An HTML file that saves itself

Hyperclay Local is a free, source-available desktop app that runs a tiny server on your machine.

No database. No build step. No backend.

Free to use, source available. No account required. Works offline.

Hyperclay Local menu-bar app: localhost:4321 served from ~/HyperclayApps/local-hyperclay-apps, synced two minutes ago as @panphora, with the Serve and Sync switches on.

Point it at a folder

Pick a folder inside your home folder. On first setup, Hyperclay Local starts serving it automatically. Open a malleable document in the workspace or your browser, edit it, and save back to disk. Get started.

A file that remembers

An HTML file can do almost anything. It can lay out an interface, run JavaScript, call browser APIs, and respond to every click and keystroke.

The one thing it cannot do is remember. Close the tab and every change is gone.

A malleable document fixes that. It serializes its own DOM and posts it to a local server, which writes it back to the file on disk. Open it again and your changes are still there.

That makes one file a complete application. Its layout, its logic, and its data all live in the same document. You can email it, commit it to git, or drop it in Dropbox, and it still works.

What the app actually does

ClayJS prepares your page's HTML and sends it to Hyperclay Local. The local server writes the document back to its file and keeps version history on disk. Read how saving works.

See what you can build

These are not screenshots. Every app below is a single HTML file running live in this page. Type in the wiki, check off a to-do, change a number in the budget and watch the total update. Run the same file under Hyperclay Local and every change saves itself to disk.

budget.htmlsaved

Item	Cost

Rent
Groceries
Coffee
Internet
Total

Why not a static file, localStorage, or a backend?

A static file can't save. Open one from disk and every edit vanishes on refresh. Hyperclay Local gives that same file one new power: it can write its own changes back.
localStorage is trapped. Its data lives inside one browser profile, in a form you can't read, and clearing your browser wipes it. Here the data is the file. Open it in any editor and it's all there, in plain HTML.
A backend is a lot to own. A database, a server, a build, a deploy, a host. This is one file and a local process. When you want more, sync to hyperclay.com is one toggle, and it stays off until you turn it on.

What you get

Inspect everything. Right-click, View Source, and the whole app is in front of you. Interface, logic, and data in the same markup. Nothing minified away or hidden behind a bundler.

Backups on every save. Before the server overwrites a file, it keeps the previous version. If a save goes wrong, the last good copy is still on disk.

Works offline. The server and your files both sit on your machine. No internet needed to run the app or edit your files.

No accounts, no telemetry. Local editing sends nothing anywhere: no analytics and no telemetry except an update check. No sign-up to edit your own files.

Extra features

Tailwind CSS on save. Point a stylesheet at /tailwindcss/{yourFileName}.css and the server compiles Tailwind on every save, including only the utilities that file actually uses. No build step to run yourself.
Cloud sync, if you want it. Turn on sync to mirror your folder to your hyperclay.com account and back. It is off by default, the API key is encrypted with your OS keychain, and your files work exactly the same with it off.
ClayJS. Type directly into a heading, format a note, or fill in a form. ClayJS can save the text and field values as part of the document. Build your first editable file.

Download

Desktop app for macOS, Windows, and Linux. Free to use, source available, no account required. It is an Electron app, so each download is around 100 MB.

macOS Apple Silicon HyperclayLocal-1.34.0-arm64.dmg 119.1 MB
macOS Intel HyperclayLocal-1.34.0.dmg 125.6 MB
Windows 64-bit HyperclayLocal-Setup-1.34.0.exe 102.9 MB
Linux x86_64 AppImage HyperclayLocal-1.34.0.AppImage 140.8 MB
Linux ARM64 AppImage HyperclayLocal-1.34.0-arm64.AppImage 140.6 MB

Source code: github.com/panphora/hyperclay-local

FAQ

How does the saving actually work?

ClayJS prepares your page's HTML and sends it to Hyperclay Local. The local server writes the document back to its file and keeps version history on disk. Read how saving works.

Is it safe to run?

The app uses several layers of protection:

Sandboxed renderer. Web content runs in an isolated Electron context, separate from the main process.
IPC security. The renderer and main process talk over secure Electron IPC channels.
Path traversal protection. The server validates every file path so nothing can be written outside the selected folder.
Filename sanitization. Saved filenames allow only letters, numbers, hyphens, and underscores.
Versioned backups. The server keeps the previous version of a file before it overwrites.

The app's source is public. You can audit the full codebase at github.com/panphora/hyperclay-local.

Do my files ever leave my machine?

No. Local editing is entirely on your computer, with no analytics and no telemetry except an occasional update check. The only time a file leaves is if you turn on cloud sync yourself, which pushes to your own hyperclay.com account. It stays off until you enable it.

Do I have to use ClayJS?

No. ClayJS provides editing and saving, but you can write your own client using the same save endpoint. Your document stays an HTML file.

Setup and troubleshooting

For installation and saving issues, see Troubleshooting. For folder setup and port conflicts, see Folders and ports.

Linux says permission denied

AppImage files need to be marked as executable:

chmod +x HyperclayLocal-*.AppImage

The app is the file. Read it, edit it, save it, or walk away with it.

Most tools sit between you and your work. Hyperclay Local does not: one file on your disk, yours for as long as you keep it. Frontend and done.