How to Batch Compress Your Images With Caesium on Windows

Want to compress images nice and quick? Caesium has you covered.

Having to edit multiple images one-by-one to use them can quickly get old. Why go through each image individually to ensure it has the proper encoding, file size, or dimensions when you could automate the process? Enter Caesium.

Caesium Image Compressor is a free tool that can go through batches of images you "feed" to it and recompress them according to the specifications you define. Let's see how you can use it to simplify all your image conversions.

How to Download & Install Caesium

Since Caesium is a third-party tool, you won't find it preinstalled on your OS. So, the first step is paying a visit to Caesium's official site, downloading it, and installing it.

Note that Caesium is also available on Mac, and you can also find a command-line version of the app for Linux. There's also a new version 2.0 you can try out, but it's marked as "In Development". For this article, we'll be using the latest "stable" version on Windows 11.

Caesium comes with a user-friendly GUI, but if you don't mind typing commands, you might prefer the increased versatility of Imagemagick. For that, check our guide on how to batch edit images with Imagemagick on Windows 10.

Setting Up Caesium's Basic Configuration

Caesium Image Compressor is a straightforward app you can start using immediately. Still, it's better to first pay a visit to its settings. Some options you'll find there can help you save some more seconds and further streamline the process when batch-converting images.

For that, run Caesium and either choose Tools > Settings from its main menu. You can also click on the button with the screwdriver and wrench on its toolbar.

• On the General options page, enable Use a default output directory if none is specified and select a folder where you want Caesium to store the compressed files by default.
• We prefer (and suggest) you change the Default Image View to Fit Window instead of Original Size. This way, you'll always see complete images instead of only part of them on your screen.
• Enable Scan subdirectories when you open a folder to ensure that all image files in a folder you select will be processed, even if they're saved in folders-inside-more-folders. Enable Load the last used profile at startup to have Caesium feel as if you're "continuing from where you left a previous session" whenever you run it, instead of having to manually load a profile or set things up from scratch each time.

Move to the Compression options group. There, enable Skip if the output size is greater than the original, for what's the point in keeping a "compressed" file that ended up larger than the original?

How to Perform Batch Image Compression With Caesium

After this minimal configuration, you can begin using Caesium for converting images in batches.

Import Content

You can use the first two buttons on Caesium's toolbar to add individual pictures or a folder to its conversion list.

However, it's easier to fire up your favorite file manager, then drag and drop the files you want to convert from there on Caesium's window.

Compression Options

With the to-be-compressed content added to Caesium's list, turn your attention to the Compression Options section on the bottom-left of its window.

From there, you can set the compression quality for the produced files. The higher the quality, the larger the file sizes.

Enabling Same for all will, as it states, have Caesium use the same compression settings on all files.

If you leave this disabled, you can click on individual files on Caesium's list (use Shift or CTRL on the keyboard for multi-file selection). Then, choose a different quality and click on Set Quality to compress the selected files with your newly tweaked settings.

You can repeat the process as many times as you wish, even for each file individually, to use various compression settings for your content.

Resize Settings

Next to Compression Quality, on the bottom center of Caesium's window, you'll find the Resize settings.

As with the compression-related options, you can enable Same for all here, too. Then, choose if you want absolute or relative resizing for your files, and define the target width and height.

If you decide to Keep Aspect Ratio, the target files might not match the height value you've entered. Leave it disabled, and Caesium will also distort the images during resizing to have them match the desired target width and height.

Are you recompressing your images to reduce their size or generally "optimize them", for example, for use on a blog? Then, you might also want to enable Do not enlarge images. Doing the opposite, enlarging them, could lead to larger file sizes without a perceptible increase in quality.

Finally, remember that if you leave Same for all disabled to use different values on some files, you must click Apply with those files selected after entering new values.

Output Folder

The last step is choosing where to store the compressed files. For that, look at the Output Folder section at the bottom right of Caesium's window.

Click on the button with the three dots and choose the folder where you want Caesium to save the compressed files. The rest of the options there are self-explanatory.

You can Keep Structure to have the output files follow the same folder structure as the input files. Remember last folder will set as output the same folder you used for your previous compression. Enabling Same folder as input will save the compressed files in the same folder as the originals. Suffix allows you to add a text string after the filenames to differentiate the compressed files from the sources.

And Now, It's Time to Compress

With everything set up, click on the small Compress button on the bottom right of Caesium's file list to begin the compression process.

Caesium will show a progress bar and some additional information on the file being processed at the bottom of its window.

When the compression completes, Caesium will present a short report.

Recheck Caesium's window, turning your attention to the Ratio column. You'll see new values for each file, showing how much compression reduced their size. If some of them are red, those files ended up larger than the originals, despite being compressed. You might want to try recompressing them with different settings to reduce their size.

Note: If your files don't look good, maybe it's because they were already compressed. The best results come when using high-quality sources. Check our article on how to save high-quality images in Photoshop to learn how to preserve the quality of your source files.

How to Set Up Compression Profiles

You might be compressing images for uploading to various sites, each with a different "theme" and image size expectations. Or you might perform some other task where you find yourself dialing in the same compression settings each time. If that's the case, Caesium's support for profiles can help.

After configuring the conversion options (Compression, Resize, and Output) as you wish, choose Save Profile from the File menu.

Caesium will store your settings in a profile file for easy recall.

Profiles render compressing files for multiple "targets" trivial: just save a separate profile for each of them.

The result? The next time you need to perform a similar conversion process, it will be as easy as:

• Choosing File > Load Profile and selecting the saved profile file.
• "Dropping" the files you want to convert on Caesium's window.
• Clicking the Compress button.

Invest five minutes for Caesium's initial setup, and you'll save a multiple of that time and won't have to repeat the same tedious steps for all your future image compressions. It can't get much easier than that!

Don't Make a Salad Out Of Caesium

If you want to squish files down to size, Caesium is a great tool to have in your toolbox. Now you know how to use it and the different things it can do.