API Reference

One endpoint. HTML in, shareable link out.

Base URL

https://gui.new/api

POST

/canvas

Create a new canvas. Returns a shareable URL.

Request Body

Field	Type	Required	Description
html	string	Yes	HTML content (max 2MB)
title	string	No	Display name in toolbar & OG image
frames	array	No	Multiple HTML variants as tabs. Each: {html, label?}

Example

curl -X POST https://gui.new/api/canvas \
  -H 'Content-Type: application/json' \
  -d '{
    "title": "My Dashboard",
    "html": "<h1 style=\"color:white\">Hello World</h1>"
  }'

Response

{
  "id": "abc123xyz",
  "url": "https://gui.new/abc123xyz",
  "edit_token": "tok_...",
  "expires_at": "2026-02-28T16:00:00Z"
}

PUT

/canvas/:id

Update an existing canvas. Requires edit_token. All viewers see changes live via SSE.

Headers

Header	Value
Authorization	Bearer <edit_token>

curl -X PUT https://gui.new/api/canvas/abc123xyz \
  -H 'Content-Type: application/json' \
  -H 'Authorization: Bearer tok_...' \
  -d '{"html": "<h1>Updated!</h1>"}'

GET

/canvas/:id/events

Server-Sent Events stream. Receive real-time updates when canvas HTML changes.

const source = new EventSource(
  'https://gui.new/api/canvas/abc123xyz/events'
);

source.addEventListener('update', (e) => {
  const { html } = JSON.parse(e.data);
  // Re-render with new HTML
});

Built-in Features

Every canvas automatically gets:

Multiplayer cursors— All viewers see each other's cursors, names, and colors

Input sync— All form inputs, sliders, toggles sync across viewers in real-time

State persistence— Form state saves to database — survives after all viewers leave

Component library— <gui-chart>, <gui-table>, <gui-kanban>, <gui-timeline>, <gui-form>, <gui-card>, <gui-grid>, <gui-code> — auto-injected

OG images— Dynamic social preview with canvas title and metadata

Limits

Feature	Free	Pro
Auth	None — just POST	API key via `Authorization: Bearer`
Rate limit	5 creates / hour	100 creates / hour
Max size	2 MB	10 MB
Expiry	24 hours	14 days
Edits	3 per canvas	Unlimited
Visibility	Public only	Public or private (password-protected)
Watermark	gui.new badge	No watermark

Free tier requires no account or API key. Rate limited by IP address.

SDKs

JavaScript / TypeScript

npmjs.com →

npm install gui-new

import GuiNew from 'gui-new'

const gui = new GuiNew()
const canvas = await gui.create({
  title: 'My Dashboard',
  html: '<h1>Hello</h1>'
})
console.log(canvas.url)

Python

pypi.org →

pip install gui-new

import gui_new

canvas = gui_new.create(
    "<h1>Hello</h1>",
    title="My Dashboard"
)
print(canvas.url)

Stratus LabsQuestions? @guidotnew