Online Diff Checker — Compare Text Instantly
Quick answer
This online diff checker compares two texts the moment you paste them: live highlighting of additions and deletions, aligned side-by-side rows, a unified patch view and export — computed entirely in your browser. It is free, needs no account, and neither text ever leaves your device.
Last updated: October 16, 2026
A good online diff checker disappears into the task: paste, glance, done. This one opens straight into two editors with live results underneath — no comparison button to hunt for, no captcha, no file-size nag, no account. Under the hood it runs the same Myers algorithm family git uses, so the changes shown are exact rather than approximate, and the exported .patch is a standard unified diff you can apply with git apply.
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"); |
Online 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 check the difference between two texts online?
- 1
Paste the first text into the Original editor and the second into Changed — the diff renders immediately, no button needed.
- 2
Read the result: green rows are additions, red are deletions, and paired rows show lines that were edited in place with both versions aligned.
- 3
Flip to Unified for the classic +/- format, or to Words when the texts are prose and you want changed words highlighted inline.
- 4
Turn on Ignore whitespace to skip indentation-only churn, then copy the .patch or download it for records and reviews.
What an online diff should give you
Results before you finish pasting
The comparison recomputes on every edit with no submit step. Fix one line on either side and the highlight moves instantly — checking a one-character fix is a five-second task, not a five-click one.
Two views, one truth
Side-by-side aligns deletions with their replacements for review; unified compresses the same information into the compact +/- format you know from git. Both derive from the same computation, so they never disagree.
Standard .patch export, free
Copy or download a real unified diff with context lines — apply it with git apply, paste it into an issue tracker, or keep it as a receipt of what changed. Many online tools gate exports behind plans; this one does not gate anything.
Private even for sensitive text
Server-based diff sites receive both of your texts by design. This tool computes in your tab with no upload endpoint, so contracts, internal logs, unreleased code and personal data are never transmitted anywhere.
Mobile-friendly comparison
The editors stack on small screens and the diff scrolls horizontally where needed, so comparing two short texts on a phone works — the use case most tools quietly give up on.
Auto-save on both sides
Both texts persist locally between visits via your browser's storage. Come back later and the comparison is exactly where you left it — no session, no login, nothing in the cloud.
What makes a diff "exact"?
Exact means minimal: the tool computes the shortest sequence of edits that turns one text into the other, which is what the Myers algorithm optimizes. Approximate comparators instead heuristically match lines and can miss or misattribute changes — fine for a rough glance, misleading for review. Here, a highlighted deletion really is deleted, and every addition really is new text.
Exactness also makes the statistics meaningful. The added/removed counters at the top of the result are counts of real edit operations, so "3 added, 2 removed" is a factual summary of the change — useful when you need to describe an edit precisely in a commit message, a changelog or a standup update.
Choosing between line mode and word mode
Line mode is for structured text: source code, configs, logs, CSVs. It treats lines as the unit of change, which matches how version control and reviewers think, and produces the aligned rows and patch formats those workflows expect.
Word mode is for human text: paragraphs, documentation, emails, legal copy. Changing one word inside a 40-word sentence shows up as one highlighted word instead of a fully red-and-green sentence pair. If a line-mode diff looks like noise, switch to words; if a word-mode diff hides structure, switch to lines. The toggle is instant and both remain available.
Questions this tool answers
- online diff checker
- diff checker online free
- compare two texts online
- live diff tool
- unified diff generator online
Frequently asked questions
Is this online diff checker free?
Yes — every view and export is free with no account, no comparison limits and no watermarks. Because the computation happens in your browser, there is no server cost per comparison that would need to be recovered.
Do both texts get sent to a server?
No — the diff is computed locally in your tab and nothing is transmitted. This matters for exactly the texts people hesitate to paste online: contracts, internal documents, credentials-adjacent logs. The network tab stays empty.
Can it compare files I upload?
Paste is the input method — open both files in any text editor, copy each, and paste. This keeps the tool a single lightweight page with no upload pipeline, and works the same on phones where file pickers are clumsy anyway.
What does "ignore whitespace" change?
It treats lines that differ only in spacing (indentation, trailing spaces, double spaces) as identical. Use it after re-indenting a file — the diff then shows the real edits instead of every line lighting up red and green.
Is there a length limit?
No hard limit; very large comparisons (thousands of rows) skip the inline table to stay fast while the unified patch export continues to work at full size. For typical page- or file-sized texts, everything renders inline.
Does it work on a phone or tablet?
Yes — the layout stacks for small screens, controls are touch-sized, and the diff table scrolls. Comparing two pasted snippets on mobile is a supported use case here, not an accident.
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