Diff Checker — Free Online Text & Code Comparison Tool

A diff checker (also called a text compare tool or diff tool) compares two blocks of text or code and highlights the differences between them — which lines were added, removed, changed, or moved. Essential for code reviews, document edits, config comparisons, and content editing.

Yes, 100% free with no limits. Unlike Diffchecker.com, which charges $9/month for syntax highlighting and file uploads, this tool gives you everything — character and word-level diffs, split and unified views, moved-line detection, a merge builder, file uploads — all free, no signup, no paywall, no ads.

Yes. This diff checker runs entirely in your browser using JavaScript. No text is ever sent to a server, and comparison history is saved only in your own browser's local storage. You can verify this in your browser's network tab — zero outbound requests with your content.

Any plain-text format: source code (JavaScript, Python, Java, Go, and so on), config files (YAML, JSON, XML, .env), Markdown and prose, CSV, SQL, log files — anything that opens as text. Binary files (images, PDFs, compiled binaries) aren't supported since there's no meaningful line-by-line comparison for them.

Split view shows the original on the left and the modified text on the right, aligned line by line — ideal for side-by-side comparison. Unified view shows both versions in a single column with + and - prefixes, similar to git diff output — great for reviewing changes sequentially or pasting into a PR.

When a line is changed rather than purely added or removed, this tool can highlight exactly what differs inside that line. Character granularity marks the precise characters that changed (great for code, where red → blue should highlight just those letters). Word granularity marks whole words instead, which reads more naturally for prose and long sentences. Off just shows the whole line as changed, with no inline highlighting.

It's the share of lines that are identical between the two texts (unchanged lines ÷ total lines). 100% means the texts are identical; a low percentage means most of the content differs. It's a quick way to gauge how substantial an edit was before reading the full diff.

It hides unchanged lines that are far from any difference, showing only a few lines of context around each change — the same idea as git diff's default output. Useful for large files where you only want to see what actually changed, not the entire unchanged body of the document.

Yes. Use the search bar above the diff output to find text anywhere in the rendered comparison — matches are highlighted and the ▲/▼ buttons jump between them. Handy for jumping straight to a specific function name or line in a long diff.

It ignores differences in spaces, tabs, and indentation entirely when comparing lines. Useful when comparing code that's been reformatted or re-indented by a linter, where only the actual content matters, not the whitespace around it.

It compares text case-insensitively, so Hello and hello are treated as identical. Useful for comparing content where capitalization is inconsistent but not meaningful to what you're checking.

Trim trailing spaces only removes whitespace at the end of each line before comparing — useful for editors that silently strip trailing spaces on save. Ignore whitespace is broader: it collapses all whitespace differences anywhere in the line, including indentation and multiple spaces between words.

When a line (or block of lines) was deleted from one place and an identical line reappears elsewhere, this tool marks both as moved (shown in purple) instead of a plain removal plus addition, with a small “moved to/from line N” hint. This avoids the common diff-tool confusion where reordering a list looks like every item was rewritten.

Usually one of two things: a change in indentation style (tabs vs spaces), or every line being re-wrapped by a formatter. (Mixed line endings aren't a concern here — browsers normalize CRLF/LF automatically, so this tool never sees them as a difference in the first place.) The Suggestions panel flags whitespace, case, and indentation mismatches automatically when detected, with a one-click option to enable the relevant setting (like Ignore whitespace) and re-run the comparison.

After running a comparison, this tool analyzes the result and surfaces plain-language observations you might otherwise miss: whitespace-only or case-only changes, mismatched line endings, an indentation style mismatch, moved blocks, or an unusually high proportion of changed lines. Where relevant, a suggestion includes a one-click button to apply the fix and re-diff.

Click Merge builder after running a diff to build a combined result line by line. Every difference gets A / B buttons so you can pick the original or modified version for that specific line (defaulting to the modified version), while unchanged lines are kept automatically. The merged text updates live and can be copied or downloaded — useful for resolving a diff by hand without a full merge tool.

Yes. Open the History panel to see your recent comparisons, saved only in your browser's local storage. Click an entry to restore both texts and re-run that comparison, or clear the list anytime.

Yes. Click Load file on either side to select a file, or use Paste to pull directly from your clipboard. Any plain-text file works — code, config, log, CSV, JSON, and so on — and it's read entirely in your browser, never uploaded.

Click Copy diff to copy the comparison to your clipboard in standard unified-diff format, ready to paste into Slack, email, or a pull request description. Download .diff saves it as a file instead.

Yes. Use ?a=...&b=... with URL-encoded text for each side, and the page loads with both texts already compared — useful for deep-linking a specific comparison or letting a script or AI agent trigger a diff directly.

Ctrl+Enter (or Cmd+Enter on Mac) runs the diff from anywhere on the page. Tab inside either text area inserts an actual tab character instead of moving focus, which matters when editing code by hand.

Diffchecker.com paywalls syntax highlighting, file uploads, and diff history behind a $9/month subscription. Meld is a desktop app that needs installing. This tool provides all of those, plus word-level diffs, moved-line detection, a merge builder, and smart suggestions, free in your browser — no install, no account, no limits.

Yes, for typical source files and documents (thousands of lines). The diff algorithm's cost grows with the number of differing lines, so a very large file with very few changes stays fast, while two huge files that are almost entirely different will take noticeably longer. Turning on Context only also makes large diffs much faster to read.

Yes, once the page has loaded. Everything — diffing, highlighting, suggestions, merging — runs in plain JavaScript with no runtime calls to any server, so it keeps working on a plane, on a locked-down network, or with your connection off.