.executeFile ctx
diff --git a/src/Slab/Command.hs b/src/Slab/Command.hs
index 9739b8b..bf93844 100644
--- a/src/Slab/Command.hs
+++ b/src/Slab/Command.hs
@@ -31,12 +31,13 @@ data Command
   | Watch FilePath RenderMode RunMode FilePath
   | Serve FilePath FilePath
   | ReportPages FilePath
-  | ReportHeadings FilePath
+  | ReportHeadings (Maybe FilePath)
   | -- | Return the content of element matching the provided ID.
-    ReportElement Text FilePath
+    ReportElement Text (Maybe FilePath)
   | -- | Generate code. Only Haskell for now.
-    Generate FilePath
-  | CommandWithPath FilePath ParseMode CommandWithPath
+    Generate (Maybe FilePath)
+  | -- | When the filepath is Nothing, use stdin.
+    CommandWithPath (Maybe FilePath) ParseMode CommandWithPath
 
 -- | Commands operating on a path.
 data CommandWithPath
@@ -223,8 +224,8 @@ parserReportPages = do
 
 parserReportHeadings :: A.Parser Command
 parserReportHeadings = do
-  path <- parserTemplatePath
-  pure $ ReportHeadings path
+  mpath <- parserTemplatePath
+  pure $ ReportHeadings mpath
 
 parserReportElement :: A.Parser Command
 parserReportElement = do
@@ -232,8 +233,8 @@ parserReportElement = do
     A.argument
       A.str
       (A.metavar "ID" <> A.help "Element ID to match.")
-  path <- parserTemplatePath
-  pure $ ReportElement id_ path
+  mpath <- parserTemplatePath
+  pure $ ReportElement id_ mpath
 
 parserWatch :: A.Parser Command
 parserWatch = do
@@ -296,8 +297,8 @@ parserParse = do
 
 parserGenerate :: A.Parser Command
 parserGenerate = do
-  path <- parserTemplatePath
-  pure $ Generate path
+  mpath <- parserTemplatePath
+  pure $ Generate mpath
 
 parserClasses :: A.Parser Command
 parserClasses = do
@@ -315,14 +316,19 @@ parserFragments = do
   pure $ uncurry CommandWithPath pathAndmode $ Fragments mname
 
 --------------------------------------------------------------------------------
-parserWithPath :: A.Parser (FilePath, ParseMode)
+parserWithPath :: A.Parser (Maybe FilePath, ParseMode)
 parserWithPath = (,) <$> parserTemplatePath <*> parserShallowFlag
 
-parserTemplatePath :: A.Parser FilePath
-parserTemplatePath =
-  A.argument
+parserTemplatePath :: A.Parser (Maybe FilePath)
+parserTemplatePath = do
+  path <- A.argument
     A.str
     (A.metavar "FILE" <> A.action "file" <> A.help "Slab template to parse.")
+  pure (
+    if path == "-"
+    then Nothing
+    else Just path
+    )
 
 parserShallowFlag :: A.Parser ParseMode
 parserShallowFlag =
diff --git a/src/Slab/Evaluate.hs b/src/Slab/Evaluate.hs
index 05afec9..91e5cdd 100644
--- a/src/Slab/Evaluate.hs
+++ b/src/Slab/Evaluate.hs
@@ -35,12 +35,12 @@ import Slab.Syntax
 --------------------------------------------------------------------------------
 
 -- | Similar to `preprocessFile` but evaluate the template.
-evaluateFile :: FilePath -> IO (Either Error.Error [Block])
+evaluateFile :: Maybe FilePath -> IO (Either Error.Error [Block])
 evaluateFile = runExceptT . evaluateFileE
 
-evaluateFileE :: FilePath -> ExceptT Error.Error IO [Block]
-evaluateFileE path =
-  PreProcess.preprocessFileE path >>= evaluate defaultEnv [T.pack path]
+evaluateFileE :: Maybe FilePath -> ExceptT Error.Error IO [Block]
+evaluateFileE mpath =
+  PreProcess.preprocessFileE mpath >>= evaluate defaultEnv [maybe "-" T.pack mpath]
 
