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Text Diff

Find line-by-line differences between two texts.

Original (A)

Modified (B)

0 B uploaded — nothing you enter has been sent anywhere?

Nothing you enter and no file you choose is sent anywhere — everything runs inside this page, and no request carries your content to a server.

Other tools send what you type to a server and process it there. Even when they promise to erase it afterwards, your text sits on someone else’s machine in the meantime. Here there is no sending step at all. The more sensitive the content — passwords, contract wording, private notes — the more that difference matters. See how to verify it →

Find exactly which lines changed between two versions of a text

When two drafts look almost the same, checking them by eye is how a changed clause slips through. This tool lines up an original and an edited version line by line and colors every line that was removed or added. The comparison runs inside your browser, so what you paste stays on your device.

A closer look

The comparison looks for the longest run of lines that appear in both texts in the same order, known as the longest common subsequence. Those shared lines are shown in grey. Lines found only in the original get a “-” and turn red; lines found only in the edited version get a “+” and turn green. The result is a single column, and where several lines changed in one spot, the removed lines are grouped first and the added lines follow. The status line sums it up, for example “2 line(s) added, 1 removed”.

Two lines only count as the same if they match character for character. A trailing space, a tab instead of spaces, or curly quotes that a word processor swapped in will all register as a change. If you edit one word in a line, the whole line appears once as “-” and once as “+”; the tool does not highlight the individual characters inside it. Windows and Mac line endings, on the other hand, do not show up as differences, because the browser’s text box normalizes line breaks when you paste. The two texts can have up to 6,000 lines combined.

How to use it

Paste the earlier version into Original (A) on the left and the edited version into Modified (B) on the right. If you swap them, additions and removals are reversed.
Press Compare. The result appears below the boxes and the status line shows how many lines were added and removed.
Red “-” lines exist only in the original and green “+” lines exist only in the edit. Grey lines are identical on both sides, so you can skim past them.
If you fix something in either box, press Compare again and the result is recalculated from scratch.

When it helps

Reviewing a returned contractCompare the copy the other party sent back with your original to make sure no amount, date or term changed without being mentioned.

Config files across serversPaste the config from a working server and from a broken one to spot the one or two values that differ, even when the files contain passwords.

Membership list changesSort last month’s and this month’s lists the same way; new members show up as “+” and people who left as “-”.

Checking an editor’s passPut your manuscript and the proofread version side by side and read only the sentences that were touched.

Common snags

I changed one word and the whole paragraph is flagged.The unit of comparison is the line. If a paragraph is one long line with no breaks, any edit flags all of it. Put each sentence on its own line in both texts and the result narrows to the sentences that actually changed.

Lines that look identical are marked as changed.There is an invisible difference: trailing spaces, tabs versus spaces, straight versus curly quotes, or a non-breaking space. There is no ignore-whitespace option, so clean up trailing spaces in an editor and compare again. An extra blank line at the end of one text also shows up as one changed line.

I only moved a paragraph, but it shows as deleted and added.Moves are not detected as such. The block appears as “-” where it used to be and “+” where it is now; if you see the same text in red in one place and in green in another, read it as a move.

It says “Too many lines (6,000 lines combined max)”.Both boxes together are over the limit. Split a long document by chapter or section and compare the parts one at a time.

Tip For lists where order does not matter, such as names or IDs, sort both versions the same way before pasting so that only the real additions and removals remain.

Notes

Can I paste contracts or code?

Yes. The comparison runs entirely inside your browser and nothing is transmitted.