Smaller files that still look like your photos
Graviton makes images up to 90% smaller with the open-source encoders image specialists rely on. You can compare before and after, and you get your original back if it can’t be improved.
Encoders
The engine behind every format
Each format gets the open-source encoder built for it, compiled to WebAssembly so it runs in your browser. These are the same engines used by Squoosh-style tools.
| Format | Encoder | What it does |
|---|---|---|
| JPG | MozJPEG | Mozilla’s improved JPEG encoder. It writes progressive files with optimized coding that every app, browser and printer opens. |
| WebP | libwebp | Google’s reference WebP encoder, with sharp color conversion that keeps fine colored edges clean. |
| AVIF | libavif | The widely used open-source AVIF library, for the smallest files at a given quality. It takes longer to encode large photos. |
| PNG | Palette reduction and OxiPNG | Graviton picks the best palette of up to 256 colors, with subtle Floyd–Steinberg dithering for smooth gradients. OxiPNG then optimizes how the file is stored. |
| GIF | Frame-by-frame palettes | Every frame is re-encoded with an optimized palette, storing only what changes between frames. Every frame and its timing are kept. |
| HEIC | libheif | Decodes iPhone photos so they can be saved as JPG, PNG, WebP or AVIF. |
| Resizing | High-quality resampling | The browser’s high-quality scaler, or Lanczos3 when an image is decoded in WebAssembly. Used when you resize and when you let an exact file size shrink the dimensions. |
Safeguards
Built to protect what matters in the picture
Compression always trades detail for size. Graviton is careful about where that trade lands, and shows you the result.
Compare before and after
When you compress a single image, drag the comparison slider across it to check fine detail before you download.
Never bigger than your original
If your original is already smaller than any compressed version, Graviton hands it back, pixel for pixel and without its metadata, marked Already optimal.
Smaller, not blurrier
When an exact file size would need very low quality, Graviton offers to shrink the dimensions a little instead, which looks better than heavy artifacts.
Colors that match everywhere
Colors are converted to sRGB, the standard color space for screens, so a compressed image looks the same in every browser and app.
Transparency kept
PNG, WebP and AVIF keep transparent and semi-transparent pixels. JPG has no transparency, so those areas become white.
The exact saving, every time
Each result shows its new size and how much you saved, so you can raise the quality where it matters and lower it where it doesn’t.
Choosing a quality
What the quality numbers mean
The quality slider runs from 5 to 100 and starts at 75. Graviton labels each range so you can pick by purpose.
| Quality | Label | Good for |
|---|---|---|
| 90–100 | Near lossless | Images you will edit again or print |
| 80–89 | High | Portfolio and product photos people zoom into |
| 65–79 | Balanced | Most photos for websites, email and social media (the slider starts at 75) |
| 45–64 | Small | Thumbnails and previews |
| 10–44 | Smallest | When file size matters far more than detail |
How much smaller a file gets depends on the image. A large photo straight from a phone shrinks far more than a JPG that was already compressed for the web. For screenshots and graphics, compress PNG keeps them crisp; for photos on a website, converting JPG to AVIF usually gives the smallest files. JPG vs PNG vs WebP compares the formats, and every setting, explained covers the rest of the controls. If you deliver photos to clients, see the settings for photographers.
FAQ
Image quality questions
Will people notice the compression?
At quality 75, where the slider starts, most photos look the same as the original on screen. To be sure, compare before and after, and raise the quality if you see a difference.
How much smaller will my images be?
Up to 90% smaller, depending on the image and your settings. Large photos straight from a phone or camera shrink the most; images that were already compressed shrink less. Graviton shows the exact saving for every image.
What if Graviton can’t make my image smaller?
When you keep the format and no compressed version is smaller, you get your original image back, pixel for pixel and without its metadata, marked Already optimal, rather than a bigger one.
Does Pro get better quality?
No. Both plans use the same encoders and settings. Pro only removes the daily download limit.
Why do some iPhone photos look slightly less vivid?
Graviton converts colors to sRGB so images look the same everywhere. Photos captured in a wider color space, as many iPhone photos are, can lose a little saturation in their most vivid colors.
Tools for this
Start with the format you have.
See the difference on your own photo
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