Kit — text diff

Text difference checker

Paste two versions and see which lines were added, removed or replaced — and, inside a replaced line, which words actually changed. It all runs in the page, so contract drafts and internal config files can be compared without leaving your machine.

Comparison rules
Layout

Paste text on both sides and the differences appear here.

This runs entirely in your browser. Nothing is uploaded.

Related tools

Word & character countJSON formatter & validatorBase64 encode & decodeImage resizeAll tools

How this one works

It looks inside the changed lines

A line-level diff reports a single fixed comma as "this whole line was replaced". Here every replaced line is compared again at word level, so only the part that moved is marked. The tokenizer keeps Latin words and numbers whole and splits everything else per character, which is what makes the same pass useful for Japanese, where words are not separated by spaces.

Your text stays on your machine

Contract revisions, internal configuration, unpublished drafts. Most online diff sites send what you paste to a server, so the comparison itself is the disclosure. Nothing is transmitted here.

Never colour alone

Additions carry a "+" and an underline, removals a "−" and a strike-through. The diff stays readable in greyscale, in print, and for anyone who cannot rely on the red/green distinction.

Reading the result

Line-level versus word-level — what is the difference?The line pass decides which lines were added, removed or replaced. The word pass looks inside a replaced line and marks the words that moved. This tool runs both and layers the word marks on top of the line verdict.
Why does every single line show as changed?Usually line endings. Windows writes CRLF and macOS/Linux writes LF, so two copies of identical text differ on every line as far as a byte comparison is concerned. This tool unifies line endings before comparing, so that cause is already handled. If everything still shows as changed, look for tabs swapped for spaces, or an encoding conversion that introduced full-width spaces.
What does the similarity percentage measure?Twice the number of unchanged lines, divided by the two line totals. Identical texts score 100%, texts with no line in common score 0%. It is a line-level figure, so small edits within a line barely move it.
How far does "ignore whitespace" go?It strips every space, full-width space and tab from a line before deciding whether the two lines match — useful when only the indentation was reworked. If you only want to forgive stray spaces at the end of a line, use "ignore trailing spaces" instead. Either way the options only affect matching; what you see on screen is the text exactly as you pasted it.

Questions

Is there a size limit?

5,000 lines per side. Above that the tool stops and says so rather than comparing the first few thousand lines — a partial result mistaken for the whole diff is the more expensive failure. For anything larger, git diff is the right tool.

Is my text stored?

No. Everything happens in the page and nothing is sent to a server. Close the tab and it is gone.

What is the unified diff for?

It is the standard "--- / +++ / @@" format that git and patch understand, with three lines of context around each change. Copy it into a review comment, or save it as a patch file.

Can I compare Word or PDF files directly?

No — this compares pasted text, so extract the text first. Formatting differences such as bold or colour are not part of the comparison.

Side-by-side or unified?

Side by side is better for checking which old line became which new one. Unified fits a narrow screen and reads top to bottom when you just want to walk through the changes. The underlying comparison is identical.