Compare two texts line by line

A diff shows exactly what changed between two versions of a text: lines that were added, removed or modified. It is the foundation of code review and version control, but you often need it outside a Git repository – comparing two configuration files from different servers, two API responses, a contract before and after edits, or the output of a command on two machines. Paste both versions and this tool highlights every difference, down to the individual characters that changed inside a line.

How it works

The comparison runs on our server with Python's difflib, the same algorithm family used by many review tools, which looks for the longest matching blocks and reports the minimum set of edits between them. The result is shown side by side, with line numbers, or as a unified diff – the format produced by git diff and diff -u – that you can copy or download as a .patch file and apply with git apply or patch -p0.

Options

Ignore whitespace treats lines that only differ in spaces or tabs as equal, perfect after a re-indent.
Ignore case is useful for SQL, HTTP headers or hostnames.
Only show changes collapses long identical stretches and keeps three lines of context around each change, so large files stay readable.

Practical examples

Configuration drift

Copy nginx.conf from staging and production into the two panes to find the one directive that differs. Enable Ignore whitespace if the files were edited with different editors.

Reviewing generated output

Before and after a dependency upgrade, compare the output of pip freeze or a build log to see exactly what moved.

Privacy

Texts are sent over HTTPS, compared in memory and immediately discarded; nothing is logged or stored on the server. Your inputs are remembered only in your browser's localStorage until you press Clear Data.