Text Diff Checker
Compare two texts online with line-by-line diff highlighting — side by side or unified, instantly inside your browser.
What is a text diff checker?
A diff checker compares two versions of a text and highlights exactly which lines were added, removed, or left unchanged between them — the same kind of comparison a version control system shows for a code change, applied to any plain text. It turns "these two blocks of text are different somehow" into a precise, line-by- line account of what actually changed.
It's useful for comparing two drafts of a document, checking what changed between two versions of a config file, or spotting an accidental edit in a block of text that looks nearly identical to the original at a glance.
GuideHow to use it
How the comparison works
Both texts are split into lines and compared using a longest-common-subsequence algorithm — the same underlying approach most diff tools use — to find the smallest possible set of additions and removals that turns the original into the changed version. "Side by side" shows both versions in parallel columns with matching lines aligned; "Unified" shows a single combined view with removed lines marked − and added lines marked +. "Ignore case" and "Ignore whitespace" let minor formatting differences be treated as no change at all.
Why it helpsFeatures & benefits
Why this runs entirely in your browser
Text compared here can include unpublished drafts or private notes, so nothing is uploaded. The diff is computed in JavaScript locally in the tab, which means it keeps working offline once the page has loaded and nothing pasted into it persists after the tab is closed.
Common uses
Comparing two drafts of an article to see exactly what an editor changed, checking the difference between two versions of a config or data file, verifying that a find-and-replace only touched the lines it was supposed to, or spotting a subtle edit in text that otherwise looks unchanged.
Frequently asked questions
A few things people usually want to know before trusting the numbers.
Side-by-side shows both texts in parallel columns with matching lines aligned. Unified combines them into a single view, marking removed lines with − and added lines with +.
It trims each line and collapses repeated spaces before comparing, so differences in indentation or spacing alone don't count as a change.
Comparing very long texts requires checking a large number of line combinations, which is capped to keep the browser responsive. Try comparing smaller sections instead.
Line-by-line — each line is treated as a single unit when finding what changed, the same way most text diff tools work.
No. All comparison happens locally in your browser. Nothing typed or pasted here is sent to a server, stored, or shared.