If your site looks great but still feels heavy, it’s probably your images. In 2025 the two “next-gen” formats that matter most are WebP and AVIF. Short version: AVIF usually gives you the smallest files, but WebP is the safest fallback—and WordPress now supports both natively, so there’s no reason to stick to bloated JPEGs.
By the numbers
- WebP vs JPEG: WebP is ~25–34% smaller on average at similar quality.
- AVIF vs JPEG: AVIF files can be up to ~50% smaller than JPEG for comparable quality.
- AVIF vs WebP: Expect ~20–30% smaller AVIF files than WebP at similar quality (varies by image).
- Why it matters: On 73% of mobile pages, the LCP element is an image—shrinking image bytes directly improves Core Web Vitals.
Support in 2025
- WordPress: Upload and use WebP since WP 5.8, AVIF since WP 6.5 (server libraries like Imagick/libavif must be available).
- Browsers: AVIF and WebP are supported across all major modern browsers (Chrome, Edge, Firefox, Safari). Still keep a fallback for stragglers.
Tip: Use the HTML
<picture>element so browsers pick AVIF → WebP → JPEG automatically—no broken images, no guesswork.
Which should you pick?
Use AVIF for the smallest payload—great for hero images, product photos, and banners where every kilobyte counts. Keep WebP as your universal backup (and even JPEG as a last-ditch safety net if your stack touches older systems like email templates or legacy embeds). In practice, many teams just serve all three via <picture> and call it a day.
Real impact on Core Web Vitals
Swapping heavyweight JPEGs for AVIF/WebP is one of the fastest ways to drop LCP without redesigning anything. Combine it with responsive srcset, explicit width/height (to avoid CLS), and lazy-loading (on by default since WP 5.5), and you’ll see meaningful wins on mobile.
How to implement this on WordPress (three easy paths)
1) Plugin-based conversion (fastest to launch)
Plugins like ShortPixel, EWWW, and Imagify can generate AVIF/WebP on upload and rewrite your markup to a <picture> stack—often with responsive resizing too. Check that AVIF is toggled on.
2) CDN-based conversion (set-and-forget)
Edge services such as Cloudflare Image Resizing detect the browser’s Accept header and serve AVIF when supported, else WebP/JPEG—no template surgery required. Supported output formats explicitly include AVIF and WebP.
3) Manual export + <picture> (maximum control)
If you’re picky about art direction, export AVIF and WebP (with a JPEG fallback) and hand-craft <picture> in your theme/template. This gives you fine control over sizes/srcset and when to swap crops.
A simple <picture> you can reuse
<picture>
<source srcset="/img/hero.avif" type="image/avif">
<source srcset="/img/hero.webp" type="image/webp">
<img src="/img/hero.jpg" width="1600" height="900" alt="Hero" loading="lazy">
</picture>
This pattern lets modern browsers grab AVIF, others fall back to WebP/JPEG, and the width/height prevents layout shifts.
Rollout checklist
- Confirm support
- WordPress ≥5.8 (WebP) and ≥6.5 (AVIF).
- Hosting stack has Imagick/libavif or equivalent.
- Pick a method
- Plugin (ShortPixel / Imagify / EWWW) or CDN (Cloudflare Images/Resizing).
- Convert the heavy hitters
- Start with homepage hero, top blog posts, category/PDP templates. Measure before/after.
- Use responsive markup
srcset/sizes, explicit dimensions, and keep lazy-load on for below-the-fold media.
- Test real devices
- One modern iPhone/Android + an older iOS/Android to verify fallbacks and decode times.
- Monitor vitals
- Check PageSpeed Insights—watch LCP bytes and total image transfer.
- Bake it into workflow
- Add AVIF/WebP export presets for your content team, or leave it to the plugin/CDN rules.
Common questions
Will AVIF always beat WebP?
Mostly, yes—especially for photos and gradients. But simple graphics sometimes compress just as well (or faster to decode) with WebP. Test key assets before bulk converting. (Multiple real-world reviews show AVIF ≈ 20–30% smaller than WebP on average.)
Do I need a plugin?
No. But a good optimizer or CDN keeps your markup clean and automates fallbacks, which matters on multi-author sites.
Will this actually help rankings?
There’s no “image format ranking boost,” but faster pages improve engagement and LCP, which is a ranking signal. And because images are the LCP on most mobile pages, the gains are very real.
Want us to do it for you?
We can convert your media library to AVIF+WebP, wire up <picture> or a CDN edge rule, and ship a rollback-safe rollout in a single sprint. You’ll get a before/after Core Web Vitals report and a simple SOP your team can follow for new uploads. If that saves you a few hours (and a few headaches), ping us and we’ll send a quick plan and fixed quote—no pressure.
