Every setting, explained
Graviton works well with its defaults, and gives you more settings when you need them: format, compression to an exact file size or a quality, crop, resize, lossless, HDR, metadata and print resolution. Here is what each one does and when to change it.
At a glance
All settings in one table
Every setting is available on both plans, including Free.
| Setting | Options | Default | Change it when |
|---|---|---|---|
| Format | Same, JPG, WebP, AVIF, PNG | Same | A site or app needs a specific format, or you want a smaller modern one |
| Compress | On or off; off keeps a JPG at about its own quality, other formats at 95 and PNGs without loss | On, and off on the crop and resize tools | You only want to crop, resize or convert |
| Goal: Exact file size | Any size in KB or MB, with presets from 10 KB to 2 MB | The preset closest to a quarter of the image’s size, or of the average for a batch | A form or website sets a maximum file size |
| Shrink dimensions if needed | On or off, with Exact file size | Off | Reaching the size needs very heavy compression, or the target can’t be met |
| Minimum size | Any size in KB, with Exact file size; JPG and PNG can be raised to it | None; set on tools for forms that have one | A form turns away files below a size, such as 20 KB |
| Goal: Quality | A slider from 5 to 100 | 75, the goal on conversion tools | You want the best balance of size and sharpness |
| Crop | Any part of one image, free or in a shape such as Square, 4:5 or 16:9; for a batch, a shape and the part each image keeps | Off | Only part of the picture matters, or it needs another shape |
| Resize | Width and height in pixels, a scale such as 50%, dragging, presets from HD to 4K and social sizes, proportions locked or not | Off | Images are larger, or smaller, than they will be shown |
| Lossless | On or off, for PNG, WebP and AVIF | Off | Every pixel must stay exactly as it is |
| Keep HDR | On or off, for JPG, HEIC and AVIF photos saved as JPG or AVIF | On | The photo is for a form or a screen that only shows standard range |
| Keep metadata | Date taken, Copyright, Camera and Location, in JPG, PNG and WebP | None: location, dates and camera details are removed; your choice is remembered on this device | Photo apps should sort by date, or your copyright should stay in the file |
| Print resolution | A DPI value for JPG and PNG, such as 200 or 300 | Not set; 200 on tools for forms that ask for it | A form gives sizes in centimetres or asks for a DPI |
In detail
What each setting does
Format
Same keeps each image’s format, so a PNG stays a PNG. iPhone HEIC photos become JPG, because browsers can read HEIC but not write it. Animated GIFs stay animated with every frame kept.
Choose JPG for photos that must open everywhere, WebP for smaller web images, AVIF for the smallest files, and PNG for screenshots, graphics and transparency. JPG has no transparency, so transparent areas become white, and converting a GIF keeps only its first frame. Format conversion covers every combination.
Compress
Compress is on everywhere but the crop and resize tools. Its goal is an Exact file size or a Quality, below.
Turn it off to only crop, resize or convert. A JPG then keeps about the quality it had, from 85 to 95, so cropping or resizing it doesn’t make the file heavier. Other formats are saved at quality 95, which looks the same as the original, and a PNG without any loss. An image you don’t crop, resize or convert comes back as your original image, pixel for pixel, without its metadata unless you keep some.
Exact file size
Exact file size is the first goal and the homepage default. The target starts at the preset closest to a quarter of the image’s size, so a 5 MB photo starts at 1 MB; for several images it uses their average size. It follows the images you add or remove until you compress them or pick a target yourself. Type a maximum in KB or MB, or pick 10 KB, 20 KB, 50 KB, 100 KB, 200 KB, 500 KB, 1 MB or 2 MB. Graviton searches for the highest quality that stays under the target. 1 KB is counted as 1,000 bytes, so the file also passes forms that count 1,024.
Shrink dimensions if needed is off by default, so your width and height stay the same and only the quality goes down. If that needs very heavy compression, or the target can’t be met, Graviton shows a note with a one-click Shrink dimensions to fit. Turn it on to let Graviton reduce the width and height a little at a time when even low quality is too big, which looks better than heavy artifacts. Read how compressing to an exact file size works for the details.
Minimum size
Some forms turn away files that are too small. With Exact file size, Add a minimum size sets a lower bound. The maximum counts kilobytes of 1,000 bytes and the minimum kilobytes of 1,024 bytes, so the file passes forms that count either way.
Graviton still keeps the highest quality under the maximum. If the image alone is below the minimum, a JPG or PNG gets a comment no viewer shows that brings the file up to it. The picture itself doesn’t change, and the result says the file was padded. Only JPG and PNG can be raised to a minimum. The exam photo compressor starts with 20–50 KB.
Quality
Switch the goal to Quality and the slider runs from 5 to 100, starting at 75. Conversion and quality tools start on this goal. Higher means a sharper image and a bigger file. A label next to the number gives a quick guide: Smallest below 45, Small from 45, Balanced from 65, High from 80 and Near lossless from 90.
For PNG and GIF, quality sets how many colors the reduced palette keeps: 256 at the top of the scale, fewer as you move toward smaller files. How Graviton keeps images sharp explains the encoders behind each format.
Crop
Tap Crop above the image, or Crop image in the settings, and drag the frame over the part to keep. Pick a shape under the image, such as Square, 4:5, 9:16 or 16:9, or Free for any shape. What you keep stays at full resolution, and the settings show its size as you drag.
For a batch, turn on Crop, pick a shape and the part each image keeps: the middle, an edge or a corner. Open an image in the list to crop it exactly. Crop and resize explains how the two work together.
