Everything is marked as changed. Why?

Almost always line endings or indentation. One file uses Windows CRLF and the other Unix LF, or one has been reformatted. Turn on “Ignore whitespace” and the real differences appear.

Which comparison mode should I use?

Line for code and config, word for prose and documents, character when you are hunting a single-character difference such as a changed digit or a curly quote.

Are my documents uploaded anywhere?

No. The comparison runs in your browser, which is why this is a reasonable place to diff a contract, a credential file or an unreleased document.

Can it diff two files rather than pasted text?

Not yet — paste the contents for now. File-based diffing arrives with the file tools.

Text Diff

Compare two blocks of text line by line.

Everything runs inside your browser. Your files never leave your device.

Original

Changed

Result

The result appears here as you type.

Ask about Text Diff

Questions about what this tool does, which option to pick, or what it can and cannot handle.

This is the one part of the site that uses a server. The question you type here is sent to an AI provider to be answered — your files and whatever you put in the tool above are not, and the assistant cannot see them. Answers are generated and can be wrong; the tool itself is not guessing.

About the Text Diff

Two versions of something, and a question: what changed? A diff answers it far faster than reading both, and far more reliably — the eye skips over a changed digit or a swapped word without noticing.

This tool compares by line, by word or by character. Line mode is right for code, configuration and structured data, where a change belongs to a line. Word mode is right for prose, where a paragraph reflowing would otherwise mark every line as changed while only one word actually moved. Character mode is for the fine detail: a transposed pair of letters, a changed digit in an ID, a smart quote that replaced a straight one.

Two switches handle the noise. Ignoring case is useful when comparing exports from systems that disagree about capitalisation. Ignoring whitespace is useful when one file has been reindented or has different line endings — otherwise every single line reads as modified and the real change is buried.

Additions are shown in green, removals in red and struck through, and the counts above tell you the scale of the change before you read a line of it. Both texts stay in your browser, so comparing two versions of a contract, a config file or anything else confidential is safe.

How to use it

1Paste the original version into the first box.
2Paste the changed version into the second box.
3Choose how to compare: by line for code, by word for prose, by character for fine detail.
4Turn on “Ignore whitespace” if one version has been reindented or has different line endings.
5Read the coloured result — green is added, red struck through is removed.

Questions

Everything is marked as changed. Why?: Almost always line endings or indentation. One file uses Windows CRLF and the other Unix LF, or one has been reformatted. Turn on “Ignore whitespace” and the real differences appear.
Which comparison mode should I use?: Line for code and config, word for prose and documents, character when you are hunting a single-character difference such as a changed digit or a curly quote.
Are my documents uploaded anywhere?: No. The comparison runs in your browser, which is why this is a reasonable place to diff a contract, a credential file or an unreleased document.
Can it diff two files rather than pasted text?: Not yet — paste the contents for now. File-based diffing arrives with the file tools.