Optimus Settings

There are various settings in Optimus that aim to help accommodate your image optimization needs and provide the best quality of image optimization. This article focusses on the Optimus settings available directly within the WordPress plugin.

Compression of thumbnail images in WordPress

In the settings of the WordPress media library, users have the option to set their own custom image sizes (preview images = thumbnails). Themes and (some) plugins additionally create their own image sizes in order to use them in the blog.

Over time, a large number of custom-set image sizes can accumulate, causing the uploading and optimization processes to slow down due to the large number of preset image sizes. In version 1.3.2 or higher, the WordPress plugin Optimus shows a list of registered image sizes that are created by WordPress and thus optimized by Optimus depending on the file size with each image upload (yes, Optimus optimizes all thumbnails of an image as well, not just the original file)

The purpose of this list: to have control over the registered image sizes/thumbnails and achieve better performance when uploading.

The transfer process when media is uploaded becomes slower the more image variants have to be created. Additionally, http://optimus.io has to optimize all of these images as well.

The question is: do all image sizes have their purpose? Maybe the theme does not use preview images and always displays the original images? If that is the case and only certain thumbnails are employed in the theme, unnecessary image size settings should be removed from the WordPress settings.

In this context we recommend the WordPress plugin “Display Registered Image Dimensions“, which lists thumbnail sizes registered by third-party applications.

Optimization of Original Images in WordPress

The function “No optimization of original images” stops Optimus from optimizing original images uploaded to WordPress. When this option is activated, the plugin only compresses preview images (=thumbnails) and always skips original images. This way, an original image uploaded to WordPress really remains untouched – untreated, but also unoptimized. Metadata, copyright information and geodata remain stored in the image.

Remove Metadata from Images

Photos that were taken using a digital camera or processed with an image editing program contain a set of meta information such as exposure time, device properties, copyright information and so on. It is recommended to remove metadata from images.

Thumbnails that are created by WordPress from uploaded pictures with available meta information also contain the metadata of the original image. This way it is ensured that the generated preview images (=thumbnails) also inherit the parameters stored in the original photo. Quite a practical feature for photographers.

In its original settings, the Optimus plugin removes all meta information from the image in order to ensure the most efficient image optimization possible. The option “No deletion of image metadata” turns off the data cleaning and keeps all the metadata stored in the image. While the gains from optimization are smaller in this case, information stored in the picture will not be lost.

Even when the option “No deletion of image metadata” is active, JPEG photos are converted to the progressive JPEG format.

Read more about how to remove metadata from images through the API: Optimus API

Convert JPEG and PNG to WebP Image Format

WebP is Google’s superior alternative image format. The key difference to photos in JPEG format is the compression method. At the same compression level, WebP image files are considerably smaller, which is a clear advantage for website performance. Read more about all the advantages and disadvantages, technical details and tools of the new image format: Convert to WebP – The Successor of JPEG

Optimus introduces WebP conversion: A WebP version is generated for each image uploaded in WordPress and optimized by Optimus. This WebP image can be displayed in supporting browsers, saving on traffic. Smart distribution of WebP files is handled by the redirection rule in .htaccess: Web server configuration to deliver WebP

WebP conversion is available to Optimus HQ customers as of Optimus 1.1.4 without additional cost. This feature can be activated in the plugin settings by navigating to your WordPress Dashboard > Settings > Optimus. Here you will see the option to select “Creation of Webp Files”.

convert jpeg png webp

WebP conversion has high resource and time requirements. Consequently, image uploads to the media library will take longer to finish. The additional conversion also puts a higher strain on the Optimus server. Therefore, this is what we recommend: Only activate WebP conversion in the plugin if you are actually using the WebP format productively. Otherwise, unnecessary strains are put on disk space and computing power.

Please note: The goal of WebP is to keep image files small and increase website load speed. Depending on the image, however, the WebP version generated can actually be larger than the source file. This is a rare occurrence, but it can happen, especially when converting PNG files.


  1. rsmith4321

    Is there a way to remove all metadata but the icc profile? I would like to preserve the color profile in the image. Thanks.

