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Diff Utilities

The pieces that sit around a comparison: unified patch output today, with merge, reports and list matching to follow.

About diff utilities

Not every comparison ends with reading it. Sometimes the diff is an intermediate step — the output has to become a file somebody can apply, a report somebody can attach to a ticket, or a reconciliation between two lists that were never files in the first place. This category collects the jobs that begin after the differences are found.

One utility is live. Patch Generator turns two texts into a standard unified diff with configurable context lines and editable file headers, ready for `git apply` or `patch -p1`. It also appears under text tools, because it is honestly both: the input is text, but the output is an artefact for another program rather than a view for a reader.

Three more are planned and none of them exists yet: a 3-Way Merge for reconciling two edits against a common ancestor, Diff to HTML for a self-contained report file, and List Compare for set operations across two pasted lists — what appears in both, what appears in only one. They are named on this page without links, deliberately.

Which utility do you actually need

Ask who is receiving the output. If the answer is a machine — a repository, a build step, a colleague who will run a command — you want Patch Generator, whose format is understood by git and by the standard patch utility, and whose context-line setting decides how much tolerance the result has for a target file that has drifted since. If the answer is a person, you rarely need this category at all: the export menu on Text Compare already produces a shareable link, a self-contained HTML report and a printable view directly from a comparison.

The gap worth naming is applying a patch, rather than making one. Nothing here does that yet, so a generated patch still has to go through git or the command line at the other end. That is the first thing on the list above, and it will be linked from this page when it works.

Patches are verbatim copies of your source

A unified diff is not a summary — it is a literal excerpt of the material it describes, changed lines and surrounding context reproduced exactly, which is why a patch of proprietary code is as sensitive as the code. Generation happens in your browser: the file headers you type, the context you choose and the output you copy or download all stay on your machine, and the download is written by the browser rather than fetched from anywhere. Open your browser's network tab while you use these tools — you'll see no request carries your content. Confirm it in DevTools.

Frequently asked questions

Why is Patch Generator listed in two categories?

Because it fits both descriptions and hiding it in one would cost somebody a search. Under text tools it is the fifth way to compare two texts; under utilities it is the thing that converts a comparison into a file another program can act on. The page is the same page, at one address, either way.

Can I apply a patch here as well as create one?

Not yet — Patch Applier is on the list above and is not built. For now, generate the patch here and apply it with git apply or the patch command on the machine that holds the target files, which is also where the operation belongs if you want its safety checks.

Will the patch apply cleanly to my repository?

It applies cleanly if the target matches what you pasted as the original side. Two things commonly break that: file headers that do not match the paths git expects, which you can edit before exporting, and a target that moved on since you copied it. More context lines make the result more tolerant of drift, at the cost of a larger file.

How do I share a comparison with a colleague today?

Three ways, none of which involve a server holding your data. A share link encodes both inputs in the URL fragment, which browsers never transmit. An HTML report exports as one self-contained file you can email. Or print to PDF for anyone who wants to annotate it by hand.