 --------------------------------------------------------------------------------
 defaultEnv :: Env
diff --git a/src/Slab/Execute.hs b/src/Slab/Execute.hs
index 92ce653..a99409b 100644
--- a/src/Slab/Execute.hs
+++ b/src/Slab/Execute.hs
@@ -30,7 +30,7 @@ import System.Process (readCreateProcessWithExitCode, shell)
 
 --------------------------------------------------------------------------------
 data Context = Context
-  { ctxPath :: FilePath
+  { ctxPath :: Maybe FilePath
   , ctxRunMode :: Command.RunMode
   }
 
diff --git a/src/Slab/Generate/Haskell.hs b/src/Slab/Generate/Haskell.hs
index 6d3b738..4f1edd7 100644
--- a/src/Slab/Generate/Haskell.hs
+++ b/src/Slab/Generate/Haskell.hs
@@ -20,9 +20,9 @@ import Slab.PreProcess qualified as PreProcess
 import Slab.Syntax qualified as Syntax
 
 --------------------------------------------------------------------------------
-renderHs :: FilePath -> IO ()
-renderHs path = do
-  blocks <- PreProcess.preprocessFile path >>= Error.unwrap
+renderHs :: Maybe FilePath -> IO ()
+renderHs mpath = do
+  blocks <- PreProcess.preprocessFile mpath >>= Error.unwrap
   T.putStrLn $ renderModule blocks
 
 renderModule :: [Syntax.Block] -> Text
diff --git a/src/Slab/Parse.hs b/src/Slab/Parse.hs
index fd83026..5feb4f4 100644
--- a/src/Slab/Parse.hs
+++ b/src/Slab/Parse.hs
@@ -44,13 +44,15 @@ import Text.Megaparsec.Char
 import Text.Megaparsec.Char.Lexer qualified as L
 
 --------------------------------------------------------------------------------
-parseFile :: FilePath -> IO (Either Error.Error [Block])
+parseFile :: Maybe FilePath -> IO (Either Error.Error [Block])
 parseFile = runExceptT . parseFileE
 
-parseFileE :: FilePath -> ExceptT Error.Error IO [Block]
-parseFileE path = do
-  content <- liftIO $ T.readFile path
-  withExceptT Error.ParseError . except $ parse path content
+parseFileE :: Maybe FilePath -> ExceptT Error.Error IO [Block]
+parseFileE mpath = do
+  content <- liftIO $ case mpath of
+    Just path -> T.readFile path
+    Nothing -> T.getContents
+  withExceptT Error.ParseError . except $ parse (maybe "-" id mpath) content
 
 --------------------------------------------------------------------------------
 
diff --git a/src/Slab/PreProcess.hs b/src/Slab/PreProcess.hs
index 69b6d25..d732652 100644
--- a/src/Slab/PreProcess.hs
+++ b/src/Slab/PreProcess.hs
@@ -37,15 +37,15 @@ data Context = Context
 --------------------------------------------------------------------------------
 
 -- | Similar to `parseFile` but pre-process the include statements.
-preprocessFile :: FilePath -> IO (Either Error.Error [Block])
+preprocessFile :: Maybe FilePath -> IO (Either Error.Error [Block])
 preprocessFile = runExceptT . preprocessFileE
 
-preprocessFileE :: FilePath -> ExceptT Error.Error IO [Block]
-preprocessFileE path = do
-  nodes <- Parse.parseFileE path
+preprocessFileE :: Maybe FilePath -> ExceptT Error.Error IO [Block]
+preprocessFileE mpath = do
+  nodes <- Parse.parseFileE mpath
   let ctx =
         Context
-          { ctxStartPath = path
+          { ctxStartPath = maybe "." id mpath
           }
   preprocess ctx nodes
 
