How to Fix 502 Bad Gateway Error in WordPress?

A 502 Bad Gateway error means your web server (Nginx or Apache) received an invalid response from PHP or an upstream service. In WordPress, this is usually caused by PHP-FPM crashes, plugin issues, memory limits, or server misconfiguration.

Step 1: Identify Your Web Server and PHP Handler

First, confirm what stack you’re using.

ps aux | grep php

Check web server:

nginx -v
apache2 -v

Most 502 issues happen with Nginx + PHP-FPM.

Step 2: Restart Web and PHP Services

This fixes temporary crashes.

For Nginx + PHP-FPM:

sudo systemctl restart php-fpm
sudo systemctl restart nginx

For Apache:

sudo systemctl restart apache2

If 502 disappears, the issue was a PHP worker crash.

Step 3: Check Server Error Logs

Logs tell the truth. Guessing doesn’t.

Nginx:

sudo tail -n 50 /var/log/nginx/error.log

Apache:

sudo tail -n 50 /var/log/apache2/error.log

PHP-FPM:

sudo tail -n 50 /var/log/php*/fpm.log

Look for:

out of memory
child exited
timeout
connection refused

Step 4: Increase PHP Memory Limit

WordPress often hits memory limits.

Edit PHP config:

sudo nano /etc/php/*/fpm/php.ini

Set:

memory_limit = 512M
max_execution_time = 300

Restart PHP-FPM:

sudo systemctl restart php-fpm

Step 5: Disable Plugins Temporarily

A broken plugin can crash PHP.

Rename plugins directory:

cd /var/www/wordpress/wp-content
mv plugins plugins-disabled

Reload the site. If 502 is gone, the issue is a plugin. Re-enable plugins one by one.

Step 6: Switch Theme to Default

Bad themes also crash PHP.

mv themes themes-disabled

WordPress will fall back to a default theme.

Step 7: Check PHP-FPM Socket Configuration (Nginx Only)

Mismatch = instant 502.

Check PHP-FPM socket:

ls /run/php/

Example:

php8.2-fpm.sock

Edit Nginx config:

sudo nano /etc/nginx/sites-enabled/your-site.conf

Ensure:

fastcgi_pass unix:/run/php/php8.2-fpm.sock;

Restart:

sudo systemctl restart php-fpm nginx

Step 8: Increase PHP-FPM Workers

Low workers = overload = 502.

Edit pool config:

sudo nano /etc/php/*/fpm/pool.d/www.conf

Adjust:

pm = dynamic
pm.max_children = 20
pm.start_servers = 5
pm.min_spare_servers = 2
pm.max_spare_servers = 10

Restart PHP-FPM:

sudo systemctl restart php-fpm

Step 9: Check Server Resources

If RAM or CPU is maxed out, nothing helps.

htop
free -h

If memory is exhausted, upgrade the server or optimize WordPress.

Step 10: Check Cloudflare or Proxy (If Used)

Cloudflare may show 502 while origin is broken.Temporarily disable proxy (orange cloud) and test directly. 502 errors are server problems, not WordPress “bugs”. If your hosting can’t handle PHP load, no plugin or theme will save you. Fix the server or expect the error to return.