1. [Home](https://www.toolcomb.com/) 2. [Text Tools](https://www.toolcomb.com/text-tools) 3. Diff Checker # Diff Checker Online Free - Text Compare & Code Diff Tool Free online diff checker and text compare tool. Paste Original and Modified text for a line-based code diff with added, removed, and unchanged highlighting - plus optional unified diff copy. Browser-only. ### Original _Paste the original / baseline text…_ ### Modified _Paste the modified / new text…_ Copy unified diff Clear +0 · −0 · 0 unchanged ### Line diff Paste text on both sides to see added, removed, and unchanged lines. ## What is an online diff checker? An online diff checker (also called a text compare tool or code diff viewer) shows the difference between two versions of a document. You paste an Original baseline and a Modified revision; the tool marks lines that were removed, lines that were added, and lines that stayed the same. Writers use it for editorial passes, developers for snippet review outside Git, and support teams for comparing config exports from two environments. Line-based comparison is the workhorse format of software history. Git, patch files, and most code review UIs think in lines because humans read source and prose that way. This page compares the two inputs line by line and classifies changes as removals, additions, or unchanged context. The result is a clear visual diff you can skim in the browser. Optional unified diff export mirrors the classic patch style with leading spaces for context, minus for removals, and plus for additions. That clipboard format travels well into tickets, Slack threads, and email when you cannot open a repository but still need a portable summary of what changed between two pastes. Privacy matters when the texts are contracts, customer data samples, or unreleased code. Many “free” compare sites upload both sides to a server. ToolComb’s diff checker runs locally in your tab and discards the comparison when you clear or leave. Prefer not to paste secrets at all; when you must compare configs, local processing is the safer default. This is not a full merge tool. It will not resolve conflicts, understand renames, or ignore minified one-line bundles gracefully. It will, however, answer the everyday question “what changed between these two pastes?” quickly enough to keep you moving - which is exactly what a browser text compare tool should do. Teams often keep two windows open: a CMS or email client on one side and this diff checker on the other. Paste the published version as Original and the draft as Modified, then walk the green and red lines in a stand-up. Because the comparison is deterministic over exact line strings, everyone sees the same highlights - unlike eyeballing two scrolls and arguing about whether a paragraph moved or was rewritten. When the review ends, copy the unified diff into the ticket so the decision trail stays attached to the work item. For source snippets, pair the diff with your formatter: run Prettier or an equivalent on both sides first so indentation noise does not drown semantic edits. For prose, consider collapsing soft-wrapped lines into true paragraph breaks before comparing, because a single logical sentence split differently across two exports will look like a full-line change even when the words are identical. ## How to compare text with this diff checker A full compare takes under a minute. Use these steps for prose, configs, or short source files. 1. **Paste the Original side** Put the older or authoritative version in the left (Original) textarea. Keep the content as plain text; rich formatting from Word is stripped to characters when you paste, which is usually what you want for a code diff or plain-text compare. 2. **Paste the Modified side** Put the newer version in the right (Modified) textarea. Try to preserve similar wrapping so unchanged paragraphs stay aligned. If one side was auto-formatted, consider formatting both with the same rules first. 3. **Scan added, removed, and unchanged lines** Green marks additions present only in Modified. Red marks removals present only in Original. Neutral rows are shared lines. Scroll the result panel to review long documents without losing the color legend. 4. **Copy a unified diff when you need a patch-style summary** Primary Copy unified diff writes a --- / +++ header plus -/+/space lines to the clipboard. Paste into a ticket or chat so reviewers can read the change set without opening both full texts again. 5. **Iterate or clear** Edit either textarea to refine the comparison live. Outline Clear empties both sides and the result so the next pair of documents does not mix with leftover content. 6. **Know when to switch to Git** If the files live in a repository with history, prefer git diff or your IDE. Use this online diff checker for email drafts, CMS fields, support snippets, and one-off pastes that never were commits. ## Before / after: catching a silent config change ### Before Two Kubernetes ConfigMap YAML dumps look identical at a glance. A timeout value moved from 30s to 5s on one line, and a comment was deleted. The engineer needs to confirm the delta before approving a rollback, but the files are not in the same Git history on their laptop. ### After They paste yesterday’s dump into Original and today’s into Modified. The diff checker highlights the removed 30s line in red and the added 5s line in green, leaves the rest unchanged, and they copy a unified diff into the incident channel as evidence. The same pattern works for Terms of Service revisions, README rewrites, and CSV header renames - anything where “show me the lines that changed” is the entire job. ## Practical uses for a text compare / code diff tool ### 1. Editorial revisions of articles and policies Editors paste draft A and draft B to see which paragraphs moved or vanished before publishing legal or help-center updates. ### 2. Config and infrastructure snippets Compare nginx blocks, Terraform fragments, or .env samples from staging versus production without cloning both repos. ### 3. Code review outside a pull request Mentors paste a student’s function and a suggested rewrite. The code diff tool focuses discussion on changed lines instead of re-reading the whole file. ### 4. Localization string files L10n teams compare English and translated JSON or properties files to spot missing keys that appear as removals or additions. ### 5. Support ticket reproductions Agents compare customer-provided logs or settings exports against a known-good template to find the divergent line quickly. ### 6. Documentation sync Technical writers verify that a changelog section matches the README feature list by comparing the two Markdown blocks. ### 7. CSV and data dictionary checks Analysts paste two header rows or schema dumps to ensure column renames are intentional before a pipeline runs. ### 8. Email and CRM template QA Marketers compare last week’s campaign HTML (as text) with this week’s to confirm tracking parameters and CTAs. ### 