# Diff checker: run it free, or from your agent

Compares two texts line by line, side by side or inline, marks changed words and counts added and removed lines.

## Prompt

Use looot to see what changed on a web page since my last check. 1. Set up https://looot.ai/skill.md. 2. Search the catalog for an endpoint that returns a page as markdown and check its price before you call. 3. Fetch [URL] and save the markdown. 4. Compare it with the copy I paste here: [old text]. 5. List the added and removed lines and sum up the change in two sentences.

## What it needs

Two blocks of text

## What comes back

- side by side diff
- inline diff
- added and removed line counts
- unified diff text

## Endpoints and providers

None. The tool on the web page runs in the browser and calls no endpoint.

## What it costs

Nothing. The tool on the web page runs in the visitor's browser: no account, no API call and no limit per hour. The prompt above runs the same job from your own looot account with current data, billed per call.

## Review a change

Compare two versions of a config, a contract or a prompt before you ship it.

## Check agent edits

See exactly what an agent rewrote in a file or a draft.

## Compare exports

Paste two CSV or JSON exports and find the rows that moved.

## Page changes

Diff two copies of a web page's text to see what the site changed.

## How do I compare two texts?

Paste the first version on the left and the second on the right. The result updates as you type. Swap sides flips which one counts as the original.

## Which diff algorithm does it use?

The Myers algorithm, the default in git diff. It finds the smallest set of added and removed lines that turns one text into the other. Changed words inside a line are found the same way at word level.

## Can it ignore whitespace and case?

Yes. Ignore whitespace treats runs of spaces and tabs as one and skips spaces at line ends. Ignore case compares letters without case. Windows and Unix line endings always compare equal.

## How big can the texts be?

Up to 500,000 characters per side. Two long texts with a few changes compare quickly. Two long texts that share almost nothing can hit the edit limit, and the page then asks you to compare a smaller part.

## Can I export the result?

Copy diff and the .diff download give the comparison as unified diff lines, with - for removed and + for added. The output has no hunk headers, so git apply will not take it as a patch.

## Does it compare files or folders?

It compares text you paste. Open each file, copy its text into one side. For whole folders use git diff or diff -r on your machine.

## Is my text uploaded?

No. The comparison runs in your browser. Nothing you paste is sent or stored.

## Related tools

- /free-tools/json-formatter
- /free-tools/regex-tester
- /free-tools/markdown-to-html

## Last reviewed

2026-10-14.