Side-by-Side Code Compare

Compare two text/code snippets side-by-side with synchronized scrolling.

File A

File B

Compare two versions of text or code, side by side

Code Compare Tool puts two blocks of text next to each other, labelled File A and File B, and highlights the rows that differ. It suits source code, configuration files, SQL, logs, or ordinary prose. Rather than flicking between two windows and hunting for the changed value by eye, you get coloured rows and a count of how many lines do not match.

How to run a comparison

Paste the first version into File A and the second into File B. Scrolling one box scrolls the other, which keeps long inputs lined up while you check what you pasted.
To see how it behaves first, press Sample to load a short four-line example. Clear empties both boxes.
Press Process Now. Two numbered panels appear, File A on the left and File B on the right, with a Mismatched Lines total above them.
Use Copy or Download to keep the panel text; the download is named result.txt.

Editing File B hides the previous results, so press Process Now again after changing either box.

How lines are matched

The tool pairs line 1 with line 1, line 2 with line 2, and so on down the page. When a pair is not identical, the A row turns red and the B row turns green. The test is exact: a changed indent, a trailing space or a different capital letter all count as differences. If one file is longer, its extra rows are counted as mismatches too. Angle brackets are escaped, so HTML or XML in either box is displayed as text instead of being interpreted.

Situations where it helps

Checking a staging configuration file against production to spot a single changed setting.
Confirming that a function you copied into a new file still matches the original after a refactor.
Comparing two exported lists or CSV headers to find the row where they diverge.
Reviewing the edits between two drafts of a short email template or policy paragraph.

Know the limits

Because comparison is by line position, inserting or deleting one line near the top pushes every later line out of alignment, and much of the file may show as different even though only one line changed. In that situation the Code Diff Checker is the better fit, since it looks ahead to recognise inserted and removed lines. Use this side-by-side view when both versions have the same structure and you want to see exactly which lines differ, and where in the file they sit.

Related Tools

Frequently Asked Questions

How does this tool decide that two lines are different?

It compares the text of line N in File A with line N in File B, character for character. Any difference, including indentation, trailing spaces or letter case, marks the pair as mismatched. Lines that exist in only one of the files also count.

Why is almost everything highlighted after I added one line?

Lines are compared by position, not by content. An extra line near the top shifts every following line down by one, so each pair no longer lines up. For that kind of change, use the Code Diff Checker, which detects inserted and removed lines.

Does it understand programming languages?

No. It treats both boxes as plain text and does not parse syntax, ignore comments or normalise formatting. That makes it work equally well on code, configuration, logs and prose, but it will flag purely cosmetic changes such as whitespace.

What does the synchronised scrolling do?

When you scroll File A or File B in the input area, the other box scrolls to the same vertical position. This keeps the two texts aligned while you paste and review them, which is useful for long files.

What is saved when I press Download?

A plain text file named result.txt containing the text shown in the result panels, including the line numbers. Copy places that same text on your clipboard. Neither option includes the red and green highlighting.