A Mac app for the HTML apps your AI agent builds.

Plopp gives each app its own storage, file access and a tab. Your data stays on your Mac. Open your apps from your other Macs over Tailscale.

Coming soon for Mac View the source on GitHub

Free and open source · macOS 14 or later · Apple silicon and Intel

How it works

You ask. Your agent builds. Plopp keeps it.

An agent can write a good small app in one go. Plopp is where that app lives after the chat ends.

Ask your agent for an app

Claude Code, Codex or any agent that can write files. The Plopp skill tells it how a Plopp app looks.

npx skills add plopphq/skills

The agent writes a bundle

A folder that ends in .plppx, with an index.html and anything else the app needs.

Budget.plppx/
  index.html
  app.js
  plopp.json

Plopp opens it

The app appears in your library. Double-click opens it in a tab. Everything it saves stays on your Mac.

plopp add Budget.plppx
✓ Budget is in Plopp

What each app gets

The parts a browser tab does not give you.

The app stays plain HTML. Plopp adds what it needs to be useful for more than one afternoon.

Storage that lasts

localStorage works with no code change. Plopp keeps the data in a database file per app, and every open view of the app sees the same data.

~/Plopp/.data/com.example.budget/kv.sqlite

Access to your files

Each app has its own file area. It can ask for one more folder, and you decide in a sheet. You can remove the access in Get Info.

plopp.files.write("@exports/march.csv", data)

A tab of its own

Apps open in tabs, like documents. Each app runs on its own origin in a sandbox, so one app cannot read another app's data.

⌘← ⌘→ switch tabs · ⌘W close

Your other Macs

Let Plopp run on a Mac mini and open its apps from your MacBook. The connection goes over your own Tailscale network, not through a cloud.

Hosts → Mac mini · 100.101.12.4

Local first

Your apps and your data are files on your Mac.

The library is a normal folder. You can see it in Finder, back it up with Time Machine and move it to another Mac. Plopp has no account and no cloud.

Apps are folders in ~/Plopp. Plopp never changes them.
Data is in a separate folder per app, so a new version of an app keeps your data.
Delete an app and it goes to the Trash with its data. Put Back restores both.

~/Plopp/
  Budget.plppx — the app
  Todo.plppx
  Reading List.plppx
  .data/
    com.example.budget/ — its data
      kv.sqlite
      files/
  .trash/

$ plopp new habits
created Habits.plppx
$ plopp validate Habits.plppx
✓ index.html · ✓ plopp.json · ✓ 214 KB
$ plopp dev Habits.plppx
serving with live storage at 127.0.0.1:51824
$ plopp add Habits.plppx
✓ Habits is in Plopp

Made for agents

A CLI and a skill, so agents get it right the first time.

The plopp command makes, checks, tests and adds apps. The skill teaches your agent the format, the storage and the Mac look. Both are open source.

Works with Claude Code, Codex, Gemini CLI, Cursor and other agents that read Agent Skills.
An MCP server and plugins for Claude Code and Codex come next.

Examples

Apps you can ask your agent for.

See all examples

Example

Budget

Household spending by month, with CSV export.

Example

Habit Tracker

Daily streaks for a few habits.

Example

Reading List

Links to read later, with tags.

Example

Packing List

One list per trip, ticked off on the way.

Open source

Free, open source, and yours to change.

The app, the CLI, the skill and the format are on GitHub under the Apache-2.0 licence. Read the code, report a bug or build a feature.

View on GitHub

plopphq/ploppthe Mac app

plopphq/clithe plopp command

plopphq/skillsthe agent skill

plopphq/mcpMCP server · next

Questions

Short answers.

Does my data leave my Mac?

No. Plopp keeps apps and data in folders on your Mac. It has no account and no cloud service. Only when you open an app from another Mac does the data go over your own Tailscale network.

Which agents work with Plopp?

Any agent that can write files. The Plopp skill works with agents that read Agent Skills, for example Claude Code, Codex, Gemini CLI and Cursor.

Can I open a Plopp app in a browser?

An app that keeps its data only in localStorage also runs in a browser. Storage that lasts, file access and tabs come from Plopp, so a .plppx bundle is made to open in Plopp.

Do I need Tailscale?

Only to open your apps from another Mac. On one Mac, Plopp works without it.

Windows or Linux?

Plopp is for the Mac first. Windows and Linux can come later.

Give your agent's apps a home.

Free and open source. For macOS 14 or later.

Coming soon for Mac