UUUP Tools

Developer Tools

Web Sandbox — HTML, CSS, and JS Preview

Edit and preview mixed HTML, CSS, and JavaScript inside an isolated iframe on the page. Useful for validating small frontend snippets without opening a local project.

Quick switch→HTML Minifier
HTMLSandboxPreview
Quick switch:HTML MinifierCSS Grid GeneratorFlexbox Generator

Favorite this tool

No favorite storage mode has been selected.

Quick actions

Back to Developer Tools Browse all tools

Copy this tool URL or open the system share sheet on a supported device.

Use cases

  • Verify a small HTML or CSS change
  • Demo a short interactive snippet
  • Build a minimal repro before debugging styles

How to use

  1. Write HTML, CSS, and JS in the editor
  2. Run or save to refresh the preview
  3. Iterate until the output looks right

Example input and output

Mix body

<h1 style="color:red">HI</h1>

Frame

Renders red text with attached JS on the node.

FAQ

Can it make network requests?

The preview runs in a restricted sandbox iframe, so cross-origin requests usually fail. It is best for static markup and local scripts.

How is this different from an online IDE?

It targets instant short-snippet preview, not full project dependency management or multi-file workspaces.

Tools

Related tools

Continue with another translated tool for a nearby task.

HTML Minifier

HTML Minifier for Extra Whitespace Cleanup

Available

Minify HTML fragments locally by removing extra whitespace and line breaks. Useful for template cleanup and size comparison without uploading markup.

HTML Minifier
Open tool

CSS Grid Generator

CSS Grid Generator — Rows, Columns, and Gaps

Available

Set column and row counts plus gaps to generate a basic display:grid layout. Preview the track structure, try quick templates, and copy CSS or HTML for admin layouts and card grids.

CSS Grid Layout
Open tool

Flexbox Generator

Flexbox Generator — Visual One-Dimensional Layout

Available

Tune flex-direction, justify-content, align-items, wrap, and gap with a live preview. Add or remove boxes to see wrapping and spacing, then copy the generated CSS (and HTML scaffold) into your project.

Design CSS Layout
Open tool