Quick answer: Moodle 5.3 removes the Classic theme from core. Sites using Classic switch to Boost during upgrade. Some settings are copied, but presets, navigation and custom SCSS may not behave the same. Treat this as a migration project rather than a theme toggle.
What Moodle migrates automatically
Brand colour, background images, login background, raw SCSS and the unneeded-blocks list can be copied into Boost. Settings left at Classic defaults do not overwrite Boost defaults. Courses, categories, users and cohorts forced to Classic return to the site theme.
What needs manual work
Classic presets and its dark-navbar setting are not copied. Blocks from the right column move into Boost’s block drawer. Custom SCSS written for Classic selectors may fail. Remove or replace $CFG->theme = 'classic' in config.php.
Three replacement paths
- Use Boost: lowest dependency risk and immediate access to the 5.3 interface.
- Install standalone Classic: useful as a temporary bridge, but it remains an additional component to maintain.
- Choose a verified Boost-derived commercial theme: suitable when branding and landing-page tools justify another dependency.
Migration checklist
Screenshot key pages, export theme settings, clone production to staging, test the switch, rebuild unsupported presets, review block placement and run accessibility checks. Keep a working fallback theme and a database backup until production validation is complete.
Choosing an alternative
AlmondB is a confirmed, free Moodle 5.3 option in Moodle Marketplace and provides a Boost-based route away from Classic. Almond Pro, Zuum, EduCard and Wellko are expected to receive 5.3 versions later but are not yet published for 5.3. Wait for the exact package rather than forcing a 5.2 release.
Related Moodle 5.3 guides
- Moodle 5.3 LTS: what is new?
- How to upgrade to Moodle 5.3
- Moodle 5.3 server requirements
- Moodle 5.3 theme compatibility checklist
Frequently asked questions
Is Classic completely unavailable?
It is no longer bundled with Moodle 5.3, but a standalone Classic package can be installed. That adds another component to maintain.
Will Moodle copy all Classic settings to Boost?
No. Several brand and SCSS settings are copied, but presets and the dark-navbar setting are not. Block placement and custom code still need review.
What happens to a config.php Classic override?
Remove or replace the classic theme setting. Leaving it in place can cause an invalid theme configuration after upgrade.
When to bring in specialist help
Use an experienced Moodle administrator or hosting engineer when the work changes database major versions, authentication, production routing, custom plugins or a heavily modified theme. Record the change, test it away from production and keep a named rollback owner.
Final recommendation
Use a staging site, rely on version-specific evidence and keep a tested rollback path. Moodle 5.3 is a strong long-term target, but a controlled upgrade is more valuable than an early upgrade that breaks teaching workflows.
Source check: Verified on 21 October 2026 against official guidance for moving from Classic to Boost and Moodle 5.3 administrator changes and free AlmondB theme.
