Free online tool
Text Diff Checker
Paste two versions of a text and see exactly which lines differ.
No differences yet.
Why compare texts?
Whether you're reviewing an edit from a colleague, comparing two configuration files, or checking that your paste operation kept every line intact, seeing the differences highlighted is far faster than scanning by eye. A diff tool is the go-to for developers, writers and QA teams alike.
How to use
Paste the original text on the left and the modified version on the right. Rows that differ are highlighted, so you can spot changes at a glance. Everything stays local to your browser.
+Does this do word-level diffs?
Not yet — it compares line by line, which is fast and covers most use cases. Word-level highlighting is on the roadmap.
+How large can the texts be?
For best performance, keep each side under about 5,000 lines. Beyond that the browser may slow down.
Spotting what actually changed between two drafts
A line-by-line diff catches things a side-by-side read-through misses after the third pass — a swapped word, a dropped negation like 'not', or a single trailing space that makes two lines that look identical register as different in version control.
Editors comparing a submitted manuscript against a previously approved version, legal teams checking a redlined contract against the original, and developers reviewing a config file change all rely on the same underlying idea: humans are bad at noticing what didn't change, and a diff tool is built specifically to highlight the opposite — what did.
Whitespace is a frequent false alarm
Copying text out of a PDF or a Word document often brings along non-breaking spaces or trailing whitespace that's invisible on screen but will flag every line as changed; if a diff looks unexpectedly noisy, that's usually the first thing to suspect rather than assuming the content itself shifted.
Reading the output without getting confused
Additions and removals are shown per line rather than per character in most cases, so a single word change inside a long paragraph will mark the entire line as modified — that's expected behavior, not a bug, and it's why keeping paragraphs to one sentence per line makes contract or policy comparisons far easier to audit.
Color coding conventions are fairly standard across diff tools — additions in green, removals in red — but it's worth confirming which side of the comparison is 'original' and which is 'revised' before reading the colors, since swapping the two inputs will flip the meaning entirely even though the visual output looks similar at a glance.
Practical use beyond writing
Comparing two versions of a terms-of-service page, a config file pasted as text, or a translated string table are all cases where a visual diff catches a one-character typo that would otherwise slip past a manual review, especially numeric values buried in the middle of a paragraph.
Students comparing their own paraphrase against a source passage sometimes use a diff to check how closely their wording overlaps before submitting, a rough self-check that's no substitute for a plagiarism detector but catches accidental copy-paste survivors.
A workflow tip for long documents
Breaking a long document into sections and diffing them one at a time, rather than pasting an entire 5,000-word contract at once, makes it much easier to isolate which clause actually changed instead of scrolling through a wall of green and red highlighting looking for the one line that matters.
Version history without a version control system
Teams that write in a shared document without formal version control — a Google Doc, a plain text file passed around over email — can use a diff tool as a lightweight substitute for 'track changes,' pasting the before and after into two boxes to see exactly what a collaborator altered without relying on comment threads or memory of who said what.
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