Image compression settings control how aggressively images are reduced in file size during optimization.

Use this guide to understand how compression quality, output formats, original files, and exclusions affect image optimization before changing your settings.

Image compression can reduce page weight, improve loading speed, and help performance metrics such as Largest Contentful Paint. With the Pressidium Performance Plugin, image optimization can also generate modern image formats such as WebP or AVIF, control quality level, choose which image types to optimize, and exclude images that should not be changed.

When to use this guide

Use this guide when you want to:

  • Understand image compression quality settings
  • Decide whether to prioritize smaller files or higher visual quality
  • Choose whether to keep original image files
  • Decide when to use WebP or AVIF
  • Exclude images that should not be optimized
  • Troubleshoot image quality after optimization

If you need step-by-step instructions for changing the settings in WordPress, see Image compression settings via Performance Plugin.

Access image optimization settings

To access image optimization settings:

  1. Log in to your WordPress admin dashboard.
  2. Go to Performance from the left sidebar.
  3. Open Image Optimization.
  4. Review the available compression, format, quality, and exclusion settings.

The available options may include image format selection, quality level, automatic optimization, original file handling, image editor selection, and exclusions.

How image compression works

Image compression reduces the amount of data stored in an image file.

The goal is to make images lighter while keeping acceptable visual quality. Smaller image files usually load faster and reduce the amount of data transferred to visitors.

Compression settings affect the balance between:

  • File size
  • Visual quality
  • Storage usage
  • Loading speed
  • Rollback safety

A lower quality setting usually creates smaller files, but it can make images look softer or more compressed. A higher quality setting usually preserves more detail, but the resulting files may be larger.

Compression quality

The quality setting controls how much compression is applied to optimized images.

Use a lower quality setting when:

  • Images are decorative
  • The page uses many large images
  • Speed and file size are more important than perfect detail
  • The images are not used for close visual inspection

Use a higher quality setting when:

  • Images are central to the page experience
  • The site uses photography, portfolios, product images, or visual galleries
  • Fine details, color accuracy, or sharpness matter
  • You want a more conservative optimization result

Important: Do not choose the lowest possible quality setting without testing. Over-compression can make images look blurry, banded, or visibly degraded.

WebP and AVIF output

Modern image formats can reduce file size while keeping good visual quality.

The Performance Plugin can convert images to modern formats such as WebP or AVIF, depending on your configuration and server support.

Use modern formats when you want to:

  • Reduce image transfer size
  • Improve page speed
  • Serve lighter image files to supported browsers
  • Improve performance on image-heavy pages

For a deeper explanation of modern image formats, see Image format optimization: WebP and AVIF.

Original image files

Original file handling controls whether the original image is kept after optimization.

Keeping originals gives you a safer rollback path. This is useful when you want to compare quality, restore an image, or re-optimize with different settings later.

Deleting originals can save storage, but it reduces your rollback options.

Recommended approach:

  1. Keep original images when first enabling image optimization.
  2. Test optimized images on important pages.
  3. Confirm the output quality is acceptable.
  4. Delete originals only if you are confident you no longer need them.

Important: If originals are deleted, you may not be able to restore the previous file from the plugin settings alone. Make sure you have a backup before deleting original images.

Image types to optimize

Review which image types are included before running optimization.

You may want to optimize:

  • JPEG images
  • PNG images
  • Large uploaded media files
  • Images used on key landing pages
  • Product images
  • Featured images
  • Blog post images

Be more careful with:

  • Logos
  • Icons
  • Transparent PNGs
  • Design assets
  • Images with text
  • Images that require exact color or detail

Some image types may already be small or may not benefit much from compression. Test a small set first if image quality is important.

Image editor selection

The plugin may allow you to choose the image editor used for optimization, such as Imagick or GD.

The image editor can affect format support, output quality, and compatibility with your server environment.

Use the default option unless you have a specific reason to change it.

Change the image editor only when:

  • A format is not being generated as expected
  • Image processing fails
  • Support or a developer recommends a different editor
  • Your server environment supports one editor better than the other

After changing the image editor, test a small number of images before running a large optimization job.

