Diff Checker
Compare two texts and highlight line-by-line changes.
About Diff Checker
A diff checker compares two pieces of text and highlights exactly what changed between them. This tool supports line-by-line comparison (best for code and structured text) and word-by-word comparison (best for prose). Added content is shown in green, removed content in red. All processing runs locally in your browser — nothing is sent to a server.
FAQ
- What diff modes are available?
- Line mode compares changes line by line. Word mode highlights individual word changes within lines.
- Is there a size limit?
- No hard limit, but very large texts may take a moment to process in the browser.
- Can I use this for code?
- Yes. Line mode is best for code since it shows exactly which lines changed.
- Is my text sent anywhere?
- No. All comparison runs locally in your browser.
ABOUT THIS TOOL
Paste two versions of any text - config files, code snippets, documents, or data exports - into the two input panes and see exactly which lines were added, removed, or changed, highlighted side by side. The comparison works line by line, so it catches whitespace differences, reordered lines, and partial edits within a line, which is easy to miss when eyeballing two files manually. This is the same basic idea behind version control diffs, just without needing git or any file history - useful any time you have two snapshots of text and need to know precisely what changed between them.
HOW TO USE
- Paste the original version of your text into the left pane.
- Paste the updated version into the right pane.
- Review the highlighted output showing additions, deletions, and changed lines.
- Scroll through longer texts to check for changes outside the immediately visible area.
- Copy specific changed sections if you need to document or report just the differences.
COMMON USE CASES
- A developer comparing two versions of a config file before and after a deployment to confirm only intended lines changed.
- A writer or editor comparing a draft against a revised version of an article to see exactly what changed.
- Someone comparing two exports of the same data, like a CSV or JSON dump taken at different times, to spot changed values.
- A developer reviewing a code snippet shared in a support ticket against their own working version to isolate the difference causing a bug.
- Someone comparing two drafts of a contract to check exactly which clauses were modified.
TIPS & COMMON MISTAKES
- Line-based diffing flags an entire line as changed even if only one character differs, so a single typo fix and a full rewrite can look similar in the highlighted output - read the actual highlighted text, not just which lines are marked.
- Differences in line endings, like Windows CRLF versus Unix LF, or trailing whitespace, can cause lines to show as changed even when the visible content looks identical - worth checking if a diff looks suspiciously large.
- Reordered but otherwise identical blocks of text typically show as a deletion in one place and an addition in another, rather than being recognized as a move, since basic line diffing doesn't track block relocation.
- For very large files, compare only the relevant section rather than pasting the entire file, since scanning hundreds of unrelated highlighted lines makes real changes harder to spot.
MORE QUESTIONS
- Does this diff tool understand code syntax, or is it purely text-based?
- It's purely text and line based - it doesn't parse code semantics, so a variable rename applied consistently across a file shows as many separate line changes rather than one logical rename.
- How does this compare to a git diff?
- The underlying concept is the same, comparing two texts line by line, but git diff also tracks file history and can detect renames or moves across commits - this tool is for comparing two arbitrary snippets of text you don't need version control for.
- Will trailing whitespace or invisible characters cause false differences?
- Yes, most line-based diffing is whitespace-sensitive by default, so trailing spaces, tabs versus spaces, or different line endings between the two versions can produce highlighted differences even when the text reads identically to the eye.
- Can it handle comparing very long documents, like an entire book chapter?
- It can, but readability degrades with very large inputs - for anything beyond a few thousand lines, comparing smaller sections at a time gives a clearer, easier-to-scan result.