Developer Tool — Case study

DiffMergy — developer tool, live in production.

A browser tool for comparing, diffing and merging two files line by line, with everything running client-side so nothing sensitive ever leaves the machine.

ClientDiffMergy
IndustryDeveloper tools
Timeline4 weeks to public launch
Live atdiffmergy.com
◆ Client-side diff algorithm◆ Web workers◆ File export◆ Zero-backend architecture
The problem

What was broken

Developers often need a quick diff but will not upload proprietary code to a server, install a desktop app, or create yet another account just to compare two files. The tools that existed all asked for one of those.

Results

  • Zero server upload — code never leaves the browser
  • Word-level inline diff highlighting
  • Merge and export in one view
  • No sign-up, no install, instant load
What we built

Decisions that made the difference.

/01

Runs entirely in the browser

No upload endpoint and no server round-trip. Files are read locally and the diff is computed in the tab, so source code never leaves the machine.

/02

Line- and word-level clarity

Added, removed and changed lines are colour-coded with inline word-level highlighting, so small edits stand out instead of drowning in noise.

/03

Merge, not just compare

Beyond viewing changes, users pick which side wins per block and export the merged file directly from the same view.

/04

Zero friction by design

No sign-up wall, no file-size trap, no setup. Open the page, paste two files, done — which is why people actually keep using it.

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