Diff checker

What people actually paste into a diff tool

Configuration files. Contract drafts. Two API responses that should be the same and are not. Environment variables. Code from a colleague. Almost none of it is material anyone would deliberately upload to a website they had never heard of, and almost all of it gets pasted into one anyway, because comparing two things by eye is genuinely hard and the tool is right there.

This one runs in the tab. There is no request to make and nowhere for the text to go, which you can confirm in about five seconds with the Network tab open.

Why a modified line shows as two changes

A line-based diff has exactly two operations: a line is present or it is not. When you edit a line, the old one is gone and a new one stands where it was, so it appears as a removal immediately followed by an addition.

That is not a limitation being worked around — it is how git, diff and every code review tool describe the same edit. Once you read the pair as "this became that", the output stops looking noisy.

The whitespace option is for reformatting

The most common reason two documents look entirely different while being substantially the same is that one has been reindented — tabs to spaces, a formatter run over it, an editor trimming trailing whitespace on save. Strictly, every line changed. Usefully, nothing did.

Ignoring whitespace collapses that noise so the real edits surface. It is the difference between a diff with four hundred changed lines and one with the two that matter.

Why it stays fast on long files

Finding the smallest set of edits between two documents means comparing every line of one against every line of the other — a table with one cell per pair. Two thousand lines against two thousand is four million cells, and ten thousand against ten thousand is a hundred million, which is enough to lock up a phone.

Real edits are almost never spread through a whole file, though: they are a small change somewhere in the middle of two mostly identical documents. So the matching beginning and end are trimmed off first and the expensive search only ever covers the part that actually differs. A one-line change in a five-thousand-line file is found in milliseconds rather than seconds.

Questions

How do I compare two pieces of text?

Paste one into each box. Lines that were removed are marked in red, lines added in green, and long runs of identical text are collapsed so the differences are not buried. Everything happens in this tab — nothing is sent anywhere.

Is my text uploaded?

No. That matters here more than it looks: the things people compare are configuration files, contracts, API responses and code, which are exactly the documents that should not be pasted into an unknown server. Open the Network tab and watch nothing leave, or disconnect entirely — it still works.

Why is a changed line shown as a removal and an addition?

Because a line diff works on whole lines. There is no such operation as "changed" — a modified line is the old one gone and a new one in its place, which is also how git and every other line-based tool describes it.

What does "ignore whitespace" actually ignore?

Leading and trailing spaces, and runs of spaces or tabs collapsed to one. It is the option to reach for when a file has been reindented or reformatted and you want to see whether anything real changed underneath.

Does it handle Windows and Unix line endings?

Yes, and it treats them as identical. A file saved on Windows and the same file saved on a Mac differ in every single line by the strictest reading, which is never what you want to be told, so line endings are normalised before comparing.

How large a document can it handle?

Comfortably into the thousands of lines. Comparing two long documents naively needs a table with one cell per pair of lines — a million cells for two thousand-line files — so the identical beginning and end are trimmed away first and only the part that genuinely differs is searched.

What BriskFile will not do to you

• Your files never leave your device

  Every conversion runs in your browser. Open DevTools, watch the Network tab, and you will see no upload — because there is not one.

• No account, no email, no watermark

  Nothing to sign up for and nothing stamped on your images. There is no step between choosing a file and getting it back.

• No limits at the download button

  No daily cap, no file counter, no "upgrade to download". If the tool starts a job, it finishes it.

• Checkable, not just claimed

  Open the Network tab and convert something — nothing goes out. Or load the page, disconnect, and watch it keep working: the tool is already on your machine, and your file never leaves it.