A plugin conflict is not simply “two plugins installed together.” It is a reproducible interaction between code paths, data, hooks, requests or front-end assets. The goal is to reduce the failing combination without destroying the evidence.
Write down one reproducible failure
Define the exact action that fails: saving a post, adding to cart, submitting checkout, running cron or loading a specific admin screen. A vague report such as “the site is weird” cannot be tested consistently.
Move the test to staging when possible
Conflict isolation often requires disabling extensions. Staging protects customers and gives you freedom to repeat the same test.
Disable by groups, then narrow the group
Instead of toggling one plugin at a time across a very large stack, split non-essential plugins into groups. If the failure disappears, narrow within that group. This is faster while still preserving a logical test.
Do not forget must-use plugins and drop-ins
Standard plugin screens do not show every execution layer. MU plugins, object-cache.php, advanced-cache.php and hosting-specific integrations can remain active while normal plugins are disabled.
Check the theme and browser assets separately
A JavaScript collision can look like a PHP conflict. Likewise, a theme override may interact with a plugin template. Separate front-end asset failures from server-side execution.
Keep the minimum failing combination
Once the conflict is reproducible with the smallest set of components, inspect hooks, versions, logs and data assumptions. That is the point where a code-level fix becomes much easier.