Parallel · Aligned · Colour-coded
Side-by-Side Text Comparison
Updated: June 2026
A side-by-side comparison puts the original and the revised text in two parallel columns and keeps matching lines aligned across both. It is the most intuitive way to review changes, because for every line you can read the "before" on the left and the "after" on the right at exactly the same height.
Free · No upload · Aligned columns
How alignment works
The hard part of a two-column diff is keeping the columns in step. If five lines are inserted on the right, the left column needs five blank placeholders so the lines that follow stay opposite their counterparts. This tool handles that automatically: identical lines sit on the same row, and where one side has content the other lacks, an empty cell is drawn to hold the position.
The result is that your eye can travel straight across any row and trust that you are looking at the same logical line on both sides. Removed lines are shaded red on the left with an empty cell opposite; added lines are shaded green on the right with an empty cell opposite; edited lines show the old and new versions face to face with the changed words highlighted.
Side-by-side versus inline
| Side-by-side | Inline |
|---|---|
| Two columns, before/after in parallel | Single column, removed then added |
| Best on wide screens | Best on narrow screens and mobile |
| Great for reading full context | Compact, matches code-review style |
| Easy to see what replaced what | Easy to scan a long list of changes |
The tool offers both, and you can switch with a single click. Many people draft and review in side-by-side because it reads like a "track changes" layout, then flip to inline when they want a tighter overview or are working on a phone.
When side-by-side shines
- Reviewing edits to an article, where you want to read both versions in full.
- Comparing two configuration files where the structure matters and you need to see corresponding lines.
- Checking a translation against its source line by line.
- Proofreading a contract revision where context around each change is essential.
In all of these the parallel layout keeps the surrounding lines visible, so a change is never shown out of context.
Private and instant
The two-column view is rendered entirely in your browser. There is no server round trip, so the comparison appears the instant you stop typing, and nothing you paste is transmitted anywhere. Combined with the word-level highlighting and the ignore options for case and whitespace, you get a focused, accurate, and completely private side-by-side review.
Frequently asked questions
What is a side-by-side comparison?
It shows the two versions in two parallel columns, with matching lines aligned across both sides so you can read the before and after of every change at the same horizontal position.
When should I use inline view instead?
Inline view stacks removed and added lines in a single column, which fits narrow screens and mobile better and matches the way code review tools show diffs.
Does it align the unchanged lines?
Yes. Identical lines sit at the same row on both sides, and gaps are inserted where one side has a line the other does not, keeping the columns in step.