Diff Checker compare
Compare two blocks of text line by line and highlight added and removed lines.
What this tool does
Working out what changed between yesterday and today in a configuration file, where two servers diverge, or how a response changed after a deployment is a routine task. Reading long text side by side is error prone, and whitespace or ordering differences are especially easy to miss.
This tool compares two texts line by line and marks added lines, removed lines, and unchanged lines, in the same style as a Git diff. It is useful for material that never reaches version control, such as scratch files, API responses, and log excerpts.
Comparison happens in the browser, so pasting configuration files or logs does not transmit them anywhere.
When to use it
Use it to find differences between per-server configuration files, to compare API responses before and after a release, to see what a colleague changed in a revised file, or to contrast two sections of a log.
Input and output examples
Original port=8080 and debug=false versus revised port=9090 and debug=false
Removed port=8080, added port=9090, debug line unchanged
Only the changed line is reported.
Notes and limitations
Comparison is line based, so changing a few words within a line marks the whole line as removed and added. Trailing whitespace and differing line endings (CRLF versus LF) can also report every line as different even when the content matches; normalise whitespace first in that case. For data where ordering is not meaningful, such as JSON, sort or format both sides before comparing so key order alone does not produce noise.
Frequently asked questions
Identical content shows as entirely different.
Line endings differ (Windows CRLF versus Unix LF) or lines carry trailing whitespace. Normalise and compare again.
Can it compare word by word?
This tool compares whole lines, so a partial change within a line marks the entire line as changed.