Code Diff Checker

What is a code diff checker?

A diff checker compares two versions of a file and shows exactly what changed between them: lines that were added, removed or modified. It is the same idea as git diff or a pull-request review, without needing a repository — paste two snippets, drop two files, and see the changes instantly.

This diff tool, CodeDiff Studio, goes further than a plain line comparison. Modified lines are paired up and the exact words or characters that changed inside them are highlighted, syntax highlighting makes the code readable, and noise filters let you ignore whitespace, letter case, blank lines or comments so that a reformatted file does not hide the one real change.

When to use an online diff tool

• Reviewing a change outside Git — config files copied from a server, SQL from a ticket, snippets from Slack or Stack Overflow.
• Comparing environments — .env templates, nginx or Apache configs, Kubernetes manifests and Terraform plans between staging and production.
• Debugging API responses — paste two payloads to spot the field that changed (for structured JSON, the JSON Diff tool ignores key order and reports exact paths).
• Checking a refactor or formatter — turn on “Hide whitespace changes” to confirm Prettier, Black or PHP-CS-Fixer only touched formatting.
• Sharing a review — export a .diff patch or create a share link for a teammate.

Split view vs. unified view

Split view places the original and modified versions side by side with aligned line numbers — the easiest way to read larger edits. Unified view shows a single column, the format used by git diff, diff -u and patch files:

--- original.js
+++ modified.js
@@ -1,4 +1,4 @@
 const client = createClient({
-  timeout: 5000,
+  timeout: 10000,
   retries: 3,
 })

Lines starting with - were removed, lines starting with + were added, and the @@ header gives the line ranges in each file. An exported patch can be applied with git apply changes.diff or patch -p0 < changes.diff.

Private by design

The comparison engine runs in your browser. Your code is never uploaded to ProWebLook, saved comparisons stay in this browser’s local storage, and share links carry the content in the URL fragment (the part after #), which browsers do not send to servers. Anyone you give a share link to can read its contents, so treat it like the code itself.

Keyboard shortcuts: press E to switch between editing and the comparison, Ctrl/⌘ + Enter to apply edits, and Ctrl/⌘ + S to save a comparison while the tool has focus.