"All images have been optimized. Image Optimizer has saved you 0 bytes of disk space."
Are you sure you either have installed the optimizers or that you have configured TinyPNG?

Will the quality remain the same?
The optimizers are not 100% lossless, but the differences are not noticeable. We recommend using these tools for the majority of websites. In case you run a websites that for example sells images, we won't recommend it.

Will it create a backup?
No. On purpose we won't create backups. This would be cumberstome with e.g. file versions and the images in the cache directory. Instead, we overwrite the image files.

Can I exclude files?
Yes. You can add the 'Exclude from Image Optimizer' attribute to files to prevent them from being optimized.

Will it work on Windows?
The local optimizers won't work on Windows. The cloud optimizers do work on Windows.

How can I see what has happened?
There is a page "Optimized Images" that shows all the optimized images and how much space was gained. You'd also peek into the database (ImageOptimizerProcessedFiles table), or enable logging.

Can I automate image optimization?
Sure. You can execute Image Optimizer via the command line interface (CLI).
For version 2.5.0 you can use: './concrete/bin/concrete5 image-optimizer:optimize'.
For version 3.0.0 and higher you can use: './concrete/bin/concrete5 c5:job image_optimizer'.

How often does this job need to run?
Depends. On websites where lots of new images are added each day, we recommend to run the job each night. Once a file is already optimized, it will simply skip it. So performance wise there is not a reason not to run it on a regular basis.

What happens if I clear the cache?
An event will be triggered and Image Optimizer will truncate the table that holds information about which cache files have been optimized. Next time the job runs, it will optimize all images again. So yes, this is a pretty safe option.

What happens if I run the job and don't have any optimizers installed or configured?
Nothing. It will fail silently and leaves images untouched.

Can I re-run the optimizers?
Yes, you can do this without risk. It makes sense in case you hadn't installed one of the optimization tools at the time the job was run. You can do two things: 1) Go to the settings page and hit the "Clear log of processed files" button, or 2) Reinstall the add-on. This is because the add-on will remove the two tables on deinstallation.

What is the 'Clear log of processed file' button for?
It is especially useful if you have installed a new optimizer. Each time the optimizer runs, it will mark files as 'processed'. By clicking on the button it will clear the log of all the processed files, allowing you to run the optimizer again on the same files.

What is the 'Batch size' configuration setting?
The number of files the job will handle for each 'batch'. Lower this value in case the job times out. This might happen when very large images are optimized or e.g. if the max_execution_time (a PHP setting) is set too low. We'll recommend using the CLI modus though!

What happens with my "Thumbnails"?
Once a file from the Filemanager is optimized, it will 'Rescan' it. That means that its Thumbnails are regenerated.

Why doesn't this work with for example Amazon S3?
Simply because we don't have enough experience with these file storage locations to support this.

What is TinyPNG?
It's a cloud service that does optimization of JPEG and PNG images. You can obtain an API key to process 500 images per month for free. The TinyPNG service is configured to keep copyright information in the image data.

Which file types are supported?
TinyPNG supports JPEG and PNG images. If you have all local optimizers installed, JPEG, PNG, GIF, and SVG are supported.

Why are PNGs skipped in TinyPNG?
Because there is currently a bug in concrete5 that causes problems with PNG-8 bit transparent images. See also https://github.com/concrete5/concrete5/issues/3999. When this bug is fixed, we'll apply an update.