Diff Checker
Compare any two blocks of text or code side-by-side or in a unified view - the same GitHub/GitLab pull-request style diff you already know. Syntax highlighting, word-level change highlighting, and collapsed unchanged regions all run in your browser.
This is the general-purpose diff checker / text compare tool. For LLM prompt rewrites specifically, use the Prompt Diff Checker.
Diff
Paste or upload two files to compare them.
Paste or upload two files to compare them.
Frequently Asked Questions
Why does every line show as changed?
Almost always a line-ending mismatch (CRLF vs LF). Turn on Normalize line endings in Options - it is on by default - so the comparison ignores that noise.
Can I compare two files?
Yes. Use Upload Original and Upload Changed, or drag a text file onto either side of the diff editor.
Comparing two AI prompts specifically?
Try the Prompt Diff Checker, which also shows token savings. This Diff Checker is the general-purpose GitHub-style tool for any text or code.
Is my content uploaded?
No. Diff runs entirely in your browser with Monaco’s Diff Editor. Nothing is sent to a server.