Text Difference Checker
Put two versions of a text side by side and see exactly which lines were added, removed or left alone.
Results
What this tool does
Two drafts of the same letter, two versions of a clause, the file before and after someone else touched it: reading them side by side and spotting the change is slow and unreliable. This page uses the same method as the diff tools programmers have used for fifty years — it finds the longest run of lines the two versions have in common, and everything outside that is the change. Nothing leaves your browser, which matters when the two things are contracts.
Formula
finds the longest common subsequence between the two versions ; what is left over is what changed
Variables
| Symbol | Meaning | Unit |
|---|---|---|
text_a | The first text | — |
text_b | The second text | — |
OUT | What changed | — |
SA | Lines that stayed | — |
RM | Lines taken out | — |
AD | Lines put in | — |
CH | Lines touched in all | — |
ID | They are identical | — |
UN | Of the result that is unchanged | % |
Worked example
- The first textDear Ana, The meeting is on Tuesday at ten. Please bring the quarterly figures. Thanks, Paulo
- The second textDear Ana, The meeting is on Wednesday at ten. Please bring the quarterly figures. The room has changed to 2B. Thanks, Paulo
- What changed Dear Ana, - The meeting is on Tuesday at ten. + The meeting is on Wednesday at ten. Please bring the quarterly figures. + The room has changed to 2B. Thanks, Paulo
- Lines that stayed6
- Lines taken out1
- Lines put in2
- Lines touched in all3
- They are identicalNo
- Of the result that is unchanged66.7 %
Limitations
- The calculation runs entirely in your browser. The values you type are never sent to a server.
Frequently asked questions
How do I read the result?
Lines with two spaces in front are in both versions. A minus means the line is in the first text and gone from the second; a plus means it is new in the second. An edited line shows up as a minus and a plus together, because the comparison works by whole lines — it can tell you a line changed, not which word inside it moved.
Is my text sent anywhere?
No. The comparison runs in this page, in your own browser, and nothing is uploaded — which matters more here than on most pages, because the two things people most often compare are contracts and code. You can switch the network off and it will keep working.