diff --git a/analysis/src/Cli.ml b/analysis/src/Cli.ml
index a49326d92..7e0f1bb77 100644
--- a/analysis/src/Cli.ml
+++ b/analysis/src/Cli.ml
@@ -10,6 +10,7 @@ API examples:
   ./rescript-editor-analysis.exe hover src/MyFile.res 10 2
   ./rescript-editor-analysis.exe references src/MyFile.res 10 2
   ./rescript-editor-analysis.exe rename src/MyFile.res 10 2 foo
+  ./rescript-editor-analysis.exe diagnosticSyntax src/MyFile.res
 
 Dev-time examples:
   ./rescript-editor-analysis.exe dump src/MyFile.res src/MyFile2.res
@@ -60,6 +61,10 @@ Options:
 
     ./rescript-editor-analysis.exe format src/MyFile.res
 
+  diagnosticSyntax: print to stdout diagnostic for syntax
+
+    ./rescript-editor-analysis.exe diagnosticSyntax src/MyFile.res
+
   test: run tests specified by special comments in file src/MyFile.res
 
     ./rescript-editor-analysis.exe test src/src/MyFile.res
@@ -88,6 +93,8 @@ let main () =
     Commands.codeAction ~path
       ~pos:(int_of_string line, int_of_string col)
       ~currentFile ~debug:false
+  | [_; "diagnosticSyntax"; path;] -> 
+    Commands.diagnosticSyntax ~path
   | _ :: "reanalyze" :: _ ->
     let len = Array.length Sys.argv in
     for i = 1 to len - 2 do
diff --git a/analysis/src/Commands.ml b/analysis/src/Commands.ml
index 65066f8a8..48c4d6338 100644
--- a/analysis/src/Commands.ml
+++ b/analysis/src/Commands.ml
@@ -257,6 +257,10 @@ let format ~path =
         signature
   else ""
 
+let diagnosticSyntax ~path =
+  print_endline
+    (Diagnostics.document_syntax ~path |> Protocol.array)
+
 let test ~path =
   Uri.stripPath := true;
   match Files.readFile path with
@@ -378,6 +382,7 @@ let test ~path =
                                  Printf.printf "%s\nnewText:\n%s<--here\n%s%s\n"
                                    (Protocol.stringifyRange range)
                                    indent indent newText)))
+          | "dia" -> diagnosticSyntax ~path
           | _ -> ());
           print_newline ())
     in
diff --git a/analysis/src/Diagnostics.ml b/analysis/src/Diagnostics.ml
new file mode 100644
index 000000000..5ef3673dd
--- /dev/null
+++ b/analysis/src/Diagnostics.ml
@@ -0,0 +1,33 @@
+let document_syntax ~path =
+  let get_diagnostics diagnostics =
+    diagnostics
+    |> List.map (fun diagnostic ->
+           let _, startline, startcol =
+             Location.get_pos_info (Res_diagnostics.getStartPos diagnostic)
+           in
+           let _, endline, endcol =
+             Location.get_pos_info (Res_diagnostics.getEndPos diagnostic)
+           in
+           Protocol.stringifyDiagnostic
+             {
+               range =
+                 {
+                   start = {line = startline - 1; character = startcol};
+                   end_ = {line = endline - 1; character = endcol};
+                 };
+               message = Res_diagnostics.explain diagnostic;
+               severity = 1;
+             })
+  in
+  if FindFiles.isImplementation path then
+    let parseImplementation =
+      Res_driver.parsingEngine.parseImplementation ~forPrinter:false
+        ~filename:path
+    in
+    get_diagnostics parseImplementation.diagnostics
+  else if FindFiles.isInterface path then
+    let parseInterface =
+      Res_driver.parsingEngine.parseInterface ~forPrinter:false ~filename:path
+    in
+    get_diagnostics parseInterface.diagnostics
+  else []
\ No newline at end of file
diff --git a/analysis/src/Protocol.ml b/analysis/src/Protocol.ml
index 076137842..4a03b1508 100644
--- a/analysis/src/Protocol.ml
+++ b/analysis/src/Protocol.ml
@@ -10,11 +10,16 @@ type completionItem = {
   documentation: markupContent option;
 }
 
