什么时候在线对比工具比 git diff 更合适，什么时候不是

把浏览器对比和 Git 分清楚：片段、审阅、临时文件，对上历史记录、分支和合并。

2026年11月15日 · 8 min

本文正文目前为英文。

git diff is the right tool whenever the text you are comparing already lives in a repository. An online diff tool is the right tool when it does not. Mixing those two jobs up is what makes people say a browser diff is "not serious", or, the other way around, waste twenty minutes initializing a repo just to look at two pasted files.

This article draws a clean line between the two, so you can pick quickly and avoid treating a website as a substitute for version control.

What git diff is actually for

Git compares snapshots that are already connected to history. A typical git diff answers questions like: what did I change since the last commit, what is on this branch that is not on main, or what will this merge bring in. It can walk renames, restrict the comparison to a path, and feed a patch into git apply. The result belongs to a project, not to a one-off paste.

That is also why Git is a poor first step for throwaway text. If someone sends you two versions of a JSON payload or a paragraph of copy, creating a repository, writing files, and running git diff --no-index is possible, but it is ceremony around a five-second question.

What an online diff tool is actually for

A browser diff answers a narrower question: how do these two texts differ, right now. There is no branch, no author, and no commit. That is a feature when:

The files are not in Git yet — email attachments, log excerpts, CMS drafts, config exports.
The person you are helping does not have the repo, or should not be asked to clone it.
You want a word-level or character-level view that git diff does not give you by default.
You are comparing formats with a little structure, such as XML or JSON, and want formatting normalized first. See the guide on comparing XML online.

DiffCheck keeps that comparison in the browser. It is a viewer, not a history store. If you need a unified patch from two texts, the Diff Patch Generator can produce one; you still apply and commit that patch in Git if the change belongs in a project.

A short decision rule

Use Git if the change should be recorded, reviewed as a pull request, reverted later, or attributed to an author.
Use an online diff if you only need to understand two versions you already have in front of you, especially if they never belonged to a repo.
Use both when you first inspect a pasted change in the browser, then re-apply the same edit in a branch so tests and review can run.

If you are comparing source code you intend to merge, start in Git. If you searched for an online tool because the text arrived outside a repo, start with Code Diff or the text comparison on the homepage, then move anything you decide to keep back into version control.

Limits you should not ignore

Online diffs do not track moves across commits, do not run hooks, and do not resolve merge conflicts. They also cannot tell you whether a deleted function is still referenced elsewhere in the project. Git, plus your editor and tests, still owns that job.

Privacy is the other limit. Prefer a local, in-browser tool over a service that uploads the file to generate a diff. Even then, do not paste keys, tokens, or private customer data. A local comparison reduces the risk; it does not make a secret safe to display on your screen in a shared room, or in a screenshot you might send later.

A practical example

A teammate pastes two versions of a YAML config into a chat and asks why production started behaving differently. Running git diff first would require finding the repo, guessing the right commit, and hoping the pasted text still matches a file on disk. An online diff answers the immediate question: a timeout changed, or a key was renamed.

Once you know the change, the follow-up belongs in Git: find the same file in the repository, make the edit on a branch, and open a review so the new value is not lost in a chat log. The browser tool found the difference; Git made it official.