Question 1

What is a text diff checker?

Accepted Answer

A text diff checker compares two pieces of text and highlights every difference — added words, removed words, and unchanged content — making it easy to spot edits between versions. This tool uses the Longest Common Subsequence (LCS) algorithm to find the largest set of words that appear in both texts in the same order, then marks everything outside that sequence as either added or removed. The result is a word-level diff: each individual word is classified rather than each line or character.

Question 2

Is my text kept private?

Accepted Answer

Your text stays completely private because all comparison runs in your browser using JavaScript — nothing is ever sent to our servers. There is no account, no login, and no data stored anywhere outside your device. The moment you close or refresh the tab, your text is gone. This makes the tool safe for sensitive content: confidential contracts, personal writing, internal documents, or anything you would not want to upload to an external service.

Question 3

Can I compare text in any language?

Accepted Answer

Yes. The diff checker tokenizes text by splitting on whitespace, which works with any language that separates words with spaces — including English, Ukrainian, German, French, Spanish, Italian, Dutch, Portuguese, Swedish, Polish, and Korean. The tool handles Unicode correctly, so accented characters, Cyrillic script, and non-Latin alphabets all diff accurately. Note that languages without whitespace word boundaries, such as Chinese or Japanese, will treat runs of text as single tokens rather than individual words.

Question 4

What do the colors mean?

Accepted Answer

Green highlighted words were added in the revised text — they appear in the right panel but not in the original. Red highlighted words with a strikethrough were removed from the original — they appear in the left panel but not in the revised version. Gray words are unchanged and appear in both texts in the same position. The summary bar below the panels shows the exact count of added, removed, and unchanged words so you can gauge the scale of edits at a glance.

Question 5

Is this tool free?

Accepted Answer

Completely free with no registration required, no usage limits, and no premium tier. There are no file size caps and no restrictions on how often you use it. The tool is funded by non-intrusive display advertising and will remain free to use without an account.

Question 6

How large can the texts I compare be?

Accepted Answer

You can compare texts of any practical length — the tool imposes no hard size limit. Performance depends on your device, but most modern computers handle tens of thousands of words without noticeable lag. The LCS diff algorithm runs entirely in your browser, so processing time scales with text length and available CPU rather than any server constraint. For very large documents, results still appear within a few seconds on typical hardware.

Question 7

Can I use this tool to check for plagiarism?

Accepted Answer

The text diff checker is not a plagiarism detector, but it can be a useful first step when comparing two specific documents you already have. A plagiarism detector searches a database of known sources to flag copied content; this tool simply shows the differences between the two texts you paste in. If you suspect that a passage was copied and you have both the source and the suspected copy, pasting both here will reveal exactly which words match and which do not — word by word, with no ambiguity.

Question 8

Why do two texts that look identical show as different?

Accepted Answer

Almost always an invisible character. The usual culprits are a non-breaking space (U+00A0) pasted in from Word or a web page, a zero-width space (U+200B) picked up from a CMS, a smart quote (’) where the other side has a straight apostrophe ('), or Windows CRLF line endings meeting Unix LF. All four render identically on screen and are genuinely different bytes, so the diff is correct even though it looks wrong. Run both sides through Remove Spaces first — it straightens quotes and strips the invisible characters — and re-run the comparison. What remains after that is a real edit.

Question 9

What is the difference between word-level and line-level diff?

Accepted Answer

A line-level diff — what git diff and most code tools show you — marks an entire line as changed even if you only altered one word in it. That is the right behaviour for source code, where a line is a meaningful unit. For prose it is close to useless: reflow a paragraph and every line lights up, hiding the one word you actually changed. This tool diffs at word granularity, so a single swapped word is highlighted as exactly that and the surrounding sentence stays grey. Character-level diff goes finer still, but on prose it fragments words into noisy runs of coloured letters. Word level is the readable middle ground for anything written in sentences.

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How to Use the Text Diff Checker

Frequently Asked Questions

Further reading

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