longest-common-subsequence line diff · − removed from A · + added in B · fast fallback for very large texts
Similarity0%MULTISET OVERLAP
Only in A0PAINTED RED
Only in B0PAINTED BLUE
Shared lines0PRESENT IN BOTH
✱ Text Tools · Group 08 of 09
Text Comparison.
Put two texts side by side and watch the differences surface on their own — unique lines painted red and blue in each pane, a line-numbered unified diff below, and a duplicate hunter for the copies hiding inside a single text. The badge in the middle keeps score as you type. Nothing is uploaded, nothing is stored.
Tools03
Comparisonlive
Uploads0
Backendnone
Costfree
Text Compare✱Duplicate Line Finder✱Diff Viewer✱Word Counter✱JSON Formatter✱Regex Tester✱Image Compressor✱BMI Calculator✱Color Picker✱Lorem Ipsum✱
In order, 01 → 03
What each tool reveals, with examples.
( 01 )
A symmetric, live comparison of two texts. As you type, every line that exists only in A is painted red and every line that exists only in B is painted blue — no button press needed. The score badge reports multiset similarity, the stat strip counts what's unique and shared, and "⧉ unique" copies either side's exclusive lines in one click. Two toggles shape the matching: Aa for case-sensitive comparison and ⌫ for trimming line edges first.
Example
A: "red apple / green pear"
B: "red apple / yellow plum"
↓
50% similar — "red apple" is shared; "green pear" paints red in A, "yellow plum" paints blue in B.
Use it for version checksedit reviewcontract comparisoncopy audits
Hunts repeated lines inside a single text. Every line that appears more than once gets a row in the results panel — with its count, every line number where it occurs, and a jump button that selects the first occurrence in the editor. All instances of a duplicated line are painted red in the pane, so repeats are visible at a glance. Blank lines are never reported, and the Aa / ⌫ toggles control how strictly lines are matched.
Example
apple
banana
apple
cherry
apple
↓
×3 "apple" at #1 · #3 · #5 — one row in the panel, all three copies painted in the editor.
Use it for log preplist cleaningdata auditskeyword dedupe
The directional story of the change from A to B, told the way code review tells it. The engine aligns both texts with a longest-common-subsequence algorithm, then walks them line by line: kept lines carry numbers on both sides, removals are marked − in red, additions + in blue. The same lines are painted in the panes above, and the whole diff can be copied as plain text for a commit message or changelog.
Example
A: "The lamp was trimmed at six o'clock."
B: "The lamp was trimmed at seven o'clock."
↓
− The lamp was trimmed at six o'clock.
+ The lamp was trimmed at seven o'clock.
one removal, one addition, numbered on both sides.
Use it for changelogscode reviewedit trackingrelease notes
Comparison rules · lines are the unit everywhere · compare & duplicates honour the Aa (case) and ⌫ (trim) toggles · the diff always compares raw lines · blank lines are never reported as duplicates · similarity = shared line copies ÷ total line copies across both texts · diff uses LCS alignment, with a fast multiset fallback for very large texts · swap never loses text — it only trades panes
The privacy promise
Compare anything. We couldn't read it even if we wanted to.
This page has no backend and no database. Every difference you just saw highlighted was computed by JavaScript inside your own browser tab — your texts never traveled a single centimeter of cable. Close the page and they're gone for good.
TEXT A + TEXT B→COMPARED IN YOUR BROWSER→THE DIFFERENCE
✕ SERVER · DATABASE · LOGS · ANALYTICS
Databasenull
Backendnone
Text uploads0
Session logs0
Questions
Asked often, answered plainly.
( 02 )
What exactly does the similarity % mean?
It's the multiset overlap of normalized lines: the number of shared line copies divided by the total number of line copies across both texts. 100% means both panes hold the same bag of lines; 0% means they share nothing at all. Repeated lines count each time, so a text padded with duplicates scores accordingly.
What's the difference between Text Compare and Diff Viewer?
Compare is symmetric — it paints what's unique in each pane and gives you counts and a similarity score, without claiming which text came first. Diff is directional storytelling — it walks from A to B and lists removals, additions and kept lines in reading order, exactly like a code review. Same data, two different questions.
Does the Duplicate Line Finder compare across the two panes?
No — it hunts inside Text A alone, reporting every line that appears more than once with its count and exact positions. For cross-text repetition, switch to Text Compare: any line present in both panes is counted as shared and left unpainted.
Is the text I paste saved anywhere?
No. IrisTool has no backend and no database. All comparison runs inside your browser tab and disappears the moment you close or refresh the page. There is nothing to leak, because nothing is ever collected.
Can I use these tools offline?
Yes. Once the page has loaded, every tool on it keeps working offline, because all the logic runs locally in your browser.