Compression guide
Image File Size Guide
Why image files become large
File size depends on more than the visible width and height. Camera photos, detailed backgrounds, gradients, shadows, and transparent areas can all increase the amount of data stored in the final file.
If an upload form rejects an image, the fix is usually a mix of resizing, choosing a better format, and adjusting quality.
Main factors
- Dimensions: fewer pixels usually means a smaller file.
- Format: JPG and WebP are often smaller for photos; PNG is useful for transparency and sharp graphics.
- Quality setting: lower quality can reduce JPG and WebP file size, but too much compression causes visible artifacts.
- Image detail: smooth backgrounds compress better than busy scenes.
- Transparency: PNG transparency is useful but can keep files larger.
Practical format choices
| Goal | Suggested format | Reason |
|---|---|---|
| Small website photo | WebP or JPG | Good compression for photographic detail. |
| Transparent logo | PNG | Keeps clear transparent edges. |
| Upload to an older form | JPG or PNG | Compatibility is often better than WebP. |
| Screenshot with text | PNG | Preserves sharp lines and interface text. |
Suggested workflow
- Resize the image to the largest dimensions the destination actually needs.
- Export a JPG or WebP copy for photos.
- Use PNG only when transparency or sharp text is important.
- Lower quality gradually and compare the preview before downloading.
- If the file is still too large, reduce dimensions further.
FAQ
Why did my PNG stay large?
PNG is lossless and keeps transparency. For ordinary photos, JPG or WebP is usually smaller.
Does quality affect PNG?
Browser PNG export is generally lossless, so quality sliders mainly affect JPG and WebP.
What should I try first for a rejected upload?
Resize the dimensions first. If that is not enough, choose JPG or WebP and lower quality slightly.