-type hover = string
-type location = {uri: string; range: range}
-type documentSymbolItem = {name: string; kind: int; location: location}
-type renameFile = {oldUri: string; newUri: string}
-type textEdit = {range: range; newText: string}
+type location = {uri : string; range : range}
+type documentSymbolItem = {name : string; kind : int; location : location}
+type renameFile = {oldUri : string; newUri : string}
+type textEdit = {range : range; newText : string}
+
+type diagnostic = {
+  range : range;
+  message : string;
+  severity : int;
+}
 
 type optionalVersionedTextDocumentIdentifier = {
   version: int option;
@@ -89,7 +94,7 @@ let stringifyRenameFile {oldUri; newUri} =
 }|}
     (Json.escape oldUri) (Json.escape newUri)
 
-let stringifyTextEdit te =
+let stringifyTextEdit (te : textEdit) =
   Printf.sprintf {|{
   "range": %s,
   "newText": "%s"
@@ -126,3 +131,14 @@ let stringifyCodeAction ca =
   Printf.sprintf {|{"title": "%s", "kind": "%s", "edit": %s}|} ca.title
     (codeActionKindToString ca.codeActionKind)
     (ca.edit |> stringifyCodeActionEdit)
+
+(* https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#diagnostic *)
+let stringifyDiagnostic d =
+  Printf.sprintf {|{
+  "range": %s,
+  "message": "%s",
+  "severity": %d,
+  "source": "ReScript"
+}|}
+    (stringifyRange d.range) (Json.escape d.message)
+    d.severity
\ No newline at end of file
diff --git a/analysis/tests/not_compiled/Diagnostics.res b/analysis/tests/not_compiled/Diagnostics.res
new file mode 100644
index 000000000..c81f1e63e
--- /dev/null
+++ b/analysis/tests/not_compiled/Diagnostics.res
@@ -0,0 +1,5 @@
+let = 1 + 1.0
+let add = =2
+lett a = 2
+
+//^dia
\ No newline at end of file
diff --git a/analysis/tests/not_compiled/expected/Diagnostics.res.txt b/analysis/tests/not_compiled/expected/Diagnostics.res.txt
new file mode 100644
index 000000000..a5df33b71
--- /dev/null
+++ b/analysis/tests/not_compiled/expected/Diagnostics.res.txt
@@ -0,0 +1,17 @@
+[{
+  "range": {"start": {"line": 2, "character": 4}, "end": {"line": 2, "character": 6}},
+  "message": "consecutive statements on a line must be separated by ';' or a newline",
+  "severity": 1,
+  "source": "ReScript"
+}, {
+  "range": {"start": {"line": 1, "character": 9}, "end": {"line": 1, "character": 11}},
+  "message": "This let-binding misses an expression",
+  "severity": 1,
+  "source": "ReScript"
+}, {
+  "range": {"start": {"line": 0, "character": 4}, "end": {"line": 0, "character": 5}},
+  "message": "I was expecting a name for this let-binding. Example: `let message = \"hello\"`",
+  "severity": 1,
+  "source": "ReScript"
+}]
+
diff --git a/analysis/tests/test.sh b/analysis/tests/test.sh
index 27a98ffb2..c931641e9 100755
--- a/analysis/tests/test.sh
+++ b/analysis/tests/test.sh
@@ -7,6 +7,15 @@ for file in src/*.{res,resi}; do
   fi
 done
 
