About
The Diff Checker compares two blocks of text or code and shows every difference in real time — no submit button required. Paste into the Original and Modified panels and differences appear immediately, colour-coded by type: lines added in green, removed in red, and modified lines in amber with character-level inline highlighting that pinpoints exactly which characters within a line changed. This character-level precision is what separates this tool from most online diff checkers, which only highlight entire lines. Two viewing modes are available. Split view places Original and Modified side-by-side with line numbers aligned, making it easy to read changes in context. Unified view mirrors the format used by git diff and patch files, with + and − prefixes and line numbers for both sides. The "Collapse unchanged" toggle hides unmodified lines (showing only three lines of context around each changed region) to bring the signal-to-noise ratio down to what matters — just like GitHub pull request diffs. Two normalisation options — Ignore Whitespace and Ignore Case — let you focus on semantic changes rather than formatting differences. The "Copy diff" button exports a standards-compliant unified diff string you can paste directly into a patch file or code review. File upload supports text, source code, JSON, YAML, Markdown, SQL, and more. All processing runs in your browser using a custom LCS algorithm — no data is sent anywhere.
How to use
- 1 Paste or type the original text into the left (Original) panel.
- 2 Paste or type the modified text into the right (Modified) panel — the diff appears immediately.
- 3 Use Split view to compare side-by-side, or Unified view for a git-style diff with + and − prefixes.
- 4 Enable "Collapse unchanged" to hide unmodified lines and focus only on what changed.
- 5 Toggle "Ignore whitespace" or "Ignore case" to suppress formatting-only or case-only differences.
- 6 Click "Copy diff" to copy a git-compatible unified diff string to your clipboard.
- 7 Click the Upload button on either panel to load a text or source-code file directly from your device.
- 8 Use the Swap button to reverse Original and Modified to see the inverse diff.
- What is character-level inline highlighting?
- Most diff tools only highlight entire lines as added or removed. This tool goes further: for lines that were modified (not wholesale added or removed), it runs a second diff on the individual characters within that line. The exact characters that changed are highlighted in a darker shade, making it easy to spot a renamed variable, a changed value, or a corrected typo without reading the entire line.
- What is the difference between Split and Unified views?
- Split view shows the Original text on the left and Modified text on the right, with line numbers aligned so matching lines appear at the same height. Unified view mirrors the format produced by "git diff" — both sides are shown in a single column with "−" prefixes on removed lines and "+" prefixes on added lines. Unified view is more compact; split view is easier to read when many lines change on both sides simultaneously.
- What does Collapse Unchanged do?
- When enabled, lines that are identical in both versions are hidden, showing only three lines of context around each changed region (just like GitHub or GitLab pull request views). This makes large files much easier to review by removing noise. Click the "X unchanged lines hidden" bar to expand any collapsed section.
- Is there a file size limit?
- File uploads are limited to 2 MB per side. There is no hard limit on pasted text, but the diff algorithm is O(nm) in the worst case so very large files (tens of thousands of lines) may take a moment to compute. Prefix/suffix optimisation means files that share most of their content compute near-instantly regardless of total size.
- Is my content sent to a server?
- No. The entire diff — LCS computation, character-level analysis, unified diff generation — runs in your browser using JavaScript. Nothing is ever transmitted to CodeLint.Dev servers or any third party. This makes it safe to paste source code, configuration files, private documents, or any sensitive content.
- What file types can I upload?
- Any UTF-8 text file works: .txt, .js, .ts, .jsx, .tsx, .json, .yaml, .yml, .md, .css, .html, .xml, .py, .java, .go, .rs, .rb, .php, .sh, .sql, .csv, and more. Binary files are not supported.