Free Online Code Diff Checker
Quick answer
Paste two versions of code and see exactly what changed: a side-by-side view with aligned line numbers, added and removed counts, and a unified diff you can copy as a .patch — all computed in your browser. No signup, no upload, and both texts stay on your device the whole time.
Last updated: October 16, 2026
Code review starts with an honest answer to one question: what actually changed? This diff checker computes the answer locally, in your tab — line-level with aligned side-by-side rows, a classic unified view for patch habits, and a word-level mode for prose or compressed code. Ignore-whitespace and ignore-case switches strip away the noise that makes hand comparison useless. Nothing is transmitted: the comparison is plain JavaScript running in your browser, which means private code stays private.
Use the tool below| 1 | function greet(name) { | 1 | function greet(name: string): string { |
| 2 | var message = "Hello, " + name + "!"; | 2 | const message = `Hello, ${name}!`; |
| 3 | console.log(message); | 3 | console.log(message); |
| 4 | return message; | 4 | return message; |
| 5 | } | 5 | } |
| 6 | 6 | ||
| 7 | // TODO: add farewell | 7 | function farewell(name: string): string { |
| 8 | greet("CodeLive"); | 8 | return `Goodbye, ${name}.`; |
| 9 | } | ||
| 10 | |||
| 11 | greet("CodeLive Studio"); | ||
| 12 | farewell("CodeLive Studio"); |
Code Diff Checker runs entirely in your browser — nothing you paste or type is uploaded to any server, and no account is needed.
How do I compare two pieces of code online?
- 1
Paste the original version into the left editor and the changed version into the right — or press Sample to see a realistic before/after pair.
- 2
Watch the diff render live below: green rows are additions, red rows are deletions, and paired rows show exactly what a line became.
- 3
Switch views when useful: Side by side for aligned comparison, Unified for the classic +/- patch format, Words for word-level detail on dense edits.
- 4
Use Ignore whitespace to skip re-indentation noise, then copy the .patch text or download it as a file for use with git apply.
What this diff checker does for you
Side-by-side with aligned rows
Changed lines line up horizontally — the deleted line and its replacement sit on the same row pair, so you see transformations instead of playing spot-the-difference between two scrolling panes. Line numbers on both sides keep you oriented in the original files.
Unified view and real .patch output
The unified view is the classic +/- format every developer knows, and the Copy patch / .patch download produce a genuine unified diff with context lines — paste it into a code review, attach it to an issue, or apply it with git apply.
Word-level mode for dense edits
Long lines that differ by two tokens render as a wall of red and green in line mode. Switch to Words and the tool highlights exactly which words changed inside the line — also the right mode for comparing prose, documentation and config descriptions.
Whitespace and case are optional
Re-indentation churn drowns real changes. Ignore whitespace treats indent-only edits as equal; ignore case helps when comparing logs or generated files. Both are honest toggles, not hidden magic — the counts update to match.
Computed in your tab, never uploaded
There is no server that receives your code — the diff is calculated by a JavaScript library in your browser. Proprietary snippets, unreleased features and license keys can be compared without transmitting them to anyone.
Auto-save on both sides
Both texts persist in your browser's localStorage, so an accidental tab close or a laptop sleep does not lose the comparison you were mid-way through. No account is involved in storing anything.
CodeLive Studio vs Diffchecker.com vs GitHub diff vs VS Code
Each diff tool owns a niche. The honest comparison is where yours sits when you need a comparison right now, in a browser, without a repository or an account.
| What matters | CodeLive Studio | Diffchecker.com | GitHub diff | VS Code diff |
|---|---|---|---|---|
| Price | Free — no paid tier exists | Free tier + Pro plan | Free with account | Free app |
| Account required | Never | For some file types/history | Yes (repo needed) | No |
| Text stays in your browser | Yes — computed client-side | Sent to their servers | Stored in the repo | Local only |
| Works without a repository | Yes | Yes | No | Yes |
| Side-by-side view | Yes, aligned rows | Yes | Yes | Yes |
| Word-level diff | Yes, built in | Pro feature | Per-line only | Yes |
| Export unified .patch | Copy or download, free | Pro-gated exports | Yes (as commits) | Via git |
| Images / PDF / Excel compare | No — text and code focus | Yes (Pro for some) | Limited | With extensions |
Based on publicly available information as of October 2026 — plans change, so verify on each site if a detail is critical. Honest footnote: Diffchecker's paid tiers add file-type comparisons (images, PDFs, Excel) that this tool deliberately does not attempt; VS Code with a repo open is the gold standard for local reviewing. This page owns the browser-only, no-account, private-text niche.
How does a line-level diff actually work?
The tool uses the Myers diff algorithm — the same algorithm family behind git diff. It computes the shortest edit script that transforms the original into the changed text: a sequence of keep, insert and delete operations. Grouping those operations produces the blocks you see: unchanged context, deletions, additions, and paired delete/insert rows where lines were edited rather than removed and re-typed.
That is why the diff is trustworthy in both directions: nothing is highlighted that has not actually changed, and nothing changed goes unhighlighted. The word-level mode applies the same algorithm one level down — tokenizing lines into words and diffing those — which is what makes it the right mode for prose and minimally-edited dense lines.
When is a browser diff checker the right tool?
Whenever the two texts exist but the workflow does not: a snippet a colleague pasted into chat, a config file from two different servers, a paragraph before and after an edit, a stack trace compared line by line, or homework versions you want to check before submitting. Setting up a git repo or copying files into an IDE for these is overhead the task does not deserve.
It is also the privacy-safe choice for code you cannot paste into third-party services — unreleased work under NDA, license-key logic, internal tooling. Because the comparison is computed in your browser with no upload path, the network tab stays empty no matter what you paste. When you do have a repository, git's diff remains the better tool; this page covers everywhere git is not.
Questions this tool answers
- code diff checker
- online diff checker
- compare two files online
- text diff tool
- diff checker free no signup
Frequently asked questions
Is this code diff checker free?
Yes — side-by-side, unified and word views, whitespace options and .patch export are all free with no account and no limits. The comparison runs on your machine, so there are no per-comparison server costs behind a paywall.
Is my code uploaded when I compare two versions?
No. The diff is computed by JavaScript inside your browser tab and nothing is transmitted — there is no backend on this page to receive text. Your inputs are only stored in your own browser's localStorage between visits.
Can I use this for text and documents, not just code?
Yes — switch to the Words view and paste prose: it highlights changed words inline, which is ideal for editing copy, comparing contract revisions or checking what an AI rewrite actually altered. Line mode suits code and structured files.
How large a file can the diff handle?
Thousands of lines compare fine; beyond about 3,000 diff rows the inline rendering pauses to keep the page responsive — but the unified patch export still works at full size, so you can copy or download the complete diff either way.
What is the .patch file for?
It is a standard unified diff with three lines of context — the same format git produces and accepts. Save it with the .patch button and apply it elsewhere with git apply, share it in a bug report, or archive it as a minimal record of what changed.
How do I ignore indentation-only changes?
Enable Ignore whitespace — lines that differ only in leading or trailing spaces are treated as equal, which removes the noise from re-indented blocks and lets the real edits surface. Ignore case works the same way for letter-case-only differences.
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