6 min read
How to Compress an Image Without Unnecessarily Losing Quality
Most images straight from a phone or camera are far larger than they need to be for the web, email or an upload form. A 12-megapixel photo can easily weigh 4–6 MB, while the same picture displayed on a laptop screen looks identical at a fraction of that size.
Compression is the process of storing the same picture using fewer bytes. Done carefully, nobody can tell the difference. Done carelessly, you get blocky skies, smeared text and colour banding. This guide explains where that line sits.
Lossy and lossless compression
Lossless compression (used by PNG) rearranges data more efficiently but keeps every pixel exactly. It is perfect for screenshots, logos and diagrams, but it cannot make a photograph dramatically smaller.
Lossy compression (used by JPEG and usually WebP) throws away detail the eye is unlikely to notice. The quality setting controls how aggressive that is. Because it discards information, compressing the same JPEG repeatedly makes it progressively worse — always start from the best original you have.
Which quality setting to choose
There is no universal number, but these ranges work for most photos:
- 85–92%: practically indistinguishable from the original. Good default for portfolios and product images.
- 70–80%: strong savings with minor softening visible only when zoomed in. Good for blogs and email.
- Below 60%: artefacts become noticeable, particularly around edges and in gradients such as sky.
Step by step
- Open the ToolsNest Image Compressor and add your image.
- Choose JPEG for photos without transparency, or WebP if you need transparency or the smallest size.
- Start at 80% quality and compare the previews side by side.
- Zoom in on detailed areas like hair, text or foliage. If they look fine, try lowering quality further.
- If you have a strict limit (for example 200 KB), use the target size option instead.
- Download the result and keep your original file.
When resizing beats compressing
If an image is 4000 px wide but will be displayed at 1200 px, reducing the dimensions first removes over 90% of the pixels. That usually saves more space than any quality setting, with no visible loss at the display size. Use the Image Resizer, then compress.
Limitations
Browser-based compression uses the encoders built into your browser. They are good but not as tuned as specialist desktop software, so results differ slightly between Chrome, Firefox and Safari. Re-encoding also removes metadata such as camera details and GPS location — usually a benefit for privacy, but worth knowing if you rely on that data.
In short
Start from the original, pick the right format, resize to the size you actually need, and lower quality only until you can see a difference — then step back up one notch.