Resize
Pick a size: 4K (3840 × 2160), QHD (2560 × 1440), Full HD (1920 × 1080) for full-width web images, HD (1280 × 720), Square, 1080 × 1350 and 1080 × 1920 for Instagram posts and stories, or 1200 × 630 for Facebook. Or type a width and height in pixels. With one image, tap Resize above it, then drag its corners or edges, or pick a size or a scale such as 50% under it. For a batch, turn on Resize in the settings. A cropped image is resized from its crop.
Proportions are kept unless you unlock them, so a 4000 × 3000 photo fitted to 1920 × 1920 becomes 1920 × 1440. Unlocked, or with a preset, the width and height are exact, and you choose how a photo of another shape meets them: Crop it to that shape, Add bars in white, black, a colour of your choice or transparent, or Stretch. Images in a batch that are already smaller stay as they are unless you turn on Enlarge smaller images; one image grows to any larger size you set. Enlarging goes up to 4× and 8K (33 MP), and it adds pixels but no detail. For a quick resize with these settings ready, use resize an image.
Lossless
Under More options. Lossless keeps every pixel exactly as it is for PNG, WebP and AVIF output. Files are larger than with lossy compression, so use it for screenshots, line art and images you will edit again.
Without it, PNG files are made smaller by reducing them to a palette of up to 256 colors. With it, OxiPNG only optimizes how the PNG is stored. Lossless applies to the Quality goal; Exact file size always uses lossy compression.
Keep HDR
Under More options. Many phone photos are HDR: next to the picture they carry a gain map, brightness data that makes highlights glow on HDR screens. Keep HDR re-encodes the gain map with the photo, so a JPG, HEIC or AVIF photo stays HDR as a JPG or an AVIF. It makes the file a little larger, usually by 10 to 15%.
With Exact file size the gain map gets at most 12% of the target, shrinking to fit; when it can’t fit, the photo is saved in standard range. WebP and PNG are always saved in standard range. The comparison shows both sides in standard range, so the glow only shows once you open the downloaded file on an HDR screen.
Keep metadata
Under More options. Photos carry details about themselves: when and where they were taken, the camera, and who owns them. By default every download is saved without any of it, removing EXIF (GPS location included), XMP, IPTC and comments. Only what shows the picture right stays: an original’s orientation, and an HDR photo’s brightness data. That includes an image Graviton hands back as your original: it keeps its exact pixels and loses only its metadata.
To keep some, pick Date taken, Copyright (artist and copyright), Camera (make, model, lens and exposure settings) or Location. Serial numbers, maker notes, thumbnails, XMP and IPTC are never kept. JPG, PNG and WebP carry what you keep; AVIF and GIF can’t yet. Your choice is remembered on this device. Re-encoded images also have their colors converted to sRGB. Remove metadata from photos opens with this setting first, and privacy and security explains what it means for your photos.
Print resolution
Under More options. Print resolution writes a DPI value into JPG and PNG files: how many pixels make an inch on paper. It doesn’t change the pixels.
Forms that give sizes in centimetres use it to check them. At 200 DPI, a photo 2.5 cm wide and 3.5 cm tall is 197 × 276 pixels, so set that size under Resize and 200 here. The PAN card tool does both for you.
Recipes
Settings for common jobs
Each tool below opens the compressor with these settings already chosen. You can still change any of them.
| Job | Format | Goal | Resize | Tool |
|---|---|---|---|---|
| Photos for a website | WebP | Quality 75 | 1920 px | Optimize images for your website |
| Photos to email | JPG | Quality 75 | 1600 px | Compress images for email |
| Exam or job portal photo | JPG | Exact file size, 20–50 KB | Off | Compress a photo for exam and job forms |
| Signature for a form | JPG | Exact file size, 10–20 KB | Off | Compress a signature to 10–20 KB |
| US visa photo | JPG | Exact file size, 54–240 KB | 600 × 600, cropped to a square | US visa photo resizer |
| Screenshots and graphics | Same (PNG) | Quality 80, or Lossless | Off | Compress PNG images |
| iPhone photos to share | JPG | Quality 85 | Off | HEIC to JPG converter |
| Instagram posts | JPG | Quality 90 | 1080 × 1350, cropped to 4:5 | Resize images for Instagram |
FAQ
Questions about settings
Which settings should I start with?
The defaults: Same format, the Exact file size goal, and no resize. On the homepage the target starts at the preset closest to a quarter of your image’s size, or of the average size for several images. Change the target when a form sets a different limit, switch the goal to Quality (it starts at 75) when sharpness matters more than a set size, and change the format when a site or app needs a specific one.
Does Pro unlock more settings?
No. Both plans have every setting and format. Pro only removes the daily download limit: Free includes 3 downloads a day, and Pro has no limit.
Can I change settings after compressing?
Yes. Change any setting and compress again. Compressing is unlimited and never counts against your limit, and downloading the same image again that day on the same device, in another format, size or quality, doesn’t count twice, so you can compare as many settings as you like.
Why can’t I turn on Lossless?
Lossless is available for PNG, WebP and AVIF with the Quality goal. It is off for JPG, which is always lossy, and for Exact file size, which needs lossy compression to reach a target.
Do settings apply to every image in a batch?
Yes. The settings you choose apply to every image in the batch, and each image is compressed on its own. With Exact file size, every file is brought under the same target. To crop or resize one image differently, open it in the list and give it its own.
Tools for this
Tools that start from a specific setting.
Try the settings on your own images
Try every setting free, no account needed. Both plans have them all, and Free includes 3 downloads a day.
Open the compressor