If you are using Apache or Litespeed web server below quick tutorial: How to fix Magento 2 CSS, JS, font, icon not working at frontend and backend.
First go to Magento 2 installation directory, for example in my case is /var/www/html, so
cd /var/www/html
1. Remove all static content, cache and generated folder
rm -rf pub/static var/cache var/composer_home var/generation var/page_cache var/view_preprocessed
2. Edit di.xml
File location: app/etc/di.xml
Find this Line (Word: Symlink)
<item name="view_preprocessed" xsi:type="object">Magento\Framework\App\View\Asset\MaterializationStrategy\Symlink</item>
Change to Copy
<item name="view_preprocessed" xsi:type="object">Magento\Framework\App\View\Asset\MaterializationStrategy\Copy</item>
3. Run setup upgrade
php bin/magento setup:upgrade
4. Run setup compile
php bin/magento setup:di:compile
5. Run Deploy static content command
php bin/magento setup:static-content:deploy -f
6. Flush cache
php bin/magento cache:flush
7. Reindex static block
php bin/magento indexer:reindex
8. Change permission
chmod -R 0777 var tmp pub generated
9. Replace .htaccess
Remove all .htaccess for root directory, pub directory and download .htaccess files from official Magento 2 repository (Github). Use below command:
rm -f /var/www/html/.htaccess /var/www/html/pub/.htaccess /var/www/html/pub/media/.htaccess /var/www/html/pub/static/.htaccess
Download .htaccess
For root directory
wget -O /var/www/html/.htaccess https://raw.githubusercontent.com/magento/magento2/2.4-develop/.htaccess
For pub/
wget -O /var/www/html/pub/.htaccess https://github.com/magento/magento2/raw/2.4-develop/pub/.htaccess
For pub/media
wget -O /var/www/html/pub/media/.htaccess https://github.com/magento/magento2/raw/2.4-develop/pub/media/.htaccess
For pub/static
wget -O /var/www/html/pub/static/.htaccess https://github.com/magento/magento2/raw/2.4-develop/pub/static/.htaccess
10. Fix Ownership
For example my web server is Apache – Ubuntu, the default ownership user:group is www-data:www-data, so
chown -R www-data:www-data /var/www/html/*
Solved.