diff --git a/src/compiler/crystal/tools/doc/constant.cr b/src/compiler/crystal/tools/doc/constant.cr
index c3a7a0be0c32..e14d34455f9c 100644
--- a/src/compiler/crystal/tools/doc/constant.cr
+++ b/src/compiler/crystal/tools/doc/constant.cr
@@ -24,4 +24,12 @@ class Crystal::Doc::Constant
   def formatted_value
     Highlighter.highlight value.to_s
   end
+
+  def to_json(builder : JSON::Builder)
+    builder.object do
+      builder.field "value", value.try(&.to_s)
+      builder.field "doc", doc
+      builder.field "summary", formatted_summary
+    end
+  end
 end
diff --git a/src/compiler/crystal/tools/doc/generator.cr b/src/compiler/crystal/tools/doc/generator.cr
index 482d1f809ba4..adf303d9f3dc 100644
--- a/src/compiler/crystal/tools/doc/generator.cr
+++ b/src/compiler/crystal/tools/doc/generator.cr
@@ -67,12 +67,17 @@ class Crystal::Doc::Generator
     end
 
     if filename
-      body = doc(program_type, File.read(filename))
+      raw_body = File.read(filename)
+      body = doc(program_type, raw_body)
     else
+      raw_body = ""
       body = ""
     end
 
     File.write File.join(@output_dir, "index.html"), MainTemplate.new(body, types, repository_name)
+
+    main_index = Main.new(raw_body, Type.new(self, @program), repository_name)
+    File.write File.join(@output_dir, "index.json"), main_index
   end
 
   def copy_files
@@ -350,7 +355,15 @@ class Crystal::Doc::Generator
     filename[@base_dir.size..-1]
   end
 
-  record RelativeLocation, filename : String, line_number : Int32, url : String?
+  record RelativeLocation, filename : String, line_number : Int32, url : String? do
+    def to_json(builder : JSON::Builder)
+      builder.object do
+        builder.field "filename", filename
+        builder.field "line_number", line_number
+        builder.field "url", url
+      end
+    end
+  end
   SRC_SEP = "src#{File::SEPARATOR}"
 
   def relative_locations(type)
diff --git a/src/compiler/crystal/tools/doc/macro.cr b/src/compiler/crystal/tools/doc/macro.cr
index 00dc9a319faf..d3af7c4848e1 100644
--- a/src/compiler/crystal/tools/doc/macro.cr
+++ b/src/compiler/crystal/tools/doc/macro.cr
@@ -92,4 +92,19 @@ class Crystal::Doc::Macro
   def must_be_included?
     @generator.must_include? @macro
   end
+
+  def to_json(builder : JSON::Builder)
+    builder.object do
+      builder.field "id", id
+      builder.field "html_id", html_id
+      builder.field "name", name
+      builder.field "doc", doc
+      builder.field "summary", formatted_summary
+      builder.field "abstract", abstract?
+      builder.field "args", args
+      builder.field "args_string", args_to_s
+      builder.field "source_link", source_link
+      builder.field "def", self.macro
+    end
+  end
 end
diff --git a/src/compiler/crystal/tools/doc/main.cr b/src/compiler/crystal/tools/doc/main.cr
new file mode 100644
index 000000000000..a7ab92bd2ae2
--- /dev/null
+++ b/src/compiler/crystal/tools/doc/main.cr
@@ -0,0 +1,15 @@
+module Crystal::Doc
+  record Main, body : String, program : Type, repository_name : String do
+    def to_s(io : IO)
+      to_json(io)
+    end
+
+    def to_json(builder : JSON::Builder)
+      builder.object do
+        builder.field "repository_name", repository_name
+        builder.field "body", body
+        builder.field "program", program
+      end
+    end
+  end
+end
diff --git a/src/compiler/crystal/tools/doc/method.cr b/src/compiler/crystal/tools/doc/method.cr
index 70b5bf7a238a..5b9b9e250ba1 100644
--- a/src/compiler/crystal/tools/doc/method.cr
+++ b/src/compiler/crystal/tools/doc/method.cr
@@ -202,4 +202,20 @@ class Crystal::Doc::Method
   def has_args?
     !@def.args.empty? || @def.block_arg || @def.yields
   end
+
+  def to_json(builder : JSON::Builder)
+    builder.object do
+      builder.field "id", id
+      builder.field "html_id", html_id
+      builder.field "name", name
+      builder.field "doc", doc
+      builder.field "summary", formatted_summary
+      builder.field "abstract", abstract?
+      builder.field "args", args
+      builder.field "args_string", args_to_s
+      builder.field "source_link", source_link
+      builder.field "source_link", source_link
+      builder.field "def", self.def
+    end
+  end
 end
diff --git a/src/compiler/crystal/tools/doc/to_json.cr b/src/compiler/crystal/tools/doc/to_json.cr
new file mode 100644
index 000000000000..32c42712c1ca
--- /dev/null
+++ b/src/compiler/crystal/tools/doc/to_json.cr
@@ -0,0 +1,41 @@
+class Crystal::Arg
+  def to_json(builder : JSON::Builder)
+    builder.object do
+      builder.field "name", name
+      builder.field "doc", doc
+      builder.field "default_value", default_value.to_s
+      builder.field "external_name", external_name.to_s
+      builder.field "restriction", restriction.to_s
+    end
+  end
+end
+
+class Crystal::Def
+  def to_json(builder : JSON::Builder)
+    builder.object do
+      builder.field "name", name
+      builder.field "args", args
+      builder.field "double_splat", double_splat
+      builder.field "splat_index", splat_index
+      builder.field "yields", yields
+      builder.field "block_arg", block_arg
+      builder.field "return_type", return_type.to_s
+      builder.field "visibility", visibility.to_s
+      builder.field "body", body.to_s
+    end
+  end
+end
+
+class Crystal::Macro
+  def to_json(builder : JSON::Builder)
+    builder.object do
+      builder.field "name", name
+      builder.field "args", args
+      builder.field "double_splat", double_splat
+      builder.field "splat_index", splat_index
+      builder.field "block_arg", block_arg
+      builder.field "visibility", visibility.to_s
+      builder.field "body", body.to_s
+    end
+  end
+end
diff --git a/src/compiler/crystal/tools/doc/type.cr b/src/compiler/crystal/tools/doc/type.cr
index 608160f30261..d5af4895e49e 100644
--- a/src/compiler/crystal/tools/doc/type.cr
+++ b/src/compiler/crystal/tools/doc/type.cr
@@ -134,12 +134,12 @@ class Crystal::Doc::Type
   end
 
