Diff & Patch Generator

Create unified diff patches online — compare two texts into a .patch file with configurable context, or apply a patch back (even reverse). GNU patch compatible format.

Old file nameNew file nameContext lines

Original text

function greet(name) {
  const msg = "hello " + name;
  console.log(msg);
  return msg;
}

Unified diff output

--- a.txt
+++ b.txt
@@ -1,5 +1,5 @@
 function greet(name) {
-  const msg = "hello " + name;
+  const msg = `Hello, ${name}!`;
   console.log(msg);
-  return msg;
+  return msg.trim();
 }
\ No newline at end of file

About Diff & Patch Generator

Paste the original and modified text to get a standard unified diff — ---/+++ headers, @@ hunks with configurable context lines, "No newline at end of file" markers — ready to feed to git apply or GNU patch.

Flip the direction and apply a pasted patch to a source text: hunks are verified against context with an offset search like real patch, failures are reported per hunk, and reverse mode undoes a patch. Everything runs locally in your browser.