Text Diff Checker
Compare two pieces of text and highlight the lines that were added or removed.
How to use the Text Diff Checker
Step 1 — Paste both versions
- Put the original on the left and the changed text on the right.
Step 2 — Compare
- Press Compare to run the line-by-line diff.
Step 3 — Read the result
- Green = added, red = removed, plain = unchanged.
- A summary counts the changes.
Private
- Everything runs in your browser; nothing is uploaded.
Frequently asked questions
Line by line. It finds the longest common sequence of lines and marks the rest as added (in the changed text) or removed (from the original).
Green lines were added in the changed version, red lines were removed from the original, and unchanged lines are shown plainly for context.
Yes. It works on any text, including source code, config files, and prose. Comparison is line-based, which suits code and structured text well.
Yes. A summary shows how many lines were added and removed, or tells you the two texts are identical.
No. The comparison runs entirely in your browser; neither version is sent anywhere.
About the Text Diff Checker
This tool compares two pieces of text and shows you exactly what changed between them, line by line. Paste an original and a revised version, and it highlights which lines were added, which were removed, and which stayed the same.
How the comparison works
The tool uses a longest-common-subsequence approach — the same core idea behind the diff tools built into version control systems. It finds the largest set of lines that appear, in order, in both versions, treats those as unchanged, and marks everything else as an addition or a removal. This produces an intuitive result: unchanged context stays put while genuine edits stand out, rather than the whole text appearing different because one line moved.
What it is good for
Comparing text is a constant need. Developers check what changed between two versions of a file, a config, or a snippet of code. Writers and editors compare drafts to see what was revised. Anyone can use it to spot the difference between two lists, two pasted emails, or two versions of a document. Because the comparison is line-based, it is especially clear for code and structured text where each line is a meaningful unit.
Reading the result
Added lines are shown in green with a plus sign, removed lines in red with a minus sign, and unchanged lines plainly so you keep your bearings. A summary at the top counts the additions and removals, or confirms the two texts are identical. For large texts the diff is computed instantly in your browser.
Privacy and related tools
Both versions stay in your browser and are never uploaded. To count words or characters in a single text, use the Word Counter; to format and validate JSON, use the JSON Formatter.