Craft 5 has been the stable line since 2024. The platform improvements are substantial but for most existing sites the migration story matters more than the new features. The work breaks into stages, each with predictable UK costs and timelines for 2026.
The pre-migration audit
A migration starts with reading the site. Plugin list, custom module code, server requirements, database schema and any non-standard template patterns. The audit takes a day or so and produces a written plan covering which plugins have Craft 5 versions, which need replacing, which custom code needs rewriting and what the server upgrade path looks like.
Skipping the audit is the single most common cause of failed migrations. The plan exists to stop surprises mid-migration. Spending half a day on it saves days later.
The plugin question
Craft 5 was a major version bump and plugin maintainers had to update their work. By 2026 most actively-maintained plugins have Craft 5 versions. The ones that do not are usually abandoned plugins from authors who have moved on or have not seen the demand to update.
For each plugin in your Craft 4 site there are three possibilities. The plugin has a Craft 5 version and you upgrade. The plugin has no Craft 5 version but a working replacement exists. The plugin has no Craft 5 version and no replacement and you need to fork it or write the functionality yourself. The third case is the expensive one.
Server and database requirements
Craft 5 requires PHP 8.2 or later, MySQL 8 or PostgreSQL 13. Many Craft 4 sites still run on PHP 8.0 or 8.1 and MySQL 5.7. The server upgrade is a separate piece of work that must happen before Craft 5 will install, and it often surfaces compatibility issues with other parts of the stack.
Managed Craft hosts like Servd handle most of this transparently. Generic VPS hosting requires manual upgrade of PHP, MySQL or PostgreSQL, and verification that any other applications on the same server still work afterwards.
Deprecated APIs and custom code
Craft 5 removed APIs that were deprecated through the Craft 4 cycle. Most custom module code written for Craft 4 needs small adjustments. The Craft team published an upgrade guide that lists the breaking changes, and Craft itself ships a deprecation tracker that surfaces calls to removed APIs while the site is running.
For a site with no custom modules and only modest template-level customisation, the API changes are a non-event. For a site with a custom module that has accumulated five years of features, the rewrite work can take days.
The migration itself
The actual upgrade is straightforward. The site is staged on Craft 5, the plugin upgrades or replacements are applied, the database migrations are run, the template code is checked and the deprecation log is cleared. Most well-built Craft 4 sites complete this stage in a day or two.
Editor regression testing is the underrated part. A migration succeeds technically and then breaks for the marketing team because a plugin behaved subtly differently. Allow time for the editorial team to run through their actual workflows in the staging environment before cutover.
Realistic UK cost ranges for 2026
A clean Craft 4 site with active plugins and no major custom code: three to five working days, £2,000 to £4,000 with a UK senior freelancer.
A typical Craft 4 site with a few legacy plugins that need replacing: five to eight working days, £3,500 to £6,500.
A complex Craft 4 site with custom modules, abandoned plugins and a server upgrade required: ten to fifteen working days, £7,000 to £12,000 or more.
Craft Commerce sites cost more because the catalogue, order and customer data require additional verification. Add fifty per cent to the relevant range.
Why this work pays back
Sitting on Craft 4 is fine in the short term. Craft 4 still receives bug fixes and security patches as of 2026, though only for a limited remaining period. The longer the delay, the bigger the eventual migration because the gap to current widens and more plugins drop their Craft 4 versions.
For sites that are still on Craft 3, the migration is significantly more involved because it spans two major version jumps. If that describes your site, the audit comes first and the plan covers both steps in sequence.
For more on Craft CMS work, see Craft CMS developer UK or the Craft CMS pricing guide.
Frequently asked questions
Can we migrate Craft 4 to Craft 5 without downtime?
Almost always. The migration runs in staging, the final cutover happens during a low-traffic window with rollback procedures in place. Most sites have zero or near-zero downtime.
What is the risk of staying on Craft 4 in 2026?
Limited in the short term. Craft 4 still receives security patches. The longer the wait, the more plugins drop Craft 4 support and the wider the migration gap grows.
How long does a Craft 3 to Craft 5 migration take?
Significantly longer than Craft 4 to Craft 5. The two-step migration covers larger API changes and a larger plugin upgrade surface. Plan for two to six weeks depending on complexity.
Need to move from Craft 4 to Craft 5?
I handle Craft migrations end to end, from audit to launch, with a fixed price once the scope is clear.
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