Moodle Composer Vendor Directory Not Found

What the error means

Composer vendor directory not found means Moodle expected Composer-installed PHP dependencies to exist in the vendor directory, but they are missing or not readable. In Moodle 5.1 and later, this is no longer an edge-case developer problem. It can stop a normal install or upgrade.

The Moodle.org thread "error in 5.1: Composer vendor directory not found" has 57 replies, which tells you how often admins hit this while moving into the Moodle 5.x structure. Moodle also has an official Composer vendor directory not found error page for it.

The production fix is usually:

composer install --no-dev --classmap-authoritative

Run that from the Moodle root directory, not from public.

Why this happens in Moodle 5.x

Moodle 5.1 introduced Composer-managed dependencies as an explicit install check. In some 5.1 forum discussion this was described as a preparatory check rather than an immediate site-breaking condition, but by the time you are installing or upgrading Moodle 5.x, you should treat the missing vendor directory as an incomplete deployment artifact. If you use a release package that already includes the right dependencies, you may never think about Composer. If you install from Git, build your own release, upload only part of the code tree, or use a host-provided installer, the vendor directory can be missing.

The upgrade then fails because Moodle cannot load required third-party libraries.

First, check where you are running the command

Your Moodle 5.x tree has a parent Moodle directory and a public directory. Composer belongs at the parent Moodle directory.

Correct:

cd /var/www/moodle
composer install --no-dev --classmap-authoritative

Wrong:

cd /var/www/moodle/public
composer install --no-dev --classmap-authoritative

If you run Composer inside public, you are solving the wrong directory.

The safest fix for production

Use this sequence on staging first:

1. Confirm the PHP CLI version matches Moodle 5.2 requirements.
2. Go to the Moodle root directory.
3. Run Composer without dev dependencies.
4. Confirm vendor/autoload.php exists.
5. Check ownership and permissions.
6. Purge caches.
7. Run the Moodle upgrade again.

Commands:

php -v
cd /path/to/moodle
composer install --no-dev --classmap-authoritative
test -f vendor/autoload.php
php admin/cli/purge_caches.php
php admin/cli/upgrade.php

If php -v shows PHP 8.2 but your web server uses PHP 8.3 or 8.4, fix that mismatch before trusting the result. Composer can resolve platform dependencies against the wrong PHP runtime.

If you installed Moodle from Git

Git does not make dependency management disappear. After checking out the Moodle stable branch or tag, run Composer in the Moodle root.

For Moodle 5.2, a Git-based upgrade might look like:

cd /path/to/moodle
git fetch origin
git checkout -b MOODLE_502_STABLE origin/MOODLE_502_STABLE
composer install --no-dev --classmap-authoritative
php admin/cli/upgrade.php

Moodle's Git for Administrators also reminds admins to back up first and move third-party plugins into the correct 5.x locations.

If you cannot run Composer on shared hosting

This is where shared hosting gets awkward.

Some hosts do not provide shell access. Some provide shell access but no Composer. Some provide Composer, but tied to the wrong PHP version. If any of those are true, use one of these approaches:

The important rule: do not upload a half-built Moodle tree to production. The vendor directory is part of the application artifact.

For hosting-specific constraints, see Can Moodle 5.2 Run on Shared Hosting?.

If Composer itself fails

Composer failures are usually clearer than the Moodle error. Read the first actual error, not the last stack trace.

For Moodle 5.2, verify the requirements against Moodle's 5.2 release notes, then rerun Composer with the correct PHP.

Permissions after Composer

On production Linux servers, Moodle code should generally be readable by the web server but not writable by it. Moodle's upgrading guide gives the security-minded pattern of root-owned code with 755 permissions, adjusted to your server model.

After Composer creates vendor, check:

find vendor -type f -name autoload.php
ls -ld vendor
ls -l vendor/autoload.php

If the web server cannot read the directory, Moodle may still fail even though Composer ran successfully.

Do not fix this by copying random vendor folders

Copying vendor from another Moodle version is how you turn one obvious error into subtle runtime failures. The dependency tree must match the Moodle version and lock file you deployed.

Use the Moodle package for the version you are installing, or run Composer for that exact codebase.

How this connects to the Moodle 5.2 upgrade

The vendor error often appears next to other Moodle 5.x migration issues:

• The web root was not moved to public.
• Plugins were copied to old locations.
• Router configuration was skipped.
• The CLI PHP version differs from the web PHP version.
• The host's one-click installer did not match Moodle's supported process.

If more than one of those is true, step back and follow How to Upgrade Moodle 5.1 to 5.2 Safely from the beginning.

FAQ

What command fixes Composer vendor directory not found in Moodle?

Run composer install --no-dev --classmap-authoritative from the Moodle root directory. Moodle's own error page recommends that command for installing the missing dependencies.

Should the vendor directory be inside public?

No. Run Composer in the Moodle root. Do not create a separate vendor directory inside public.

Can I install Moodle 5.2 without Composer?

You can use an official Moodle release package that already includes the needed dependencies. If your deployment method does not include them, you need Composer somewhere in the build process.

Why does Composer use the wrong PHP version?

On many servers, php on the command line is not the same binary the web server uses. Check php -v, and use the host's PHP 8.3 or 8.4 CLI path if needed.

Is this a Moodle bug?

Usually no. It normally means the deployment artifact is incomplete. Treat vendor as part of the Moodle code release, not as an optional development folder.