Image Optimization in LiteSpeed Cache for WordPress

As of v1.6, LSCWP has the ability to optimize your images, making them smaller, and faster to transmit. For now, you will have to press a button to optimize each new batch of images, but it will be possible to configure it to be an automatic process in a later version of the plugin.

IMPORTANT: Please do NOT use other image optimization plugins alongside LSCWP's image optimization. This can cause undesirable behavior, including processing errors that require LiteSpeed staff to manually clear. Choose one image optimizer and stick with that one!

Learn more about Image Optimization on our blog.

Using the Image Optimization Page

Before You Begin

There are a few settings you may want to adjust before you request image optimization. For instance, by default we optimize your JPG/PNG images, and also create WebP versions of each image. You may choose to only create WebPs and forgo the JPG optimization.

See LSCWP Configuration Settings: Media for more information. (The Image Optimization settings can be found below those for Lazy Load.)

Optimization Summary

The first time you visit this page, you will see a button that reads Update Request Status. Press the button to obtain a key from the central server that it will use to process all of your future image optimization requests. This key isn't displayed, but it is saved as a part of your Environment Report, if we need to refer to it later for any reason.

Optimization Summary should now look like this:

You'll see there is now information displayed there: Level, Credit, Total Reduction and Last Request.

Total Reduction shows you how much space the server has saved with image optimization to date. Last Request is pretty self-explanatory.

None of the information in this section is updated automatically, so to get the most recent status you will need to press the Update Reduction Status button.

The Credit System

In an effort to prevent the Image Optimization Server from getting too bogged-down with requests, we've implemented a credit system.

Each site is assigned a level. Levels start at 1 and increase as the site continues to frequently use the service. Currently there are five established levels, and each level has an assigned number of image optimization credits (see below). Credits represent the maximum number of images you may currently submit for optimization. Credits regenerate at the completion of an optimization cycle.


Credits: 100

You submit 25 images be optimized. Credits: 75

You submit another 30 images to be optimized: Credits: 45

Your first 25 images finish processing and are pulled. Credits: 70

The next 30 images finish processing and are pulled. Credits: 100

Credits per Level
  • Level 1: 30
  • Level 2: 100
  • Level 3: 300
  • Level 4: 400
  • Level 5: 500

Image Information

Image groups total displays the number of image groups present on your site. (By “image group” we mean the collection of differently-sized images the Media Library generates when you upload a single image. Learn more here.)

Image groups not yet requested shows the number of image groups yet to be optimized.

Press Send Optimization Request and all of the unoptimized will be submitted to the central server for optimization.

Image Information should now look like this:

You'll see some changes in the status messages, and below the button you just pressed:

The bottom area of this section shows you what's happening with your current request.

  • Image groups requested: how many image groups are currently being optimized
  • Image groups failed to optimize: how many image groups were unable to be processed due to errors.
  • Image groups notified to pull: how many are complete and waiting to be pulled back into WordPress
  • Image groups optimized and pulled: how many have finished the process completely

All of this happens behind the scenes after you've pressed the Send Optimization Request button. You can refresh the page to update these numbers, and you can leave the page while optimization is running, if you've got other things to do.

When you come back to the page and the optimization is complete, Image Information should look like this:

If you have disabled the pull cron job (or your cron in general), you can press the Pull Images button to initiate the process manually. It is not necessary to press the button if your cron is running normally.

Once the images are pulled back into your media library, Image Information should look like this:

Revert Optimization

Undo Optimization

You may have decide that you no longer want optimized images on your site for whatever reason. You may use the Undo Optimization button to put everything back the way it was.

Re-do Optimization

If you change your mind again and decide you really do want the optimized images, no need to send a new request. Simply press the Re-do Optimization button, and the optimized versions will be restored.

There is no limit to the number of times you can press the above two buttons. Both versions live on your server, and may be switched in and out at will.

Send New Thumbnail Requests

Sometimes you make changes to existing images in your image library, and LSCache doesn't know about it. Use this button to re-scan your library and make LSCache aware of any images that have changed since the initial scan.

Reset IAPI Key

If your domain name has changed since you initially ran Image Optimization (as may happen when you move a deveopment site into production, for instance), then you are going to see a “hash does not match” error. To correct this problem, you'll need to press this button to generate a new IAPI key. After that, you may try again to optimize your images.

Destroy All Optimization Data

Sometimes you just want to start over from scratch. This button gives you a clean slate. It deletes the image optimization information from the database, and reverts all completed optimizations. Please note that if you have unfinished requests in progress, the credits associated with those images cannot be recovered. There is no way to undo this process, so please only press Destroy All Optimization Data if you are absolutely sure.

How it Works

You may wonder what is actually going on behind-the-scenes when images are optimized. There are two levels to this: the process that is followed when you submit a request, and the actual optimization steps that are being taken on your images.

The Process

The whole process takes place on a central web server.

  1. You press the Send Optimization Request button.
  2. The central server denies or accepts the request after callback verification.
  3. The central server distributes the task to a child server.
  4. The child server fetches your images.
  5. The child server processes your images.
  6. The child server notifies WordPress that the images are ready.
  7. A cron job runs and pulls your images back into WordPress.

Optimization Steps

What actually happens when your images are processed?

There are libraries for this sort of thing, so we don't need to reinvent the wheel. We use Imagick to adjust your images to 85%-90% quality of the original.

During the process, three versions of each image file are generated:

  • yourimage.bk.jpg: the original version of your image.
  • yourimage.jpg: the optimized version of your image, which is what will be shown on your site from now on.
  • yourimage.jpg.webp: is a version of your image saved in a format that is about 25%-34% smaller than jpg (learn more). To automatically serve WebP images to browsers that support them, just set LiteSpeed Cache > Settings > Media > Image WebP Replacement to ON.

Changing Your Mind Image by Image

If you want to revert all of your images back to the originals, use the Revert Optimization buttons above. If you decide you prefer just a single image un-optimized, you may revert it to its pre-optimization version from within the Media Library.

From the WordPress Dashboard, navigate to Media > Library. If you see an image icon in the LiteSpeed Optimization column, it means an optimized version of the image exists. If the icon is purple, then the optimized version is currently in use. If the icon is grayed-out, then the original version is in use. Click the icon to toggle between optimized and unoptimized versions.

You may also toggle the use of the WebP version using the green camera icon.


There are a number of different warning/error messages you may see after you've sent an image optimization request. Take a look at our guide to optimization errors to learn what you can do about them.

litespeed_wiki/cache/lscwp/image-optimization.txt · Last modified: 2018/01/05 16:29 by Lisa Clarke