diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,25 @@
 # Changelog
 
+## 0.15.1.0 (2025-04-26)
+
+ *  Add a `syntax` option for `eval` blocks (#187).  This allows you to set
+    the syntax highlighting to be used for the _output of the evaluated code_,
+    for example:
+
+        ---
+        patat:
+          eval:
+            ruby:
+              command: irb --noecho --noverbose
+              syntax: json
+        ...
+
+        Here is a code block:
+
+        ```ruby
+        puts '{"hello": "world"}'
+        ```
+
 ## 0.15.0.0 (2025-04-05)
 
  *  Add [OSC8] support for hyperlinks (#185).  This makes hyperlinks clickable
diff --git a/README.md b/README.md
--- a/README.md
+++ b/README.md
@@ -719,12 +719,13 @@
           reveal: true  # Optional
           replace: false  # Optional
           container: code  # Optional
+          syntax: json  # Optional
     ...
 
     Here is an example of a code block that is evaluated:
 
     ```ruby
-    puts "Hi"
+    puts '{"hello": "world"}'
     ```
 
 An arbitrary amount of evaluators can be specified, and whenever a a class
@@ -734,7 +735,7 @@
 code of presentations downloaded from the internet before running them if they
 contain `eval` settings.
 
-Aside from the command, there are four more options:
+Aside from the command, there are five more options:
 
  -  `reveal`: Introduce a pause (see [fragments](#fragmented-slides)) in
     between showing the original code block and the output.  Defaults to `true`.
@@ -746,11 +747,41 @@
      *  `code`: the default setting.
      *  `none`: no formatting applied.
      *  `inline`: no formatting applied and no trailing newline.
+ -  `syntax`: When using `container: code` (the default), the output of the eval
+    block will use the same syntax highlighting as the input code block.
+    You can customize this using `syntax`, e.g. `syntax: json`.
  -  `stderr`: Include output from standard error.  Defaults to `true`.
+
  -  `wrap`: this is a deprecated name for `container`, used in version 0.11 and
     earlier.
  -  `fragment`: this is a deprecated name for `reveal`, used in version 0.13 and
     earlier.
+
+Note that it is possible to set multiple classes on a codeblock by using pandoc
+fenced code block syntax.  This allows you to to separate syntax highlighting
+from evaluation.  You can use this to only evaluate certain snippets, or even
+evaluate using different commands or settings:
+
+    ---
+    patat:
+      eval:
+        python2:
+          command: python2
+        python3:
+          command: python3
+    ...
+
+    Snippet evaluated using an old python version:
+
+    ~~~{.python .python2}
+    print "Hello, world"
+    ~~~
+
+    Snippet evaluated using a more recent python version:
+
+    ~~~{.python .python3}
+    print("Hello, world")
+    ~~~
 
 Setting `reveal: false` and `replace: true` offers a way to "filter" code
 blocks, which can be used to render ASCII graphics.
diff --git a/lib/Patat/Eval/Internal.hs b/lib/Patat/Eval/Internal.hs
--- a/lib/Patat/Eval/Internal.hs
+++ b/lib/Patat/Eval/Internal.hs
@@ -33,8 +33,14 @@
 --------------------------------------------------------------------------------
 renderEvalBlock :: EvalBlock -> T.Text -> [Block]
 renderEvalBlock EvalBlock {..} out = case evalContainer ebSettings of
-    EvalContainerCode   -> [CodeBlock ebAttr out]
+    EvalContainerCode   -> [CodeBlock ("", classes, []) out]
     EvalContainerNone   -> [RawBlock fmt out]
     EvalContainerInline -> [Plain [RawInline fmt out]]
   where
     fmt = "eval"
+
+    -- The classes for the new code block are copied from the old one if
+    -- unspecified, or the syntax specified in the eval settings.
+    classes = case evalSyntax ebSettings of
+        Nothing        -> let (_, cs, _) = ebAttr in cs
+        Just outSyntax -> [outSyntax]
diff --git a/lib/Patat/Presentation/Settings.hs b/lib/Patat/Presentation/Settings.hs
--- a/lib/Patat/Presentation/Settings.hs
+++ b/lib/Patat/Presentation/Settings.hs
@@ -257,6 +257,7 @@
     , evalReveal    :: !Bool
     , evalContainer :: !EvalSettingsContainer
     , evalStderr    :: !Bool
+    , evalSyntax    :: !(Maybe T.Text)
     } deriving (Eq, Show)
 
 
@@ -268,6 +269,7 @@
         <*> deprecated "fragment" "reveal" True o
         <*> deprecated "wrap" "container" EvalContainerCode o
         <*> o A..:? "stderr" A..!= True
+        <*> o A..:? "syntax"
       where
         deprecated old new def obj = do
             mo <- obj A..:? old
diff --git a/patat.cabal b/patat.cabal
--- a/patat.cabal
+++ b/patat.cabal
@@ -1,5 +1,5 @@
 Name:          patat
-Version:       0.15.0.0
+Version:       0.15.1.0
 Synopsis:      Terminal-based presentations using Pandoc
 Description:   Terminal-based presentations using Pandoc.
 License:       GPL-2