How do I increase the WordPress memory limit when I see "Allowed memory size exhausted"?

There are two limits. WP_MEMORY_LIMIT asks WordPress to raise PHP's memory_limit, but it can only raise it up to what the server allows. Your 41943040 bytes is 40 MB, which looks like a host cap.

Set WordPress side in wp-config.php:

define( 'WP_MEMORY_LIMIT', '256M' );      // front end
define( 'WP_MAX_MEMORY_LIMIT', '512M' );  // admin, imports, image resizing

Set the PHP side (the real fix when the above is ignored). Use one that your host supports:

; php.ini or .user.ini in the site root
memory_limit = 256M

# .htaccess (Apache with mod_php only)
php_value memory_limit 256M

On PHP-FPM, edit the pool or php.ini and restart: sudo systemctl restart php8.3-fpm. On shared hosting use the control panel's PHP settings screen.

Verify: Tools > Site Health > Info > Server shows "PHP memory limit". Or wp eval 'echo ini_get("memory_limit");'.

Pitfalls

• If the value stays at 40M or 64M, the host enforces it; you need to ask support or move to a plan that allows more.
• Raising memory hides leaks. If a single page needs more than 256M, find the cause: a heavy plugin, an unpaginated query, or huge images. Query Monitor helps.
• Cloud setups with a container memory cap kill the process regardless of memory_limit.