   def alias_definition
-    alias_def = @type.as(AliasType).aliased_type
+    alias_def = @type.as?(AliasType).try(&.aliased_type)
     alias_def
   end
 
   def formatted_alias_definition
-    type_to_html alias_definition
+    type_to_html alias_definition.as(Crystal::Type)
   end
 
   @types : Array(Type)?
@@ -772,4 +772,66 @@ class Crystal::Doc::Type
   end
 
   delegate to_s, inspect, to: @type
+
+  def to_json(builder : JSON::Builder)
+    builder.object do
+      builder.field "html_id", html_id
+      builder.field "path", path
+      builder.field "kind", kind
+      builder.field "full_name", full_name
+      builder.field "name", name
+      builder.field "abstract", abstract?
+      builder.field "superclass" { superclass.try(&.to_json_simple(builder)) || builder.scalar(nil) }
+      builder.field "ancestors" do
+        builder.array do
+          ancestors.each &.to_json_simple(builder)
+        end
+      end
+      builder.field "locations", locations
+      builder.field "repository_name", repository_name
+      builder.field "program", program?
+      builder.field "enum", enum?
+      builder.field "alias", alias?
+      builder.field "aliased", alias_definition.to_s
+      builder.field "const", const?
+      builder.field "constants", constants
+      builder.field "included_modules" do
+        builder.array do
+          included_modules.each &.to_json_simple(builder)
+        end
+      end
+      builder.field "extended_modules" do
+        builder.array do
+          extended_modules.each &.to_json_simple(builder)
+        end
+      end
+      builder.field "subclasses" do
+        builder.array do
+          subclasses.each &.to_json_simple(builder)
+        end
+      end
+      builder.field "including_types" do
+        builder.array do
+          including_types.each &.to_json_simple(builder)
+        end
+      end
+      builder.field "namespace" { namespace.try(&.to_json_simple(builder)) || builder.scalar(nil) }
+      builder.field "doc", doc
+      builder.field "summary", formatted_summary
+      builder.field "class_methods", class_methods
+      builder.field "constructors", constructors
+      builder.field "instance_methods", instance_methods
+      builder.field "macros", macros
+      builder.field "types", types
+    end
+  end
+
+  def to_json_simple(builder : JSON::Builder)
+    builder.object do
+      builder.field "html_id", html_id
+      builder.field "kind", kind
+      builder.field "full_name", full_name
+      builder.field "name", name
+    end
+  end
 end