Large image files slow down websites, fill up storage, bounce off email attachment limits and get rejected by upload forms. The good news is that most images can be made several times smaller with no difference anyone will notice. The trick is to apply the right steps in the right order.
The short version
- Resize the image to the dimensions it will actually be shown at.
- Choose the right format: JPG or WebP for photos, PNG or WebP for graphics.
- Compress with a good encoder at a sensible quality.
- Remove metadata you don’t need.
- If you have a hard limit, compress to a target size.
1. Resize first: pixels matter most
File size grows with the number of pixels. A 12-megapixel phone photo is 4000 × 3000 pixels. Shown on a website 1000 pixels wide, three quarters of the width, and fifteen sixteenths of the pixels, are wasted.
Halving the width and height keeps a quarter of the pixels, so the file typically drops to about a quarter of its size before any compression. Nothing else saves as much.
Good targets:
| Where the image is used | Long side in pixels |
|---|---|
| Blog or article image | 1200–1600 |
| Full-width website banner | 1920–2560 |
| Email or chat | 1600–2000 |
| Thumbnail | 300–600 |
| Social media post | 1080–1440 |
For high-resolution screens, aim for up to twice the size the image is displayed at, but rarely more.
2. Pick the format that fits the image
Using the wrong format is the second biggest source of bloated files.
- Photos saved as PNG are often 3–10 times larger than the same photo as JPG. Convert them.
- Screenshots and logos saved as JPG look smudged around text and may not even be smaller. Keep those as PNG.
- WebP handles both photos and graphics and is usually 25–35% smaller than JPG at the same quality, with transparency support. Every current browser shows it, so it is the best choice for your own website.
- AVIF can be smaller still, but it is slower to create and less widely accepted outside browsers.
3. Compress with a good encoder
Not all encoders are equal. The same photo saved at “80% quality” by two different programs can differ in size by 10% or more. Encoders such as MozJPEG for JPG and libwebp for WebP use extra effort to pack the data tightly.
Sensible quality settings:
- 75% for web images, email and messaging
- 80–85% for portfolios and product photos where texture matters
- 90%+ only for images you’ll print or edit later
For PNG files, quality settings don’t exist. Instead, reducing the image to a palette of 256 colours shrinks most screenshots and graphics by 60–80% without a visible change. When every pixel must stay identical, lossless optimisation still typically saves 5–50%.
4. Strip metadata
Photos carry EXIF data: camera model, settings, date, and often GPS coordinates. It usually adds a few to tens of kilobytes, and it can reveal where a photo was taken. For images you publish or share, it’s worth removing. Re-encoding an image with xconverter’s tools writes a new file from the pixels only, so metadata is left behind automatically.
5. When you have a strict size limit
Forms for applications, exams and identity checks often demand files under 20, 50 or 100 KB. Rather than guessing quality settings, use a tool that searches for the highest quality that fits. If the image still can’t fit at a reasonable quality, the dimensions need to shrink. Resize to the form’s required dimensions first if it states any; you’ll get a sharper result.
How to tell if you’ve gone too far
Compression problems show first in specific places. Zoom to 100% and check:
- Smooth areas such as skies, skin and walls for blocky patches or banding
- Edges around text and fine lines for halos and fuzz
- Gradients in graphics for visible steps in colour
- Transparent edges for jagged outlines
If you spot any of these, step the quality up by 5–10 points. A side-by-side preview makes this quick.
A worked example
A 4032 × 3024 iPhone photo converted to JPG is about 3.5 MB.
- Resized to 1600 × 1200 for a blog: about 600 KB.
- Compressed with MozJPEG at 75%: about 230 KB.
- Or converted to WebP at 75%: about 160 KB.
That is a 95% reduction, and on a laptop screen the final image looks the same as the original.
Keep your originals
Every lossy step is permanent. Keep the full-size original somewhere safe, and do all resizing and compression on copies. That way you can always produce a new version at a different size later without stacking up quality loss.