Zero Snippet

Code diff checker — side-by-side compare for snippets, configs, and reviews

Use this free online code diff tool to compare two text or code versions in a side-by-side diff view: unchanged lines stay aligned, removed lines highlight on the left, and added lines highlight on the right—a lightweight pull-request-style readout without cloning a repo. Processing is client-side only, so drafts and proprietary snippets stay in your browser. When you need readable inputs first, normalize JSON with our JSON formatter & validator, markup with the HTML formatter & minifier, or queries with the SQL formatter before you diff.

9 lines

9 lines

6 unchanged−3 removed+3 added

Original
Modified
1function greet(name) {
2 if (!name) {
1function greet(name: string): string {
2 if (!name?.trim()) {
3 return "Hello";3 return "Hello";
4 }4 }
5 return "Hello, " + name;
5 return `Hello, ${name}`;
6}6}
77
8export { greet };8export { greet };
99

Comparison is line-based (not character-by-character). Normalize formatting with our formatters first if whitespace-only changes should disappear. For version-controlled projects, Git remains the source of truth for merges and blame.

Why use a browser-based code diff checker?

Engineers and technical writers constantly juggle before/after snippets: support emails, Slack threads, CI logs, and CMS drafts rarely arrive as a tidy Git branch. A dedicated paste-and-compare diff answers “what changed between these two blocks?” in seconds. It complements—not replaces—git diff, merge tools, and IDE reviewers when you only have raw text. Because this page never uploads your buffers, you can sanity-check internal APIs, Terraform snippets, or redacted logs on a locked-down machine.

Teams reviewing configuration drift often pair a diff view with encoders and parsers: validate tokens using the JWT decoder, normalize YAML via YAML to JSON, and keep CSV-shaped samples consistent through CSV to JSON before lining up versions here.

How to use this code diff checker (step by step)

  1. Paste the original text into the left editor—the “old” file fragment, baseline policy, or message you received. Click Load sample to preview a small TypeScript-style refactor.
  2. Paste the modified text into the right editor. The tool splits on line breaks, so one long minified line will diff as a single row; run the JavaScript formatter & minifier or CSS formatter & minifier when you need wrapped lines for review.
  3. Read the side-by-side table: line numbers restart per column, blank mates mark insertions or deletions, and the summary counts call out how many rows were kept, removed, or added.
  4. Optional: click Copy unified diff to grab a compact -/+/ text block for tickets or documentation. Clear both fields when you move to the next pair.

Keywords and workflows teams search for

People look for an online text diff, code compare tool, line-by-line diff viewer, or paste diff for code review when they need fast answers outside Git. Content and growth engineers diff JSON-LD or meta blocks after edits—cross-check live pages with the meta tags extractor once structural tags change. Security reviewers compare redacted headers or payloads alongside the HTTP header checker when validating responses.

Line-based diffing vs character-level and semantic tools

This checker aligns whole lines using a classic longest common subsequence strategy. That keeps the implementation predictable and fast for typical snippets, but a tiny edit in a 400-character line will show as a full-line removal and addition. Semantic or word-level diffs inside IDEs can look prettier for prose; use those when wording matters more than structure. When you debug extraction or rewrite rules, the regex tester & debugger still wins for pattern-level inspection.

Privacy, limits, and when to stay in Git

Nothing leaves your tab during comparison, which helps regulated teams and consultants working on NDA code. Each side caps at a few thousand lines to protect memory—slice functions or modules for megafiles. For merges, blame, and history, continue using Git; for binary assets, use dedicated viewers. If you need structured document conversion before diffing, try HTML to Markdown or Markdown to HTML to align formats first.

Related developer tools

Explore the full code and developer tools catalog. Highlights:

  • JSON Formatter & Validator — Format, validate, minify, and explore JSON in a collapsible tree—fix payloads before they hit production.
  • JSON to CSV Converter — Turn JSON arrays into downloadable CSV with automatic column detection for spreadsheets and BI tools.
  • JSON to YAML Converter — Convert JSON to readable YAML for configs and Kubernetes—copy or download the result.
  • CSV to JSON Converter — Paste or upload CSV and get structured JSON with header-aware typing for APIs and apps.
  • YAML to JSON Converter — Parse YAML to valid JSON with clear errors—ideal for CI configs and cloud templates.
  • XML Formatter & Validator — Beautify and validate XML with structure insight and actionable parse errors.
  • Regex Tester & Debugger — Test patterns live with highlights, capture groups, and flags—debug regex without leaving the browser.
  • SQL Formatter — Pretty-print SQL with indentation and keyword casing for readable queries and code review.
  • HTML Formatter & Minifier — Beautify or minify HTML and compare raw markup with a quick rendered preview.
  • CSS Formatter & Minifier — Format messy stylesheets or minify CSS for faster loads—keep design tokens consistent.
  • JavaScript Formatter & Minifier — Pretty-print or minify JavaScript for debugging locally and shipping smaller bundles.
  • HTML to Markdown Converter — Convert HTML snippets to Markdown for docs, CMS migrations, and README cleanup.
  • Markdown to HTML Converter — Turn Markdown into HTML with a live preview—handy for emails, blogs, and static pages.
  • JWT Decoder — Decode JWT header and payload and check expiry—signature verification not included, client-side safe.

Frequently asked questions

What does this code diff checker do?
Paste an original and a revised code block to see a line-by-line comparison. Unchanged lines appear in both columns, removed lines highlight on the left, and new lines highlight on the right—similar to a focused pull-request view. All comparison runs locally in your browser.
Is my source code uploaded to your servers?
No. The diff is computed with JavaScript in your tab only. Nothing you paste is sent to our backend unless you use another tool on this site that explicitly performs network requests.
Why do my diffs look noisy when I only reordered lines?
This tool uses a line-based longest-common-subsequence alignment. Reordering can show many deletions and insertions even when the text is the same, because order matters. For reorder-heavy edits, use your Git client or a semantic diff tool; use this page for quick paste-and-compare reviews.
Is there a maximum file size?
Each side is limited to roughly two thousand lines to keep memory and rendering responsive in the browser. For very large repositories, compare slices (one function or file at a time) or rely on git diff locally.
Does this understand syntax inside a line?
No. Comparison is line-based, not character- or token-based. A single-character change on a long line marks that line as removed and added as a whole. For fine-grained regex or string work, pair this with the regex tester and debugger in our developer tools catalog.
How is this different from git diff or my IDE?
Git and editors integrate with version control, hunks, merges, and blame. This page is a fast, install-free scratchpad when you have two snippets from a ticket, email, or log—no repository required. For formatted JSON or YAML configs, you may still want the JSON formatter or YAML to JSON converter before diffing.
Can I compare JSON, YAML, or Markdown?
Yes, as plain text. Normalize formatting first if you care about whitespace: use the JSON formatter, XML formatter, SQL formatter, or Markdown to HTML converter where applicable, then paste both versions here for a cleaner diff.
Which related tools should I use next?
Pretty-print payloads with the JSON formatter and validator, clean markup with the HTML formatter and minifier, test patterns with the regex tester, decode tokens with the JWT decoder, and browse the full code and developer tools section on the home page for encoders, hash tools, and more.