diffl

A web app for comparing two files and seeing exactly what changed. Paste text or upload plain text, Markdown or PDFs, and get a diff back.

The constraint that shaped it: everything runs client-side. Parsing, diffing and rendering all happen in the tab, in memory. There is no server to send a document to, because there is no server.

Two ways to read a diff

• Git-style — the familiar line-by-line view, with additions and deletions in place. Good when you want the context around a change.
• List of changes — only the differences, condensed. Good when the files are long and mostly identical.

What it tells you about the files

Reading time, character count and word count for each side, plus the numbers on the difference itself — lines changed and characters differing. Enough to answer “how different are these, really” before reading a single line of the diff.

Built with

Next.js 15 and TypeScript, Tailwind for styling, PDF.js for document parsing, and diff for the comparison itself. It deploys as a static bundle, which is the natural consequence of nothing needing to run server-side.