Full site editing has gone from experimental to genuinely capable, and the question of whether to migrate now comes up in almost every planning conversation we have. If you want that assessed against your actual site rather than in the abstract, that is part of what our maintenance and support work covers.
The honest answer is that migration is right for some sites and a waste of money for others. This guide sets out how to tell which one you are.
What Full Site Editing Actually Changes
In a classic theme, your templates are PHP files. Changing the header, footer, or archive layout means editing code. In a block theme, those templates are built from blocks and editable through the site editor without touching a file.
The appeal is obvious: layout changes stop requiring a developer. The cost is equally real, because your existing templates, custom fields, and theme options do not carry across automatically.
The Case for Migrating
- Layout autonomy: marketing can adjust templates without a deployment
- Alignment with core: block themes are where WordPress development effort is going
- Consistent design tokens: global styles enforce colours, spacing, and typography site-wide
- Less custom code: functionality that once needed theme options is increasingly built in
- Easier handover: a block theme is more legible to the next agency than years of bespoke PHP
The Case for Staying Put
If your current site works, converts, and is cheap to maintain, migration is a cost with no immediate return. That is not a reason to never move, but it is a reason not to move this quarter.
Sites built on ACF-driven templates deserve particular caution. Structured content entered through custom fields is easier for a non-technical editor to get right than a freeform block canvas, and moving to blocks can genuinely make editing worse rather than better.
There is a real tension here that enthusiasm for the new tooling tends to gloss over: flexibility for the person editing templates often means less guardrail for the person editing content.
Who Should Migrate, Concretely
Good Candidates
Sites due for a redesign anyway, sites whose theme is abandoned or unsupported, and sites where the marketing team is genuinely blocked waiting on developer time for layout changes. In all three cases you are paying the migration cost against work you were going to do regardless.
Poor Candidates
Sites with heavy custom functionality, WooCommerce stores with customised templates, and any site where the current setup is working and nobody is complaining. Migration for its own sake is not a strategy.
If You Do Migrate, Do It in This Order
- Inventory every custom template, field group, and theme option currently in use
- Identify what is genuinely used versus what exists but nobody touches
- Build the block theme on staging alongside the live site, not in place of it
- Rebuild templates one at a time, starting with the least commercially critical
- Migrate content structures before design, so you find data problems early
- Test editing workflows with the people who actually publish, not just developers
- Keep the classic theme installed until you are confident, so rollback stays trivial
The Hybrid Option People Forget
You do not have to choose all or nothing. A classic theme can adopt block patterns, theme.json for global styles, and the block editor for post content while keeping PHP templates. For many business sites this captures most of the benefit at a fraction of the cost.
The Bottom Line
Migrate when you have a reason beyond novelty: a redesign already scheduled, an unsupported theme, or a real bottleneck. Otherwise adopt the pieces that help and revisit the question when your next redesign comes around.
If you want an honest assessment of whether your site is a good candidate, get in touch and we will tell you plainly if the answer is no.
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