Exclusions

Use exclusions when specific images should not be optimized.

You may want to exclude:

  • Logos
  • Icons
  • Brand assets
  • Images with small text
  • Images that already look compressed
  • Images that require exact visual quality
  • Images used in design-critical areas
  • Images generated by another plugin or external workflow

Depending on the setting, you can exclude images using direct URLs or regular expressions.

Use the narrowest exclusion possible. Excluding one image or folder is better than disabling image optimization for the whole site.

Start with a conservative setup, then adjust based on results.

Recommended first pass:

  1. Keep original images.
  2. Enable optimization for common image types.
  3. Use a balanced quality setting.
  4. Generate WebP or AVIF if supported.
  5. Exclude logos, icons, and brand-critical assets.
  6. Optimize a small group of images first.
  7. Review output quality on key pages.
  8. Run bulk optimization only after testing.

This approach reduces risk and gives you a safer path to adjust settings later.

What to test after changing compression settings

After changing image compression settings, test pages where image quality and loading speed matter.

Check:

  • Homepage
  • Landing pages
  • Product pages
  • Blog posts
  • Portfolio pages
  • Image galleries
  • Checkout or conversion pages
  • Pages with hero images
  • Pages with logos or brand assets

Review both desktop and mobile views.

Look for:

  • Blurry images
  • Color banding
  • Loss of sharpness
  • Broken transparency
  • Missing images
  • Incorrect image dimensions
  • Images that are not being replaced by optimized versions

Common questions

Should I use the smallest possible file size?

No. Smaller files can improve performance, but image quality still matters.

Use the lowest quality setting that keeps images visually acceptable for your site.

Should I keep original images?

Yes, at least when first enabling image optimization.

Keeping originals gives you a rollback path while you test quality and compatibility.

Should I use WebP or AVIF?

Use WebP or AVIF when your site and server environment support them.

Modern formats can reduce file size, but you should still test key pages after enabling them.

Can I exclude only one image?

Yes. Use exclusions for specific images that should not be optimized.

This is better than disabling image optimization for the whole site.

Will image compression affect already optimized images?

Images that are already optimized may show smaller gains. Some files may not change much if there is little extra data to remove.

Common issues and solutions

Optimized images look blurry

The quality setting may be too low.

Increase the quality setting, keep original files, and test the image again. If the image still does not look right, exclude it from optimization.

Logos or icons look wrong

Logos, icons, and brand assets may need to stay unchanged.

Add them to the exclusion list and restore the original version if needed.

Transparent images do not look correct

Some transparent PNGs or design assets may not convert cleanly depending on the output format and settings.

Exclude the affected images or test a different format or quality setting.

Images are not being optimized

Check that image optimization is enabled and that the image type is selected.

Then open Performance > Background Processes and confirm whether optimization tasks are queued, running, paused, or completed.

For broader troubleshooting, see Images not loading.

The site still feels slow after image optimization

Image compression helps reduce image weight, but other performance issues may also affect loading speed.

Review caching, CSS and JavaScript optimization, and performance audit results. You can also run an audit from Running a performance audit.

Best practices

  • Keep original images until you verify optimized output.
  • Test a small group of images before bulk optimization.
  • Use balanced quality settings first.
  • Use WebP or AVIF when supported.
  • Exclude logos, icons, and design-critical assets.
  • Check important pages after changing settings.
  • Avoid running multiple image optimization plugins on the same files.
  • Review background processes after starting large optimization jobs.
  • Keep backups before deleting original files.

Need help?

If image compression causes quality issues or images do not optimize as expected, contact Support and include:

  • Site URL
  • WordPress version
  • Plugin version
  • Affected image URL
  • Affected page URL
  • Current compression settings
  • Selected output format
  • Selected image editor, if available
  • Whether original files were kept or deleted
  • Screenshot of the issue
  • Relevant entries from Performance > Logs, if available

Where to go next