How to compare two versions of a text

Two drafts, two config files, two copies of a contract. Reading both is slow and unreliable; comparing them is neither.

People are poor at spotting differences by reading. A single changed digit in a long document is nearly invisible, and it is often the one that matters.

Step-by-step

1. Paste the original on the left.
2. Paste the new version on the right.
3. Read the marked differences — added, removed and changed.

Reading the result

Lines present only in the new version are additions; lines only in the original are deletions. A line that was edited is shown once, with only the words that actually differ marked — struck through where they went, highlighted where they arrived.

That distinction matters. A line-only comparison reports a changed sentence as one line removed and one line added, which is true and tells you nothing: you still have to read both and find the difference yourself. Changing "within 14 days" to "within 30 days" is one word, and that is what it should say.

The summary counts words rather than lines for the same reason — three lines changed does not separate a typo from a rewrite. Underneath it, the words that went and the words that arrived are listed outright, with a count where one appears more than once.

Punctuation and spacing

Punctuation is counted and named separately from words, because removing a comma and removing a word are not the same finding — only one of them changes what the sentence says. The marks are listed by name rather than as bare glyphs, since a lone comma in a list is hard to read.

Spacing is reported too. A double space, a tab where a space was, or a non-breaking space are all invisible on screen and real in the file, and they are exactly the differences that survive a careful read-through.

Characters that look almost identical

The hardest difference to see is a character swapped for one that looks the same. A straight apostrophe against a curly one, a hyphen against an en dash, straight quotation marks against curly ones — these are different characters that render almost identically, and they are called out by name.

This matters beyond tidiness. An exact-match search, a lookup key, a spreadsheet filter or a comparison in another system will treat the two as different, so a document that looks unchanged can behave differently. Where a line differs only in this way, the tool says the difference is typographic rather than reporting words as changed.

Words that moved

When a word appears in both the removed and the added list it was reordered or reworded rather than being new, and the tool says so. Rearranging a sentence otherwise reads as a large change when nothing was actually added or taken away.

What it is good for

• Contract versions where you were told "only minor changes".
• Config files between a working and a broken environment.
• Drafts returned without tracked changes.
• Checking a copy-paste actually copied everything.

Whitespace

Trailing spaces and different line endings produce differences you cannot see, which is confusing when two lines look identical and are marked as changed. If everything appears different, suspect line endings — a file written on Windows and one written on a Mac differ on every single line.

Frequently asked questions

Does it detect punctuation changes?

Yes, counted and named separately from words — a removed comma is reported as a comma rather than being folded into a word count. Spacing is reported too, including tabs and non-breaking spaces, and characters that look almost identical such as a curly apostrophe replacing a straight one are called out by name.

Does it show which words changed, or only which lines?

Words. A line that was edited is shown once with the differing words marked in place, and the words that went and arrived are listed separately. Only whole lines that were added or removed outright are shown as whole lines.

Is my text uploaded?

No. Both versions are compared in your browser and neither is transmitted.

Why is every line marked as different?

Almost certainly different line endings between the two sources — one written on Windows, the other on a Mac or Linux. The visible text is identical; the invisible characters at the end of each line are not.

Can I compare two files rather than pasting?

Paste the contents of each. For very large files, comparing the relevant sections is usually more informative than the whole thing anyway.