9. Exam or assignment integrity spot-checks Instructors compare a submitted answer against a sample solution at line granularity for structure - not as a plagiarism product, but as a teaching aid. ### 10. Crontab and script edits Pair with the cron expression generator: paste old and new crontab files here to audit schedule changes before deploy. ### 11. API contract and OpenAPI snippets Backend and mobile teams paste two YAML or JSON fragments from OpenAPI specs to spot breaking path or field renames before a release train locks. ### 12. Incident timeline narratives After an outage, compare the first status draft with the final postmortem summary to ensure corrections did not silently drop key facts when the document was rewritten under time pressure. ## Diff checker options compared Many tools can show differences. Choose based on privacy, algorithm needs, and whether you already have Git. | Option | Privacy | Granularity | Best for | | --- | --- | --- | --- | | ToolComb browser diff checker | Local paste only | Line comparison + unified copy | Quick private text compare | | git diff / IDE | Local repo | Lines, sometimes words; history aware | Versioned projects | | Desktop merge tools | Local files | Rich 2- and 3-way merges | Conflict resolution | | Upload-based online diff sites | Texts sent to a server | Varies | Non-sensitive casual pastes | Stay in Git when history matters. Use this page when the two versions exist only as clipboard contents and you need an immediate, private line diff. For three-way merges with a common ancestor, reach for a desktop merge tool; for two pastes and a yes/no on what changed, this online text compare is enough. ## Limits and tips - Line-based only - character edits inside a long line show as a full-line remove plus add. - Huge files may lag on low-power devices. - Minified single-line assets produce unhelpful giant line replacements. - Whitespace and indentation differences count as real changes. - No binary file support (images, PDFs); paste text only. - Unified export is a simplified patch (not a full git apply-ready hunk with @@ headers). - Does not ignore blank-line-only noise unless you remove those lines first. - Not a legal redline product with tracked changes semantics from Word. ## Privacy: comparison stays in your browser Original and Modified text never leave your device for comparison. The comparison runs in memory inside the tab. That suits unpublished manuscripts, customer configs, and internal runbooks. Still avoid pasting passwords or private keys - clearing the UI does not erase your clipboard if you copied a unified diff containing secrets. No account means no cloud history of comparisons. Close the tab when finished on a shared computer. ## Frequently Asked Questions ### What is a diff checker online? A diff checker compares two texts and highlights what changed. This tool is a line-based text compare and code diff viewer: it marks lines added in the modified version, lines removed from the original, and lines that stayed the same. ### How does this text diff checker compare text? It compares lines locally in your browser and shows lines that were added, removed, or left unchanged. No upload or account is required. ### What is a unified diff? Unified diff is a common patch format with - lines for removals and + lines for additions, plus context lines. Copying unified diff gives you a portable summary for Git-like discussions even when you are not in a repository. ### Can I compare code as well as prose? Yes. The code diff tool treats each line as a unit, which works well for source files, JSON, YAML, CSV, and Markdown. Extremely long single-line minified files will show as large replacements when the whole line changes. ### Does it highlight character-level changes inside a line? No. This version is line-based for clarity and performance. If one character changes inside a long line, the whole line appears as removed and added. Split long lines or use a dedicated IDE for word-level diffs when needed. ### Is my text uploaded? No. Comparison runs entirely in your browser. Draft contracts, private keys in configs you should not paste elsewhere, and unpublished code stay on your device - still avoid pasting secrets into any tool when possible. ### How large can the texts be? Very large files (thousands of differing lines) may feel slow on phones. For multi-megabyte logs, sample sections or use Git locally. Typical essays, configs, and source files are fine. ### Does whitespace matter? Yes. Trailing spaces and indentation differences make lines unequal. Normalize formatting first if you only care about semantic changes. ### Can I use this instead of git diff? For quick paste comparisons outside a repo - emails, CMS drafts, snippets from tickets - yes. For versioned projects, git diff remains better because it understands history, renames, and binary files. ### Is the diff checker free? Yes. Unlimited local compares, no account, and no watermark on copied unified diffs. ## Related text tools - [Word Counter](https://www.toolcomb.com/word-counter) - Measure length before and after you trim a draft. - [Case Converter](https://www.toolcomb.com/case-converter) - Normalize casing that might create noisy diffs. - [HTML ↔ Markdown Converter](https://www.toolcomb.com/html-markdown-converter) - Normalize markup, then compare the plain result. - [Cron Expression Generator](https://www.toolcomb.com/cron-expression-generator) - Build schedules, then diff crontab files here. ## Related Tools Discover more free tools that might help with your next task. [Case Converter Convert text between upper, lower, title cases and more Use Tool](https://www.toolcomb.com/case-converter) [HTML ↔ Markdown Converter Convert between HTML and Markdown Use Tool](https://www.toolcomb.com/html-markdown-converter) [Lorem Ipsum Generator Generate placeholder text for design and content Use Tool](https://www.toolcomb.com/lorem-ipsum-generator) [Regex Testing Test and validate regular expressions Use Tool](https://www.toolcomb.com/regex-testing) [Word Counter Count words, characters, and reading time instantly Use Tool](https://www.toolcomb.com/word-counter) [Cron Expression Generator Build and explain crontab schedules in plain English Use Tool](https://www.toolcomb.com/cron-expression-generator) ### Related guides Read the how-to, then come back to this tool when you are ready to run it locally. - [Diff Checker vs Unified Patch - Which Output Do You Need? Side-by-side diffs for humans, unified patch text for git apply and review bots - when to use each ToolComb tool and how to avoid line-ending surprises.](https://www.toolcomb.com/blog/diff-checker-vs-unified-patch) - [Best Free Developer Text Tools in the Browser Word counts, diffs, cron, Markdown, slugs, regex replace, SQL format, and JS minify - when to open each ToolComb text tool locally without uploading source.](https://www.toolcomb.com/blog/best-free-developer-text-tools) [View All Tools](https://www.toolcomb.com/tools)