ProtoFluid

ProtoFluid is in early-access. There will be bugs.

Welcome

ProtoFluid delivers an in-document responsive design testing app that manages flexible <iframe> viewports, pop-up windows and even viewport <meta> mimicry.

Try it now — for free!

Take ProtoFluid for a spin on this website or hit download and trial it on one of your projects.

Download

Version: 0.0.9 | 12.8.2026

Gold sponsors

Become a sponsor — or perhaps — a hero?

ProtoFluid Pro + Add-ons

ProtoFluid Pro offers unlimited viewports, fullscreen mode and wake lock.

Add-ons will be arriving shortly.

Visit the shop

Effortless testing

ProtoFluid highlights neat responsive work that would otherwise be missed.
  • Extend your responsive visibility with parallel viewports.
  • Reduce cognitive overhead and preview style changes across breakpoints.
  • Spot issues early and avoid rework at the end of a project.

Feature highlights

  • Includes viewports for watches, phones, tablets and beyond.
  • Viewport <meta> mimicry enables on-phone testing.
  • Multi-browser, multi-frame and multi-window testing.
  • CSS-only refresh.
  • Color-scheme adjustment.
  • Scroll-to-bottom/top or even by selector.
  • Unpolluted HTML. Focus on inspecting yours.

Installation

Download and include the ProtoFluid folder in your project.

Visit the documentation for details.

ProtoFluid-button

ProtoFluid can be loaded on-demand via the <protofluid-button> component.

ProtoFluidButton.js weighs in under 600 bytes!

Visit the documentation for details.

The core ProtoFluid app is free

Silver sponsors

Interested in becoming a sponsor? Visit the sponsor page.

Privacy

ProtoFluid delivers private responsive testing.

It exists in the context of your project. It does not depend on a server and no trackers are used.

Check out the privacy policy for more detail.

Proudly independent

ProtoFluid is completely independent of big tech and is not available via any third party service.

Do not trust code hosted on GitHub, NPM or anywhere else.

Premium addons are only available in the ProtoFluid store.

Enhance your workflow

  • Accelerate design execution via parallel viewports.
  • Extend viewport heights. See more of your work.
  • Scalable viewports let you test large ‘screens’ on laptops.
Progress is easy to demonstrate and share.

Clients can far more easily grasp the core concept of responsive design when they can see the results.

Browser agnostic

The web is more than just Chromium 🤯

ProtoFluid is not limited to a single layout and rendering engine.

It allows you to use the browser, tools and extensions of your choice.

Maybe even Servo? One day…

Viewport meta mimicry

On mobile devices ProtoFluid lets you intuitively modify the viewport meta tag on-the-fly. This enables the testing of multiple viewports on a single device.

One ring phone to rule test them all.

A single device can mimic others. An iPhone and Android phone combo covers a significant amount of potential user devices.

Your phone is a device lab

There are significant benefits to testing via meta tag modification.

  • Testing takes place in realistic conditions.
  • Less device switching, charging and updating. Fewer cables!
  • Save electricity and reduce desk clutter.
  • Rapid viewport switching makes issues easy to spot.
This approach dramatically reduces testing hardware cost.