How does the diff work?

The tool compares text line by line using a longest common subsequence algorithm. Lines present only in the original are shown in red, lines only in the modified version are shown in green, and unchanged lines are shown in grey.

Does it support character-level diff?

The current view shows line-level differences. Lines that differ are marked as removed and added, making it easy to spot changes across any block of text.

Is there a size limit on the text I can compare?

No hard limit is enforced, but very large texts (thousands of lines) may take a moment to process as the diff runs entirely in your browser.

Can I use the diff checker to compare code or config files?

Yes. Paste any two blocks of text — source code, JSON configs, YAML files, SQL queries, or plain prose. The line-by-line diff works the same regardless of content type.

What do the colours in the diff output mean?

Green lines are present in the second block but not the first (added). Red lines are present in the first block but not the second (removed). Unchanged lines appear without a colour highlight.

Private by defaultRuns in your browser

Diff checker

Paste original and modified text to see exactly what changed — added, removed, and unchanged lines.

Original1 lines

Modified1 lines

Quick samplesUseful for testing

Diff Checker

About this tool

Paste two texts to see line-by-line differences with added and removed lines highlighted. Works on code, JSON, config, or prose — no signup needed.

Paste original and modified text to see exactly what changed — added, removed, and unchanged lines.

No signup requiredRuns in your browserInstant results

How to use

1
Paste your original text in the left panel and the modified text in the right panel.
2
Differences are highlighted instantly — green for additions, red for deletions.
3
Use it to compare code snippets, config files, or any two blocks of text.
4
Scroll through the diff to review every changed line.

Why use this tool?

→
Compare two versions of a config file, script, or document to find what changed.
→
Review code changes when you don't have access to a version control diff view.
→
Verify that a copied or generated text matches the original with no unexpected edits.

ExamplesInput → output

Spot a changed word

Input

Left: The quick brown fox
Right: The slow brown fox

Outputquick → slow highlighted as changed

Added line

Input

Left: line1
line2
Right: line1
line2
line3

Outputline3 highlighted as added

Frequently asked questionsCommon questions answered

These answers explain common diff checker tasks, expected input formats, and edge cases so both visitors and search engines can understand what this tool does.

How does the diff work?: The tool compares text line by line using a longest common subsequence algorithm. Lines present only in the original are shown in red, lines only in the modified version are shown in green, and unchanged lines are shown in grey.
Does it support character-level diff?: The current view shows line-level differences. Lines that differ are marked as removed and added, making it easy to spot changes across any block of text.
Is there a size limit on the text I can compare?: No hard limit is enforced, but very large texts (thousands of lines) may take a moment to process as the diff runs entirely in your browser.
Can I use the diff checker to compare code or config files?: Yes. Paste any two blocks of text — source code, JSON configs, YAML files, SQL queries, or plain prose. The line-by-line diff works the same regardless of content type.
What do the colours in the diff output mean?: Green lines are present in the second block but not the first (added). Red lines are present in the first block but not the second (removed). Unchanged lines appear without a colour highlight.