What’s the Best Format for WordPress Featured Images?

Your featured image is the face of your WordPress post. It’s the first thing people see when scrolling through your blog, and it can make or break whether someone clicks through to read your content. But here’s the thing – most WordPress users are still stuck in the stone age when it comes to image formats, blindly uploading JPEGs without a second thought.

I’ve been wrestling with WordPress images for years, and I can tell you that choosing the right format isn’t as straightforward as you might think. Sure, everyone talks about WebP these days, but is it always the best choice? Sometimes. Always? Definitely not.

Why Image Format Actually Matters

Featured images aren’t just decorative elements sitting pretty at the top of your posts. They’re workhorses. These images need to load fast, look crisp on everything from ancient mobile phones to massive 4K monitors, & still keep your page speed scores happy.

Think about it this way – your featured image is often the largest visual element above the fold. If it’s a bloated 2MB JPEG, you’ve already lost half your mobile visitors before they’ve even started reading. But compress it too much, and it looks like something from 1995.

The format you choose directly impacts three crucial things. File size, which affects loading speed. Visual quality, which affects user experience. Browser compatibility, which affects how many people can actually see your image properly.

It’s a balancing act that drives me slightly mad sometimes.

JPEG Still Has Its Place

JPEG gets a bad rap these days, especially with all the WebP evangelists running around. But here’s the truth – JPEG is still incredibly useful for featured images, particularly when you’re dealing with photographs or complex images with lots of colour variation.

The compression algorithms in JPEG are genuinely impressive. They can shrink a high resolution photograph down to a manageable size whilst maintaining decent quality. For featured images that are photographic in nature – think food blogs, travel sites, portrait photography – JPEG often performs brilliantly.

Where JPEG falls flat is with graphics, text overlays, or images with sharp edges. The compression creates artefacts that make text look fuzzy and lines appear jagged. Also, JPEG doesn’t support transparency, which can be limiting if you want your featured image to blend seamlessly with your site’s background.

File sizes with JPEG are predictable though. You can usually get a decent quality featured image down to 50-150KB without too much trouble, which isn’t terrible for loading speeds.

Plus, every browser since the dawn of time supports JPEG. Zero compatibility issues.

PNG When You Need Perfection

PNG is the perfectionist’s choice. Lossless compression means your image looks exactly as intended, with crisp edges and perfect colour reproduction. If your featured images contain text, logos, or graphics with sharp lines, PNG is often your best bet.

The transparency support is brilliant too. You can create featured images that integrate seamlessly with your site design, rather than sitting there like rectangular blocks.

But PNG files are massive. Absolutely enormous sometimes. I’ve seen PNG featured images that are 500KB or larger, which is just brutal for page loading times. Even with compression, PNG files tend to be significantly larger than their JPEG or WebP equivalents.

There’s also PNG-8 versus PNG-24 to consider, though most people don’t bother with this distinction. PNG-24 gives you full colour depth but larger files. PNG-8 limits you to 256 colours but creates smaller files.

Honestly, for most featured images, PNG is overkill unless you specifically need that transparency or crisp graphic quality.

WebP Is Usually Your Best Friend

This is where things get interesting. WebP manages to deliver JPEG-like file sizes with PNG-like quality, plus it supports transparency. It’s like someone finally created the image format we actually needed.

The compression is genuinely impressive. I’ve seen WebP images that are 30-50% smaller than equivalent JPEGs whilst looking noticeably better. For featured images, this means faster loading times without sacrificing visual appeal.

WebP also supports both lossy and lossless compression, so you can choose the approach that works best for your specific image. Photographic featured images work brilliantly with lossy WebP compression. Graphics and text overlays can use lossless compression for perfect quality.

The transparency support is excellent too, giving you the flexibility of PNG but with much smaller file sizes. Perfect for featured images that need to integrate smoothly with your site design.

Browser support has improved dramatically. Modern versions of Chrome, Firefox, Safari, and Edge all handle WebP perfectly. Even Safari finally got on board properly, though it took them long enough.

There’s just one niggling issue – older browsers still struggle with WebP, though this is becoming less of a problem as time goes on.

Getting WebP Working in WordPress

WordPress doesn’t support WebP out of the box, which is frankly ridiculous considering it’s 2024. But there are several ways to get WebP working properly for your featured images.

