Images often make up the largest part of a web page’s size. Large, uncompressed images slow loading, waste bandwidth and hurt Core Web Vitals. Image compression tools reduce file size while keeping images looking sharp, making them one of the easiest ways to speed up a website.
Lossy vs Lossless Compression
| — | — | — |
|---|---|---|
| Lossy | Removes some data, small quality trade-off | Photos, blog images |
| Lossless | Reduces size without losing data | Logos, screenshots with text, graphics |
For most website photos, lossy compression at around 70–85% quality produces large savings with little visible difference.
Image Formats
| — | — |
|---|---|
| WebP | Smaller files for photos and graphics, broad support |
| AVIF | Excellent compression, growing support |
Types of Image Compression Tools
| — | — | — |
|---|---|---|
| Online compressors | Upload, compress, download | Occasional manual use |
| Desktop apps | Compress files locally | Batch processing, privacy |
| Image CDNs | Resize and convert automatically on delivery | Large sites, automation |
Step-by-Step Image Optimisation
- Crop to focus on the important subject
- Resize to the maximum display width (for example, 1200px for featured images)
- Choose WebP or AVIF where supported, otherwise JPEG for photos
- Compress with appropriate quality settings
- Rename files descriptively
- Add alt text after uploading
Recommended Sizes
| — | — |
|---|---|
| Blog featured image | 1200px |
| In-content image | 800–1200px |
| Thumbnails | 300–600px |
| Social sharing image | 1200×630px |
Measuring Results
Compare file sizes before and after compression and test pages in PageSpeed Insights. Look for improvements in Largest Contentful Paint and total page weight.
Common Mistakes
- Uploading photos straight from cameras or phones
- Compressing too aggressively, causing visible artefacts
- Using PNG for large photos
- Forgetting to optimise existing media library images
- Lazy-loading the main hero image
Privacy Tip
When using online compressors, avoid uploading sensitive or private images. Desktop tools process files locally.
Frequently Asked Questions
What quality setting should I use?
Around 70–85% for most photos is a good starting point; check visually.
Is WebP supported everywhere?
Most modern browsers support WebP.
Do compression plugins slow down WordPress?
They process images on upload or in the background; delivery becomes faster.
Should I compress images already uploaded?
Yes, bulk optimisation tools can process existing libraries. Back up first.
Conclusion
Image compression is one of the simplest ways to make websites faster. Resize images, choose efficient formats, apply sensible compression and automate the process. Smaller images mean faster pages, happier visitors and better performance metrics.
