Plugin inspection:

Hummingbird – Optimize Speed, Enable Cache, Minify CSS & Defer Critical JS

Use with caution

Last revised:

Confidence: Medium
This plugin has been given a short, targeted code review.

Before using this plugin, you should carefully consider these findings. Read more about this recommendation.


This recommendation applies to version 2.7.4 of this plugin, but the most recent version is 3.9.1. These findings may no longer be correct.


This is a very large plugin with multiple modular functionalities, which makes it difficult to thoroughly assess. This inspection has focused on public facing code and specifically reviewed the asset optimisation functionality. No critical issues were found. However, there are modular features that may attempt to modify server or website configuration. For example, caching and gzip compression facilities prompt to modify .htaccess files.

The user should consider possible conflicts with any existing features. For example, if caching is already in place then the plugin-specific caching facilities should not be activated. The plugin can integrate with existing services such as CloudFlare caching, but this may require configuration information that may not be readily available from hosting services.

It is therefore recommended that the features are selected carefully and tested on separate infrastructure not linked to production infrastructure, to assess the impact.

Reason for the 'Use with caution' result

The plugin has been given this recommendation at the tester's discretion:

The plugin has been rated ‘use with caution’. This is firstly due to the difficulty of fully reviewing this large code base. Secondly, by its nature the plugin may conflict with other functionalities such as other caching services or prompt for server/website configuration that should be assessed before activation.

Note that testing the asset optimisation showed it will not optimise CSS or JS assets if these are already minified and served from a CDN.

It is therefore recommended to test on safe, non-production infrastructure prior to use, and to be selective about the features used.


Failure criteria

  • Very large codebase

Read more about our failure criteria.