Polypane Web Browser

What is Polypane?

Polypane is a specialized, proprietary web browser designed specifically for web developers and designers. Its core purpose is to streamline the process of building and testing responsive, accessible, and high-performing websites. Instead of being a general-purpose browser, it’s a dedicated tool in a developer’s workflow, packed with features that address the pain points of modern web development.

The Full History of Polypane

1. Origin: A Freelancer’s Frustration (Pre-2018)

The Developer: Polypane was created by Kilian Valkhof, a well-respected web developer, consultant, and open-source contributor from the Netherlands. The project was born directly from his own experiences and frustrations as a freelancer.

The Problem: While building websites for clients, Kilian found himself constantly switching between browser windows, developer tools, and screen sizes to test responsive designs. This process was repetitive, time-consuming, and prone to error. Existing solutions involved manually resizing windows or using browser extensions that were often clunky and limited.

The “Aha!” Moment: Kilian envisioned a browser that could show multiple viewports simultaneously, allowing a developer to see how a design adapted across different screen sizes all at once. This core idea of a “poly-pane” (many panels) experience gave the browser its name.

2. Launch and Early Development (2018-2019)

Initial Release: Kilian began working on Polypane as a side project. The first public version was released around 2018.

Foundation: Unlike many alternative browsers, Polypane was built from the ground up using the Electron framework. This was a strategic choice; Electron allowed for rapid development of a cross-platform desktop application using web technologies (HTML, CSS, JavaScript). While sometimes criticized for its resource usage, it gave Kilian full control over the entire UI and feature set, which was essential for creating a unique developer tool.

Early Focus: The initial versions focused heavily on nailing the flagship feature: simultaneous viewports. It allowed developers to create panels for different screen sizes (e.g., mobile, tablet, desktop) that would all navigate and reload in sync, providing an instant, holistic view of a design’s responsiveness.

3. Growth and Feature Expansion (2020-2022)

This period marked Polypane’s transition from a clever side project to a serious, professional development tool. Kilian eventually moved to working on Polypane full-time.

Building a Comprehensive Toolset: Beyond responsive design, Polypane began integrating advanced features that developers would otherwise need multiple tools or deep DevTools knowledge to access:

Business Model: Polypane adopted a SaaS (Software as a Service) subscription model, with licenses for individuals and teams. This provided a sustainable revenue stream to support full-time development and continuous improvement.

Community Building: Kilian actively built a community around the product through a dedicated blog, Twitter presence, and participation in the web development community. The blog, in particular, became a source of high-quality articles on web development best practices, often showcasing how Polypane’s features solve real-world problems.

4. Maturity and Market Position (2023-Present)

Today, Polypane is a mature and established product in the web developer’s toolkit.

Refinement and Integration: The focus has shifted to refining existing features, improving performance, and ensuring deep integration with modern workflows (e.g., enhanced JavaScript framework debugging).

Competitive Landscape: It occupies a unique niche. While browsers like Chrome and Firefox have powerful built-in DevTools, they lack the multi-viewport, all-in-one auditing focus of Polypane. It is often compared to other developer-centric browsers like Blisk, but is generally regarded as more feature-rich, particularly in accessibility and CSS debugging.

Philosophy: Polypane’s philosophy is to “test once, see everything.” It aims to be a proactive tool that helps developers build websites correctly from the start, rather than a reactive tool used to find problems after the fact.

Key Factors in Its Success and Legacy

Scratching a Personal Itch: It solved a real, tangible problem its creator faced daily, which ensured the solution was practical and user-centric.

Niche Focus: By exclusively targeting web professionals, it avoided the impossible battle of competing with Chrome and could instead build deep, valuable features for its specific audience.

Sustainable Business Model: The subscription model allowed for dedicated, full-time development, turning a passion project into a viable business.

Credibility of the Creator: Kilian Valkhof’s established reputation in the web community gave Polypane immediate credibility and trust.

🧬 Origins and Conceptualization

2015: The idea for Polypane began when Kilian Valkhof, a web developer from the Netherlands, transitioned from using Photoshop to Sketch for web design. He sought a tool that could streamline the process of testing designs across multiple devices simultaneously. This led to the conceptualization of Polypane.

🛠️ Development and Early Prototyping

2015–2017: Kilian developed a prototype of Polypane, which he used internally at his web agency. The tool was designed to address the frustration of frequently resizing browsers to test responsive designs. As he continued to refine the prototype, he realized it significantly improved his workflow, making him up to three times faster in his development process.

🚀 Official Launch

May 16, 2017: Kilian announced Polypane to the public, inviting users to join the beta via the website Polypane.rocks.

May 14, 2019: Polypane was officially launched, marking its second anniversary with 32 releases, 18 Chromium versions, and 5 major updates.

🔧 Key Features and Evolution

Responsive Design: Polypane allows developers to view their websites across multiple devices simultaneously, facilitating efficient responsive design testing.

Built-in Tools: The browser integrates various tools for accessibility audits, SEO insights, and performance diagnostics, centralizing essential development resources. [

Regular Updates: Polypane updates approximately every month, with major versions released quarterly, incorporating new features and the latest Chromium rendering engine.

🧑‍💻 Developer’s Perspective

Kilian Valkhof: As the sole developer, designer, and support team member, Kilian emphasizes that Polypane is entirely bootstrapped, allowing him to focus solely on building the best possible browser for developers and designers.

📅 Recent Developments

October 13, 2025: Polypane 26.0.1 was released as a bugfix update.

September 29, 2025: Version 26 introduced the most accurate device emulation available, including support for small viewport units (svh) and device-specific safe area insets.

🌐 Availability

Platforms: Polypane is available for macOS, Windows, and Linux, catering to a wide range of developers.

Trial: A 14-day free trial is offered, with no credit card required, allowing users to explore its features firsthand.

In summary

Polypane represents a trend of highly specialized, premium desktop applications that cater to the nuanced needs of professionals. Its history is not one of mass-market adoption but of steadily becoming an indispensable, purpose-built tool for developers and designers who value efficiency, quality, and a streamlined workflow in building for the modern web.