Free Online Diff Checker — Compare Text & Code Side-by-Side
Paste two blocks of text or code into UtilHub's Diff Checker and see every difference highlighted instantly. Added lines, removed lines, and modified words are color-coded so you can spot changes at a glance. The side-by-side view is what you want when a config file worked yesterday and does not today, or when a document comes back from review with no track-changes turned on. No account needed, nothing uploaded anywhere.
How to use Diff Checker
- Paste original text — Enter or paste the original text in the left panel. This can be code, prose, JSON, CSV — any plain text content.
- Paste modified text — Enter or paste the changed version in the right panel. The tool instantly computes the difference using a line-by-line comparison algorithm.
- Toggle view mode — Switch between side-by-side and inline diff view. Side-by-side places original and modified text in parallel columns — ideal for code review. Inline merges both into a single column with color-coded additions and deletions — better for reviewing prose and documentation.
- Review the differences — Added lines highlight in green, removed lines in red, and unchanged context stays neutral. Toggle "Ignore whitespace" to filter out noise from spacing changes and focus on meaningful edits.
Features
- Side-by-side view — Both versions sit in one aligned table, so every changed line lines up with its replacement and they scroll together.
- Inline diff mode — Switch to a unified view that shows changes in a single column with additions and deletions marked inline.
- Word-level highlighting — Not just line-level diffs — changed words within a line are highlighted individually so you can pinpoint exact modifications.
- Open files or paste — Load each side from a file on your computer, or paste text; files are read locally.
- Ignore whitespace option — Toggle whitespace sensitivity to focus on meaningful content changes and ignore formatting differences.
Frequently Asked Questions
Can I compare code snippets with this diff checker?
Yes. The diff checker works with any plain text, including source code in any programming language. It highlights differences at both the line and word level, making it ideal for comparing two versions of a function, config file, SQL query, or any other code snippet.
Does the diff checker ignore whitespace differences?
You can toggle whitespace sensitivity on and off. When whitespace is ignored, differences in indentation, trailing spaces, and blank lines are excluded from the comparison. This is useful when comparing code that may have been reformatted but is functionally identical.
What is the difference between inline and side-by-side diff?
Side-by-side diff shows original and modified text in two separate columns, letting you scan left-to-right like a code review tool (similar to GitHub's "Split" view). Inline diff merges everything into one column where deletions show as red strikethrough and additions as green highlighted text — similar to "Track Changes" in Microsoft Word. Side-by-side is best for structured code; inline is better for paragraphs and documentation.
Can the diff checker handle large files?
Yes. Since processing happens entirely in your browser, there are no upload limits or server restrictions. The diff algorithm is optimized for files up to 50,000+ lines. For very large files, the tool automatically collapses unchanged sections to highlight only the changed regions, keeping the output readable.