🔍 Diff Checker
Compare two texts and instantly see every addition, deletion and change highlighted — word by word or line by line. Free, private, no signup.
Last updated: June 2026
About This Diff Checker
This diff checker is a free online tool that compares two versions of any text and highlights every difference — additions appear in green and deletions in red strikethrough, giving you an instant visual overview of what changed between any two documents, code snippets, or blocks of copy. Paste the original on the left, the modified version on the right, and click Compare for a complete breakdown.
The diff checker runs in two modes. Word mode analyses text token by token using a Longest Common Subsequence algorithm — ideal for documents, emails, blog posts, and any prose where individual word changes matter most. Line mode treats each newline as a single unit, making it better suited for code, configuration files, and structured data where entire rows are added or removed at once.
Two extra features speed up your workflow. Side by Side view splits the result into two synchronised panels — original on the left with removals highlighted, modified on the right with additions — so you can read through both at the same pace. Download Diff exports the full comparison as a plain-text file annotated with + and − markers, useful for sharing with colleagues or keeping a revision record. Everything runs entirely in your browser — no text is uploaded or stored.
How to Use This Diff Checker
How the Diff Checker Works
Getting started with this diff checker takes no setup at all — paste two texts and click Compare.
Step 1 — Paste your original text into the left panel. This is the starting version before any edits — a first draft, an older config file, or the original copy of an email.
Step 2 — Paste your modified text into the right panel. This is the updated version you want to compare against to find changes — the revised draft, updated config, or edited document.
Step 3 — Choose your diff mode. Select Word to compare text word by word, which shows precisely which words were added or removed within a sentence. Select Line to compare row by row — better for code, logs, and content where each line is a meaningful standalone unit.
Step 4 — Click Compare. The diff checker highlights every difference instantly. Green marks show additions; red strikethrough marks show deletions. The statistics bar shows exactly how many words or lines were added, removed, or unchanged across the full comparison.
Step 5 — View or export. Switch to Side by Side to read both versions in parallel with synchronised scrolling. Click Download Diff to save a plain-text export annotated with + and − markers — ideal for sharing results or archiving a revision record. No signup required — free forever.
Who Is This Diff Checker For
This diff checker is built for anyone who needs to compare text, find changes between two document versions, or spot differences in code or data quickly and accurately.
- Developers comparing code snippets, configuration files, JSON payloads, or API responses before and after a change — switch to Line mode for code.
- Writers and editors tracking exactly what changed between draft versions of an article, report, or email to confirm all revisions were applied correctly.
- Students comparing essay revisions to verify that all tutor feedback was addressed before the final submission deadline.
- QA testers checking text output differences between software builds, translated strings, or auto-generated content across environments.
- Legal and compliance teams reviewing contract or policy revisions to identify every clause that was added, changed, or removed between versions.
Explore all our free Text Tools for more ways to work with text online.
Frequently Asked Questions
What is a diff checker?
A diff checker is a tool that compares two versions of a text and highlights every difference between them. Additions appear in green and deletions in red strikethrough. This diff checker runs entirely in your browser — no text is sent to any server.
How does the diff checker compare text?
The diff checker uses a Longest Common Subsequence (LCS) algorithm. In Word mode, both texts are split into individual word tokens and the algorithm finds the longest matching sequence. In Line mode, each newline is treated as a single unit. Words or lines present only in the modified text are marked as additions; those only in the original are marked as deletions.
What is the difference between Word and Line diff mode?
Word mode compares text token by token and is ideal for documents, emails, and prose where individual word changes matter most. Line mode treats each newline as a single unit and is better suited for code, configuration files, and structured content where entire lines are inserted or removed. For everyday text comparison, Word mode gives more readable results.
Can I use this diff checker for code comparison?
Yes. This diff checker works with any plain text including source code in any language — JavaScript, Python, HTML, CSS, SQL, JSON, YAML and more. Switch to Line mode for code, as each line is typically a meaningful unit. The result shows exactly which lines were added, removed, or unchanged.
Is this diff checker free to use?
Yes, this diff checker is completely free with no signup required. There are no size limits and no hidden costs. All comparison happens locally in your browser — your text is never uploaded or stored anywhere. Free forever, no hidden limits.