How to check a WordPress plugin’s PHP version compatibility
Short answer
A plugin’s page on wordpress.org shows the oldest PHP version it needs, from the plugin’s “Requires PHP” line. That’s only a minimum. Plugins have no line for the newest PHP version they work with, so WordPress can’t warn you before a PHP upgrade that a plugin will break on it: the first sign is an error after the switch. To know whether a plugin works on PHP 8.3, 8.4 or 8.5, look at its changelog, ask its developer, or check its code for that version, which also covers custom plugins nobody else maintains.
What the plugin page tells you
On a plugin’s page on wordpress.org, the box at the side lists three versions. They come from the plugin’s own header, defined in WordPress’s plugin handbook (developer.wordpress.org). As an example, CompatNav’s own page on 16 October 2026:
| On the plugin page | What it means |
|---|---|
| WordPress version: 6.0 or higher | The oldest WordPress version it works on |
| Tested up to: 7.1.3 | The newest WordPress version the developer tested with |
| PHP version: 7.4 or higher | The oldest PHP version it needs |
The handbook defines the last one as: “Requires PHP: The minimum required PHP version.” A minimum, and nothing about the newest versions.
Why WordPress can’t warn you
WordPress reads a fixed set of plugin headers; for versions, they are “Requires at least” and “Requires PHP” (WordPress 7.1.2 source). There is no header for a highest PHP version. So:
- When your PHP is too old for a plugin, WordPress knows and says so: “This plugin does not work with your version of PHP”.
- When your PHP is too new for a plugin, WordPress has nothing to compare. No message before the upgrade; after it, a critical error or notices in the log.
The second case is the one a PHP upgrade runs into: a plugin written for PHP 7 that calls a function PHP 8 removed, a plugin that still uses something PHP 8.4 or 8.5 deprecated.
Three ways to find out
1. The changelog and support forum
On the plugin’s page, the Development tab holds the changelog, where developers often mention PHP versions: PHP 8.4 compatibility, fixed deprecation notices. The support forum shows whether others report errors on your PHP version. Useful, but only for the versions the developer chose to mention.
2. Ask the developer
Name the PHP version and the plugin version you run, for example Does version 2.3.1 run on PHP 8.4? Contacting the author has a message you can adapt. Useful when there is a developer to ask; for abandoned or custom plugins there isn’t.
3. Check the code for your PHP version
A check that reads the plugin’s code answers for the exact plugin version installed and the exact PHP version you choose, for every plugin at once, custom ones included. CompatNav is a free plugin on wordpress.org that does this on your own server for PHP 8.0 to 8.5: per plugin and theme, whether an update is available, each finding labelled “Will break” or “Deprecation notice”, the file and line, and a plain explanation.
A finding for code that a newer PHP version stops on:
What to expect
CompatNav’s page on wordpress.org says: “Well-maintained plugins often have nothing to report.” On three of the most-installed plugins together (about 7,800 PHP files), it reported 27 items for an upgrade from PHP 7.4 to 8.5, all of them deprecation notices. When something will break, look first at code that hasn’t been updated in years, and at code written for one site (custom plugins and PHP 8).
For a whole site, the same check covers the theme too (theme compatibility), and the downloadable HTML or CSV report keeps the list. Getting started shows the first scan.
Key takeaways
- “Requires PHP” is a minimum; “Tested up to” is about WordPress, not PHP.
- No plugin header states the newest PHP version a plugin supports, so WordPress shows no warning before a PHP upgrade.
- Changelogs and developers can tell you; a check of the code tells you for the exact version you choose.
- Lists of incompatible plugins go stale with every plugin release; check the versions you actually run.
- Well-maintained plugins often have nothing to report: check old and custom code first.
Frequently asked questions
Is there a list of WordPress plugins not compatible with PHP 8?
Not one that stays right: every plugin release changes the answer, and the same plugin can be fine in its current version and break in the one you run. Check the versions installed on your site, for the PHP version you’re moving to.
The plugin page says Tested up to 7.1. Does that cover PHP?
No. “Tested up to” is the newest WordPress version the developer tested with. It says nothing about PHP versions.
Can I check a plugin before installing it?
A code check reads installed files, active or not. Install the plugin without activating it, or on a staging copy, check it for your PHP version, and activate it once the answer is clear.
Check your own site before you upgrade
CompatNav is a free WordPress plugin. It reads the code of your plugins and themes on your own server and tells you, in plain words, what will break and what will only show notices on the PHP version you choose. It never changes your code. It can’t see problems that only appear while code runs with real data, so a quick check of your site after the upgrade still matters.
Sources
- developer.wordpress.org: Header Requirements
- WordPress 7.1.2 source: plugin headers (plugin.php)
- wordpress.org: CompatNav – PHP Upgrade Checker
About the code examples: each output is the real output of the code shown, run with the official PHP builds, without a php.ini, with all errors reported and displayed. Only the file path was replaced by a neutral server path.