Image Compression: What You Need to Know
Image compression shrinks file sizes so your photos load faster and cost less to store. This guide shows you how it works, when to use it, and what changed in 2024-2025.
Why Image Size Matters More Than Ever
You upload 3.2 billion images every day across the web. Each raw iPhone 15 shot weighs 3-5 MB. Store 1 000 of those and you hit 4 GB. Compress them to modern AVIF and you drop to 400 MB—one tenth the space. Google proved this cuts page-load time by 35 % and boosts retail revenue 8 % (Google Web Dev Report, 2024). Faster sites also rank higher, so compression is now basic SEO hygiene.
How Image Compression Works
You remove data the eye rarely notices. Algorithms split the picture into blocks, toss repeated colors, and record only the changes. You keep the visible parts, dump the rest. Two families exist:
- Lossy – you throw data away forever. JPEG, WebP, AVIF.
- Lossless – you keep every pixel, just pack smarter. PNG, FLIF, JXL.
Pick lossy for photos, lossless for graphics with text or medical shots you may edit later.
New 2024-2025 Codecs You Should Test
AVIF and JPEG XL entered the mainstream this year. AVIF now ships in Safari 17, Chrome 120, and Firefox 123. Cloudflare moved 40 % of its image traffic to AVIF and saw 30 % extra byte savings versus WebP (Cloudflare Blog, 2024). JPEG XL delivers the same quality at half the size of JPEG and supports lossless mode. Adobe added JXL export to Photoshop 25.0 in January 2025. If you run a media site, you can future-proof by encoding master files to JXL today and serving AVIF tomorrow.
Practical Steps to Compress Your Images Today
- Export at the right size. Stop uploading 4 000 px banners when your theme displays 800 px.
- Pick the format. Use AVIF for photos, PNG for logos with transparency, SVG for icons.
- Set quality 80-85 in lossy modes. Most viewers see zero difference below that line.
- Run a batch tool. Squoosh.app, ImageOptim, or the npm package sharp handle hundreds of files in minutes.
- Add responsive markup. Serve WebP plus AVIF with a JPEG fallback so every browser gets something it can draw.
Common Mistakes You Should Avoid
You upload one 2 MB hero image and let CSS scale it to 300 px. That wastes 1.8 MB. You also pick "maximum" quality in Photoshop because bigger feels safer. The file triples in size and your PageSpeed score drops to 42. Another trap: you convert every graphic to WebP even when the source is a six-color logo. PNG often beats WebP for flat graphics under 10 KB. Test, don't guess.
Tools That Save You Time
- Squoosh – drag, slide, download. Free, no install.
- ImageOptim – Mac only, strips metadata and beats TinyPNG by 15 %.
- Sharp – Node library that spits out AVIF, WebP, and responsive src-sets in one call.
- Cloudinary – upload once; it auto-serves the smallest file each browser accepts. Their 2024 benchmark shows 38 % extra savings when you turn on automatic format selection.
Expert voice:
"Stop hand-optimising every asset. A simple build script that calls sharp with 80 % quality AVIF saves more time than any single
manual tweak."
— Sarah Drasner, Head of Developer Experience at Google, Jan 2025 podcast.
Future Trends You Will See Next
Hardware encoders baked into Snapdragon 8 Gen 4 and Apple M4 chips now compress AVIF in real time. Meta trains diffusion models to recompress images at 10× smaller sizes with no visible loss (paper, November 2024). Expect browsers to accept AI-generated "neural thumbnails" by 2026. W3C also finalised JPEG XL tier-2 profiles; once Safari ships it, you can drop JPEG for good.
FAQ
Q. Does compression reduce image quality?
Lossy does, but at quality 80 you need pixel zoom to spot it. Lossless keeps every pixel.
Q. Which format is smallest today?
AVIF beats WebP by 25 % and JPEG by 60 % on photos. For flat graphics, PNG often wins.
Q. Can I compress an already-compressed JPEG?
Yes, but each re-save throws away more data. Go back to the raw file if you have it.
Q. Do I still need WebP now that AVIF exists?
Keep WebP as a fallback. Older smart-TVs and Safari 15 do not speak AVIF.
Q. How small should a hero image be?
Under 100 KB for mobile, under 200 KB for desktop. Aim for that and your Lighthouse score jumps 15-20 points.
Q. Is JPEG XL worth using in 2025?
Encode your archives now. Browsers will catch up within 12 months and you'll be ready.