llms.txt is a proposed plain-text file at your domain root that tells AI crawlers how to use your content — your description, key pages, licensing, and crawler policies. As you edit it over time, a diff shows exactly what changed between versions so you can confirm intended updates landed and catch accidental deletions of important pages or policy lines.

Paste the old version on one side and the new version on the other. The tool compares them line by line and labels each line as unchanged, added, or removed, then summarizes the totals. It runs entirely in your browser using a lightweight line-comparison algorithm — no file is uploaded and no AI API is involved.

It works at the line level, so an edited line appears as one removed line plus one added line. The summary counts added and removed separately, which makes even small wording changes easy to spot. For a file like llms.txt, where each line is a discrete directive or page entry, line-level diffing is precise and easy to read.

By default it compares lines exactly, including case and surrounding whitespace, because in llms.txt those details can matter (paths, URLs, and directives are case-sensitive). Trailing spaces or a changed slash will show as a difference, which is intentional so you do not miss subtle but meaningful edits.

Yes. The diff is generic line-based comparison, so it works on robots.txt, sitemaps in text form, configuration snippets, or any plain text. It is tuned and labeled for llms.txt workflows, but nothing stops you from pasting other text files to compare versions.

Completely. All processing happens locally in your browser via client-side JavaScript. The contents you paste are never transmitted to our servers or any third party, and nothing is stored. You can use it on internal or unpublished files without privacy concerns.

Once you have confirmed your changes with the diff, run the new file through our llms.txt Validator to check it against the spec — required sections, well-formed links, and crawler-policy syntax. Diff confirms what changed; the validator confirms the result is still correct.