If you are an agency owner or a freelance developer, you probably have “that site” on your roster. It’s the one built five or six years ago on a classic theme. Maybe it’s heavily reliant on an older page builder, packed with technical debt, and terrifying to update.

You know you need to modernize the legacy WordPress site to take advantage of the block editor and Full Site Editing (FSE). However, the thought of a complete “rip and replace” is daunting for you. It is also expensive for your client.

On December 15th, WebDevStudios’ Brad Williams and Mitch Canter hosted a live webinar tackling this exact problem… the solution: ThemeSwitcher Pro. 

We’ve put together a recap of the key strategies and demos. These can change how you approach legacy WordPress sites moving forward.

The Problem with Legacy Sites and “Big Bang” Rebuilds

Brad kicked off the webinar by addressing the elephant in the room: legacy WordPress sites are ticking time bombs of security risks, performance issues, and maintenance nightmares.

However, the traditional solution (stopping everything to rebuild the site from scratch over six months) is flawed. These massive projects often stall and go over budget. They disrupt the client’s marketing momentum and put a significant strain on agency resources.

The alternative? A phased approach. Instead of trying to eat the elephant in one bite, you tackle modernization section by section. This keeps the live site stable the entire time.

The Solution: ThemeSwitcher Pro

The technical hurdle to a phased approach has always been WordPress’s architecture. You can only have one active theme at a time. Thus, you couldn’t efficiently run a modern block theme on the blog while keeping the legacy classic theme on the homepage.

ThemeSwitcher Pro is the solution to that architectural limitation. It allows you to conditionally load different themes on the same WordPress installation based on rules you define.

This means you can develop, test, and launch modernized sections of a live site. All this without needing complex staging environments or content freezes.

Webinar Highlights & Key Timestamps

The session was packed with strategic advice and a live walkthrough of the plugin. Here are the key moments you should jump to in the replay:

The Strategy: Why Phased Modernization Wins

• [05:01] – The Legacy Site Problem: Brad defines what makes a “legacy” site. He discusses the inherent risks of letting them sit stagnant with technical debt.
• [08:06] – The Dangers of “Rip and Replace”: Why massive rebuild projects are risky for clients and stressful for agencies.
• [08:57] – The Phased Approach Shift: The strategic pivot from thinking about modernization as a massive project to viewing it as an ongoing process.

The Demo: ThemeSwitcher Pro in Action

• [17:03] – Introducing ThemeSwitcher: Mitch introduces the tool designed to enable phased migration.
• [18:55] – The “Aha!” Moment: Mitch demonstrates the core concept. It involves running a legacy theme and a modern block theme simultaneously on the same site.
• [21:33] – Testing safely with User Conditions: How to set rules so only logged-in administrators see the new theme. Visitors still see the old site.
• [23:00] – Modernizing Section by Section: A live example of switching only specific pages (like the “About” page) or entire Post Types. Meanwhile, the rest of the site stays on the legacy theme.
• [28:18] – Scheduling Launches: Using time-based conditions to automatically switch a theme for a marketing campaign launch.

Q&A and Agency Benefits

• [32:41] – Handling Caching: Mitch addresses common questions about how theme switching interacts with server-side caching on managed hosts.
• [36:15] – Page Builders (Elementor, Divi, etc.): Confirming that ThemeSwitcher works with major page builders. This allows you to phase them out over time.
• [37:52] – The “Safety Net” for Sales: Brad explains how this tool makes it easier to sell modernization to clients. It does so by lowering the perceived risk.

Watch the Full Webinar

Moving a client from a classic monolith to a modernized WordPress site doesn’t have to be a high-stakes gamble. By adopting a phased approach, you can turn terrifying rebuilds into stable, long-term retainer work. This approach keeps your clients’ sites secure and modern.

Ready to see exactly how it works? Watch the full recording of the webinar below and download ThemeSwitcher Pro today!