  2. Alex Kappel

    I have done all the steps including nginx setup. I can see the .webp files in uploads. But the content type served on the site is still image/jpeg even with a newly uploaded jpg. I have cleared all my cache. Is there any support for this? I am of course using Optimus HQ, and Cache Enabler activated and checked the setting as described.

  3. glenn

    Regarding this note: “Enabling this feature and re-optimizing images that you optimized before this was enabled will not convert these images to Webp. Images may only be optimized once.”

    does that mean if I ran the optimizer with the free version and then upgraded to paid and ran it again I won’t get the webp images?

    1. Cody Arsenault

      This used to be the case, however, has since changed. You can now optimize an image with the free version and then if you purchase the paid version and select the WebP option you can re-optimize the image to generate the WebP files.

  4. Øystein Thune

    Is it possible to adjust the compression of JPG’s. I think it’s too lossy (to much compression) and I want the JPG’s to be a bit better quality. If I use Tinypng.com the image is better with a bit larger files. I see that Google Pagespeed is satisfied with the compression, but I think it’s a bit too much 🙂

    1. Cody Arsenault

      It’s not possible to adjust the compression setting. This is defined based on Google PageSpeed’s recommendation.

  5. Fabi


    I have nextgen active and my pictures are not in the wordpress mediathek. is it possible to say optimus, that it should compress the images from folder X too?

    1. Cody Arsenault

      That currently isn’t possible. The images need to be available from the Media library. You could always optimize the images via the Optimus API and then upload them, although that would be a bit more time consuming.

  6. Melanie

    I’ve recently upgraded from the Free Version to Optimus HD. Now I’ve made all the settings to use WebP. Unfortunately Optimus does not optimize my pictures in this format. For testing purposes, then I uploaded a Webp file. WordPress displays it without problems. What am I doing wrong, is it because I have previously used the free version?

  7. F. Perrey

    We just bought a license for OptimiusHQ. The Bulk Optimizer as well as the Optimize function within the WP media library ignores original images, though the setting to exclude original images from optimization has been unchecked.
    What are we doing wrong!?

    Regards, FP

    1. Cody Arsenault

      Did you previously optimize your images with the free version? Also, what is the size of your original images, if they are larger than the 5MB limit, they won’t be optimized.

      1. F. Perrey

        No i don’t think they were optimized before, because they are greater than a 100KB. None of the images are greater than 5MB though. The ones I looked specifically are around 400KB to 500KB.

    1. Cody Arsenault

      This isn’t possible via the dashboard as images must be in the media library in order to be optimized and converted. You could optimize theme images manually via the API and then replace the originals with the optimized ones however I wouldn’t recommend replacing them with WebP images as Cache Enabler won’t be able to find the JPG or PNG in the event that a browser doesn’t support WebP.

  8. Guy Haines

    I started a Bulk Optimize before selecting Convert to WebP … will only new images convert to WebP or will old ones too?

    1. Cody Arsenault

      You can run the bulk optimizer again with WebP enabled and it will create the WebP images for the old images as well.

  9. Stefan


    I bought the HQ service,

    I am a bit confused here concerning the Metadata.

    Are the SEO fields for the pictures to describe the photos for SEO ranking not called Metadata?

    So in other words, if I do not keep the Metadata all my SEO work for current photos will be lost?

    Yes or No?

    1. Cody Arsenault

      Metadata typically contains lots of other unnecessary data that’s irrelevant to search engines and increases the overall size of the file. It’s recommended to remove it for both performance and security reasons. Here’s more information: https://www.keycdn.com/blog/image-metadata/

      To keep web crawlers happy you should define your image’s alt text, title, caption, etc within WordPress’s edit image feature.

  10. Adam


    Would like to find out does Optimus HQ can work WITHOUT Cache Enabler install? I am using w3tc due for cache enabler does not work with memcached…

    Seek for your kind advise.

    Thank you

    1. Cody Arsenault

      The basic JPEG or PNG compression function of Optimus will work with any caching plugin however if you need to deliver WebP images properly it is required to use Cache Enabler. This is because other caching plugins such as W3TC don’t have WebP support.

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