The easiest approach is using a plugin. ShortPixel is excellent for this – it can convert your existing images to WebP & serve them automatically to browsers that support the format. It falls back to JPEG or PNG for older browsers, so you get the best of both worlds.

Imagify is another solid choice. It handles the conversion process automatically when you upload new images, and it can bulk convert your existing featured images. The quality settings are quite granular, so you can fine tune the compression to suit your needs.

For those who prefer a more hands on approach, you can convert images to WebP before uploading. Tools like Squoosh (Google’s web based converter) work brilliantly for this. Just drag your image in, adjust the quality settings, and download the WebP version.

Some hosting providers now offer WebP conversion at the server level. Cloudflare, for instance, can automatically convert your images to WebP for compatible browsers. It’s seamless once set up properly.

The key is making sure you have fallbacks in place for browsers that don’t support WebP yet.

Sizing Your Featured Images Properly

Format choice is only half the battle. Getting the dimensions right for your featured images is equally important, and this is where many WordPress users make costly mistakes.

Most WordPress themes expect featured images to be around 1200 pixels wide. Some want 1920px for full width displays. But here’s the thing – uploading a 3000px wide image and letting WordPress scale it down is wasteful and slow.

I always resize my featured images to match what my theme actually needs. If your theme displays featured images at 1200px wide, make them 1200px wide. Don’t rely on WordPress to do the resizing for you.

The height depends on your theme’s aspect ratio requirements. Some themes want 16:9 (widescreen), others prefer 4:3 or even square formats. Check your theme documentation or just look at how existing featured images are displayed.

For retina displays, you might want to go slightly larger – maybe 1.5x the display size. So if your theme shows featured images at 800px wide, consider making them 1200px wide to look crisp on high resolution screens.

Just don’t go overboard. A 4000px featured image is almost never necessary and will slow down your site significantly.

Optimising Without Destroying Quality

Compression is where the magic happens, but it’s also where things can go horribly wrong if you’re not careful. I’ve seen too many WordPress sites with featured images that look like they’ve been compressed by a steamroller.

For JPEG featured images, I usually start around 80-85% quality and work down from there. Most images can handle 70-75% without noticeable quality loss, but photographic images with lots of detail might need higher settings.

WebP compression is more forgiving. You can often get away with lower quality settings because the compression algorithm is more sophisticated. I typically start around 75-80% for WebP and adjust based on the specific image.

Pay attention to the areas of your image that matter most. If you’re featuring a product, make sure the product itself looks crisp even if the background gets slightly compressed. Your eye will naturally focus on the main subject anyway.

Tools like TinyPNG or ShortPixel can help automate this process, but I still prefer to check each featured image manually. Automated compression sometimes makes questionable decisions, especially with images that have text overlays.

The goal is finding that sweet spot where the file size is reasonable but the quality is still excellent.

Testing & Measuring Performance

Here’s something most WordPress guides won’t tell you – you need to actually test your featured image choices. Don’t just assume that WebP is automatically better for your specific use case.

Google PageSpeed Insights will tell you how your featured images are performing. It’ll specifically call out images that are too large or poorly compressed. Pay attention to these warnings.

GTmetrix is excellent for this too. It shows you exactly which images are slowing down your page loading, and often suggests specific file size reductions for your featured images.

I also recommend testing on real devices. Your featured images might look fine on your desktop computer, but how do they perform on a smartphone with a slower connection? Sometimes the difference is eye opening.

Try converting a few of your most popular posts to WebP featured images and monitor the performance impact. You should see improvements in loading times and Core Web Vitals scores if you’ve done it properly.

Don’t forget to check how your images look across different browsers and devices though.

Final Thoughts

After years of experimenting with WordPress featured images, I’ve settled into a fairly simple approach. WebP for most situations, with JPEG as a fallback for older browsers. PNG only when I absolutely need transparency or perfect quality for graphics.

The tools have gotten so much better recently that there’s really no excuse for serving massive, unoptimised featured images anymore. Plugins like ShortPixel make the conversion process almost effortless, and the performance benefits are substantial.

That said, don’t get too caught up in the technical details. Your featured image needs to look good and load quickly, but it also needs to represent your content effectively. Sometimes a slightly larger file size is worth it if the image is significantly more compelling.

Start with WebP, test your results, and adjust based on what actually works for your specific site and audience. It’s not rocket science, but it does require some attention to detail.