@@ -75,7 +75,7 @@ preproc ctx@Context {..} = \case
             pure $ BlockInclude mname path (Just [node])
         | exists -> do
             -- Parse and process the .slab file.
-            nodes' <- preprocessFileE includedPath
+            nodes' <- preprocessFileE (Just includedPath)
             pure $ BlockInclude mname path (Just nodes')
         | otherwise ->
             throwE $ Error.PreProcessError $ "File " <> T.pack includedPath <> " doesn't exist"
@@ -103,7 +103,7 @@ preproc ctx@Context {..} = \case
             throwE $ Error.PreProcessError $ "Extends requires a .slab file"
         | exists -> do
             -- Parse and process the .slab file.
-            body <- preprocessFileE includedPath
+            body <- preprocessFileE (Just includedPath)
             args' <- mapM (preproc ctx) args
             pure $ BlockImport path (Just body) args'
         | otherwise ->
diff --git a/src/Slab/Report.hs b/src/Slab/Report.hs
index 1652ed6..8d07fc6 100644
--- a/src/Slab/Report.hs
+++ b/src/Slab/Report.hs
@@ -42,17 +42,17 @@ isPage Module {moduleNodes = (x : _)} = Syntax.isDoctype x
 isPage _ = False
 
 --------------------------------------------------------------------------------
-reportHeadings :: FilePath -> IO ()
-reportHeadings path = do
-  modl <- buildFile False path
+reportHeadings :: Maybe FilePath -> IO ()
+reportHeadings mpath = do
+  modl <- buildFile False mpath
   let headings = extractHeadings . Evaluate.simplify $ moduleNodes modl
       f (Heading level _ t) = show level <> " " <> T.unpack t
   putStrLn . drawForest . map (fmap f) $ buildTrees headings
 
 --------------------------------------------------------------------------------
-reportElement :: Text -> FilePath -> IO ()
-reportElement i path = do
-  modl <- buildFile True path
+reportElement :: Text -> Maybe FilePath -> IO ()
+reportElement i mpath = do
+  modl <- buildFile True mpath
   let me = extractElement i . Evaluate.simplify $ moduleNodes modl
   case me of
     Just e -> pPrintNoColor e >> exitSuccess
@@ -65,15 +65,15 @@ reportElement i path = do
 buildDir :: FilePath -> IO [Module]
 buildDir srcDir = do
   templates <- Build.listTemplates srcDir
-  mapM (buildFile False) templates
+  mapM (buildFile False . Just) templates
 
-buildFile :: Bool -> FilePath -> IO Module
-buildFile quiet path = do
-  when (not quiet) $ putStrLn $ "Reading " <> path <> "..."
-  nodes <- Evaluate.evaluateFile path >>= Error.unwrap
+buildFile :: Bool -> Maybe FilePath -> IO Module
+buildFile quiet mpath = do
+  when (not quiet) $ putStrLn $ "Reading " <> maybe "stdin" id mpath <> "..."
+  nodes <- Evaluate.evaluateFile mpath >>= Error.unwrap
   pure
     Module
-      { modulePath = path
+      { modulePath = maybe "." id mpath
       , moduleNodes = nodes
       }
 
diff --git a/src/Slab/Run.hs b/src/Slab/Run.hs
index 1ac6b2a..ebba7f2 100644
--- a/src/Slab/Run.hs
+++ b/src/Slab/Run.hs
@@ -45,7 +45,7 @@ run (Command.Watch srcDir renderMode passthrough distDir) =
 run (Command.Serve srcDir distDir) = Serve.run srcDir distDir
 run (Command.ReportPages srcDir) = Report.reportPages srcDir
 run (Command.ReportHeadings path) = Report.reportHeadings path
-run (Command.ReportElement i path) = Report.reportElement i path
+run (Command.ReportElement i mpath) = Report.reportElement i mpath
 run (Command.Generate path) = Generate.renderHs path
 run (Command.CommandWithPath path pmode (Command.Render Command.RenderNormal passthrough)) = do
   nodes <- executeWithMode path pmode passthrough >>= Error.unwrap
@@ -63,14 +63,14 @@ run (Command.CommandWithPath path pmode (Command.Evaluate simpl)) = do
   if simpl
     then TL.putStrLn $ pShowNoColor $ Evaluate.simplify nodes
     else TL.putStrLn $ pShowNoColor nodes
-run (Command.CommandWithPath path pmode Command.Parse) = do
-  nodes <- parseWithMode path pmode >>= Error.unwrap
+run (Command.CommandWithPath mpath pmode Command.Parse) = do
+  nodes <- parseWithMode mpath pmode >>= Error.unwrap
   TL.putStrLn $ pShowNoColor nodes
-run (Command.CommandWithPath path pmode Command.Classes) = do
-  nodes <- parseWithMode path pmode >>= Error.unwrap
+run (Command.CommandWithPath mpath pmode Command.Classes) = do
+  nodes <- parseWithMode mpath pmode >>= Error.unwrap
   mapM_ T.putStrLn $ Syntax.extractClasses nodes
-run (Command.CommandWithPath path pmode (Command.Fragments mname)) = do
-  nodes <- parseWithMode path pmode >>= Error.unwrap
+run (Command.CommandWithPath mpath pmode (Command.Fragments mname)) = do
+  nodes <- parseWithMode mpath pmode >>= Error.unwrap
   let ms = Syntax.extractFragments nodes
   case mname of
     Just name -> case Syntax.findFragment name ms of
@@ -80,49 +80,51 @@ run (Command.CommandWithPath path pmode (Command.Fragments mname)) = do
 