+for file in not_compiled/*.res; do
+  output="$(dirname $file)/expected/$(basename $file).txt"
+  ../rescript-editor-analysis.exe test $file &> $output
+  # CI. We use LF, and the CI OCaml fork prints CRLF. Convert.
+  if [ "$RUNNER_OS" == "Windows" ]; then
+    perl -pi -e 's/\r\n/\n/g' -- $output
+  fi
+done
+
 warningYellow='\033[0;33m'
 successGreen='\033[0;32m'
 reset='\033[0m'
diff --git a/server/src/server.ts b/server/src/server.ts
index c5683387b..f99ac82d3 100644
--- a/server/src/server.ts
+++ b/server/src/server.ts
@@ -57,7 +57,7 @@ let projectsFiles: Map<
 let codeActionsFromDiagnostics: codeActions.filesCodeActions = {};
 
 // will be properly defined later depending on the mode (stdio/node-rpc)
-let send: (msg: p.Message) => void = (_) => {};
+let send: (msg: p.Message) => void = (_) => { };
 
 interface CreateInterfaceRequestParams {
   uri: string;
@@ -598,6 +598,34 @@ function format(msg: p.RequestMessage): Array<p.Message> {
   }
 }
 
+const updateDiagnosticSyntax = (fileUri: string, fileContent: string) => {
+  let filePath = fileURLToPath(fileUri);
+  let extension = path.extname(filePath);
+  let tmpname = utils.createFileInTempDir(extension);
+  fs.writeFileSync(tmpname, fileContent, { encoding: "utf-8" });
+
+  const items: p.Diagnostic[] | [] = utils.runAnalysisAfterSanityCheck(
+    filePath,
+    [
+      "diagnosticSyntax",
+      tmpname
+    ],
+  );
+
+  const notification: p.NotificationMessage = {
+    jsonrpc: c.jsonrpcVersion,
+    method: "textDocument/publishDiagnostics",
+    params: {
+      uri: fileUri,
+      diagnostics: items
+    }
+  }
+
+  fs.unlink(tmpname, () => null);
+
+  send(notification)
+}
+
 function createInterface(msg: p.RequestMessage): p.Message {
   let params = msg.params as CreateInterfaceRequestParams;
   let extension = path.extname(params.uri);
@@ -784,6 +812,7 @@ function onMessage(msg: p.Message) {
     } else if (msg.method === DidOpenTextDocumentNotification.method) {
       let params = msg.params as p.DidOpenTextDocumentParams;
       openedFile(params.textDocument.uri, params.textDocument.text);
+      updateDiagnosticSyntax(params.textDocument.uri, params.textDocument.text);
     } else if (msg.method === DidChangeTextDocumentNotification.method) {
       let params = msg.params as p.DidChangeTextDocumentParams;
       let extName = path.extname(params.textDocument.uri);
@@ -797,6 +826,7 @@ function onMessage(msg: p.Message) {
             params.textDocument.uri,
             changes[changes.length - 1].text
           );
+          updateDiagnosticSyntax(params.textDocument.uri, changes[changes.length - 1].text);
         }
       }
     } else if (msg.method === DidCloseTextDocumentNotification.method) {
diff --git a/server/src/utils.ts b/server/src/utils.ts
index c3176697c..c67fb5fd7 100644
--- a/server/src/utils.ts
+++ b/server/src/utils.ts
@@ -603,9 +603,9 @@ export let parseCompilerLogOutput = (
       //   10 ┆
     } else if (line.startsWith("  ")) {
       // part of the actual diagnostics message
-      parsedDiagnostics[parsedDiagnostics.length - 1].content.push(
-        line.slice(2)
-      );
+        parsedDiagnostics[parsedDiagnostics.length - 1].content.push(
+          line.slice(2)
+        );
     } else if (line.trim() != "") {
       // We'll assume that everything else is also part of the diagnostics too.
       // Most of these should have been indented 2 spaces; sadly, some of them
@@ -635,7 +635,7 @@ export let parseCompilerLogOutput = (
       range,
       source: "ReScript",
       // remove start and end whitespaces/newlines
-      message: diagnosticMessage.join("\n").trim() + "\n",
+      message: diagnosticMessage.join("\n").trim(),
     };
 
     // Check for potential code actions