Moodle 4.x vs 3.x: what mobile app compatibility actually looks like

The short answer

Quad supports Moodle 3.9 LTS through Moodle 4.5. That's six years of Moodle releases, covering the vast majority of institutional deployments in the wild. Within that range, the core APIs we use — courses, users, grades, assignments, calendar, files — have behaved consistently.

If you're on Moodle 3.9, 3.10, 3.11, 4.0, 4.1, 4.2, 4.3, 4.4, or 4.5, you're fine. If you're on Moodle 2.x or 3.0–3.8, we recommend upgrading first — Moodle's own security support has ended for those versions, and you should be moving anyway.

What changed between 3.x and 4.x

Moodle 4.0 was the first major redesign in years. The headline change was the new UI — the Boost theme got a complete overhaul. But for a mobile app, the UI doesn't matter. We don't render Moodle's web UI. We render our own UI on top of Moodle's data.

What does matter for a mobile app is the API surface. Here's what actually changed:

Course format APIs

The way Moodle represents a course's structure shifted slightly. In 3.x, the "sections and modules" model was looser — you could rely on certain field names being there. In 4.x, some of those fields became more strictly typed, and a few new ones appeared (like the "indent" property on activities). Our backend handles both shapes with a small adapter layer.

Gradebook

The gradebook API saw the biggest changes. Moodle 4.0 introduced grade improvements that affected how letter grades and weighted averages are computed. If you're using complex grade categories with conditional formulas, the output structure differs between 3.x and 4.x.

For most institutions, this doesn't matter — Moodle reports the same final grade either way. For institutions with bespoke grade calculation logic, we sometimes need to test against your specific Moodle to make sure the mobile app shows the same grade your faculty are looking at.

Calendar and events

Moodle 4.0 unified the calendar system. In 3.x, course events, user events, group events, and site events were retrieved through different endpoints. In 4.x, there's one consistent calendar API. Our backend handles both — but it means we maintain two code paths, and the 3.x path is slightly slower because of the extra round-trips.

Plugins compatibility

This is the place to be careful. Moodle plugins from the 3.x era don't all work on 4.x. The flip side is also true: plugins built for 4.x sometimes don't run on 3.x. If you've installed a plugin we haven't seen before, we need to check it during discovery.

The stuff that didn't change

The core student experience APIs — login, enrolment, course content, assignment submission, file uploads — have been stable across all supported versions. If you can pull a list of a student's courses from your Moodle today, we can show those courses on a phone.

SSO has also been stable. OAuth 2.0, SAML 2.0, LDAP, and Moodle-native auth all work the same way across 3.x and 4.x. We've never had a deployment fail because of SSO incompatibility.

The Moodle 4.1 LTS sweet spot

If you're on Moodle 4.1 LTS, you're in the best possible place. It's the long-term support release, will be supported by Moodle HQ until late 2026, has all the API improvements from 4.0, and has had enough time in production to be solid.

For institutions about to do a Moodle upgrade, we usually recommend going to 4.1 LTS rather than the bleeding edge of 4.x. Newer 4.3, 4.4, 4.5 releases have more features but also more change-velocity. LTS is the conservative choice.

If you don't know what version you're on

Don't worry — many institutions don't. To check: log into your Moodle as an admin, go to Site Administration → Notifications. The Moodle version will be displayed at the top. If you can't get to that screen, ask your Moodle administrator or hosting provider.

Alternatively: send us your Moodle URL and we'll check non-invasively via the public version endpoint. No login required.

The bottom line

Don't let Moodle version concerns delay a mobile app project. Almost certainly, your Moodle is supported. The few cases where it isn't, the answer is usually "upgrade Moodle first" — something you probably should be doing anyway for security reasons.