 --------------------------------------------------------------------------------
 parseWithMode
-  :: FilePath
+  :: (Maybe FilePath)
   -> Command.ParseMode
   -> IO (Either Error.Error [Syntax.Block])
-parseWithMode path pmode = runExceptT $ parseWithModeE path pmode
+parseWithMode mpath pmode = runExceptT $ parseWithModeE mpath pmode
 
 evaluateWithMode
-  :: FilePath
+  :: Maybe FilePath
   -> Command.ParseMode
   -> IO (Either Error.Error [Syntax.Block])
-evaluateWithMode path pmode = runExceptT $ evaluateWithModeE path pmode
+evaluateWithMode mpath pmode = runExceptT $ evaluateWithModeE mpath pmode
 
 executeWithMode
-  :: FilePath
+  :: Maybe FilePath
   -> Command.ParseMode
   -> Command.RunMode
   -> IO (Either Error.Error [Syntax.Block])
-executeWithMode path pmode passthrough = runExceptT $ executeWithModeE path pmode passthrough
+executeWithMode mpath pmode passthrough =
+  runExceptT $ executeWithModeE mpath pmode passthrough
 
 --------------------------------------------------------------------------------
 parseWithModeE
-  :: FilePath
+  :: Maybe FilePath
   -> Command.ParseMode
   -> ExceptT Error.Error IO [Syntax.Block]
-parseWithModeE path pmode =
+parseWithModeE mpath pmode =
   case pmode of
-    Command.ParseShallow -> Parse.parseFileE path
-    Command.ParseDeep -> PreProcess.preprocessFileE path
+    Command.ParseShallow -> Parse.parseFileE mpath
+    Command.ParseDeep -> PreProcess.preprocessFileE mpath
 
 evaluateWithModeE
-  :: FilePath
+  :: Maybe FilePath
   -> Command.ParseMode
   -> ExceptT Error.Error IO [Syntax.Block]
-evaluateWithModeE path pmode = do
-  parsed <- parseWithModeE path pmode
-  Evaluate.evaluate Evaluate.defaultEnv [T.pack path] parsed
+evaluateWithModeE mpath pmode = do
+  parsed <- parseWithModeE mpath pmode
+  Evaluate.evaluate Evaluate.defaultEnv [maybe "-" T.pack mpath] parsed
 
 executeWithModeE
-  :: FilePath
+  :: Maybe FilePath
   -> Command.ParseMode
   -> Command.RunMode
   -> ExceptT Error.Error IO [Syntax.Block]
-executeWithModeE path pmode passthrough =
-  evaluateWithModeE path pmode >>= Execute.execute (Execute.Context path passthrough)
+executeWithModeE mpath pmode passthrough =
+  evaluateWithModeE mpath pmode >>=
+    Execute.execute (Execute.Context mpath passthrough)
 
 --------------------------------------------------------------------------------
 -- Play with the whole language.
diff --git a/tests/Slab/Runner.hs b/tests/Slab/Runner.hs
index 888f69f..ea1367a 100644
--- a/tests/Slab/Runner.hs
+++ b/tests/Slab/Runner.hs
@@ -53,7 +53,7 @@ mkGoldenTest path = do
  where
   action :: IO Text
   action = do
-    let ctx = Execute.Context path Command.RunNormal
+    let ctx = Execute.Context (Just path) Command.RunNormal
     evaluated <- Execute.executeFile ctx
     case evaluated of
       Left _ -> pure "TODO"