Compress PNG for Games: Store Art, Uploads and Trailers

Steam wants five required capsule and screenshot sizes, all published in pixels. Smol scales an image to fit inside a pixel size and compresses it. Fit mode keeps the aspect ratio, so start from art made at the right ratio. Smol does not design the art or check Steam’s content rules, so read the page before you submit.

Steamworks’ store and library asset pages state no file-size limit, so there is no byte target to chase. That changes the job: compress for your own repository, upload time and storage, and keep the pixels exact. Screenshots are the files most worth shrinking, since a 1920 × 1080 PNG of a busy scene can be large and you need at least five.

Compress a copy, set a quality number, then look at the result at 100% zoom. Smol has no lossless mode for images: it always re-encodes, so test one file of each art style before running a folder.

On 24 small film photos saved as PNG, Smol at default settings made the files 69.2% smaller, and compressing the same PNGs to AVIF at quality 65 saved 92.1%. Those images are 768 × 512 photographs, not sprites, so treat the figures as a ceiling for photographic art and not a promise for yours. The method is on the benchmark page.

Which art compresses safely, and which does not?

• Painted backgrounds, key art and photographic screenshots take quality 75 well. Start there and zoom into gradients and skies.
• Hand-placed pixel art is the risk. Smol cannot promise pixel-identical output, so run one sprite sheet, zoom in, and keep the master if edges shift. For pixel-identical results, use a lossless tool such as the one in our ImageOptim comparison.
• UI icons with transparency: check one output on a dark and a light background before batching.
• Images that were already optimized: Smol keeps the original when compressing would make the file larger.

Set the maximum dimension to the long edge of the target and keep fit mode. Smol sets quality and pixel size, not output bytes, so check the largest output after each run.

Resize can only shrink what you give it. Starting from a 4K screenshot is better than upscaling a small one, and Smol’s upscaler (2×, 3× or 4×) is there for old art you no longer have a larger master of. For many files, compress images for web covers the same batch settings.

Work on a copy of the art folder, drop the whole folder in, and read the per-file sizes afterward. Smol writes a _compressed copy by default and leaves the original alone.

1. 1

   Copy the folder you want to shrink

   Keep the masters in your art repo or cloud storage. Never compress the only copy.

2. 2

   Drag the folder into Smol

   PNGs, JPGs, a trailer and a PDF press sheet can go in the same batch.

3. 3

   Set format, quality and maximum dimension

   Use the settings table above. Set the maximum dimension per asset type; one run produces one size.

4. 4

   Run it and check the largest output

   Open the biggest file and one with fine detail at 100%. If both look right, the batch is fine.

5. 5

   Upload the copies

   Point Steamworks or your itch.io page at the compressed files, and keep the originals for rebuilds.

For HTML5 games itch.io states 500 MB total extracted, 200 MB for any one file, and no more than 1,000 files, with paths up to 240 characters. For downloadable builds its FAQ says only that individual file size is limited, and prints no figure.

Image weight matters most in a browser build, because players download it before they play. Try WebP output for textures a web build loads, and test the running game, not only the file. For a wider look at the web side, see image optimization for web developers.

Export your trailer once at high quality, then compress a copy to MP4 with H.265 or H.264 and check the size. Smol sets quality (CRF) and resolution, not output bytes, so you may need a second run at a lower quality label.

• H.265 is Smol’s default codec, and H.264 is the alternative. The trade-offs are in H.265 vs H.264.
• A 4K capture rarely needs to stay 4K for a store page or a social post. See compressing 4K video.
• For devlog GIFs (more in README media), convert them to MP4 with GIF to MP4.
• Audio can be removed for silent loops, which also cuts size.

Steamworks’ asset pages cover images, not trailers, so check the video upload screen for the current rule. Video workflows in more depth: how to compress a video on Mac. For streamers and clip makers, see gameplay clips.

Partly. Build size is set by the texture format your engine writes at import, and an image app does not control that. Smol shrinks the source PNGs and the loose files around the build; the engine handles BC7, ASTC and the rest.

Unity’s platform texture guide lists DXT1 for RGB and BC7 or DXT5 for RGBA on desktop, ASTC for iOS, and on Android ASTC for modern GPUs with ETC2 for older ones. Those are GPU formats, chosen in the engine’s import settings, and Smol does not write them.

Where it does help: smaller source PNGs mean faster imports, a lighter repository and smaller zips of loose assets. Read compressing images before you commit them before you do, because compressed art is committed history. A Finder Quick Action makes it a right-click.

Free and built-in tools come first: your engine, a browser tool and the command line. Smol earns its $29 when you want one app for images, trailers and press PDFs without uploading anything.

The scripted option is covered in the sips command, and a side-by-side of tools is in every method compared.

Smol is a Mac app for files you already have. Five cases where something else is the answer:

• You need GPU-compressed textures (BC7, ASTC, ETC2). Those come from your engine’s import step.
• Your CI builds on Linux. Smol is not a build-time tool; use an image library in the pipeline, or the Smol API.
• You need pixel-identical output for pixel art. Smol has no lossless mode.
• You need SVG, texture atlases packed or sprite sheets generated. Smol does not write SVG or build atlases.
• You are on Windows or Linux. Smol is macOS only.