If your website feels slow, images are usually the first place to look. Photos and graphics are almost always the heaviest files on a page, and shipping them as PNG or JPG often means sending far more bytes than you need to. WebP is a modern image format built to fix exactly that problem: it produces noticeably smaller files at comparable visual quality, which means faster loads for your visitors.
This guide is about converting into WebP — taking the PNG and JPG files you already have and turning them into lean, web-ready assets. It is the opposite of opening a WebP file you received; here the goal is web optimization. We will cover why WebP is smaller, how it affects page speed and Core Web Vitals, browser support and fallbacks, when each source format matters, and when WebP simply is not worth the trouble.
Why WebP files are smaller
WebP was designed for the web from the start, and it uses more advanced compression than the older formats it replaces. JPG dates back to the early 1990s and PNG to the late 1990s. WebP supports both lossy compression (like JPG) and lossless compression (like PNG), but applies smarter prediction and entropy coding in both modes. The practical result is that a WebP file usually carries the same visible detail in fewer bytes.
There is no single magic number here, and you should be suspicious of anyone who promises an exact percentage for every image. The savings depend on the content: a flat logo compresses differently than a busy photograph. But across typical website assets, WebP reliably trims file size, and smaller files are the whole point when you are trying to speed up a page.
How smaller images help page speed and Core Web Vitals
Every image on a page is a separate download. The browser has to request it, wait for it, and decode it before the visitor sees it. When those files are smaller, all of that happens faster — especially on mobile networks where bandwidth is the bottleneck.
This matters directly for Largest Contentful Paint (LCP), one of Google's Core Web Vitals. LCP measures how long it takes for the largest visible element to render, and on most pages that element is a hero image or a prominent photo. If that image is a heavy PNG, LCP suffers; if it is a compact WebP, the browser can paint it sooner. Faster LCP means a better experience for real users and a stronger signal in search rankings, which increasingly weigh page experience.
Smaller images also reduce overall bandwidth usage, lower data costs for visitors on metered connections, and ease the load on your hosting. The effect compounds on image-heavy pages like galleries, product listings, and blogs.
Browser support and fallbacks
WebP support is no longer a concern in practice. Every modern browser — Chrome, Firefox, Safari, and Edge — renders WebP today, on both desktop and mobile. For the vast majority of audiences, you can serve WebP directly.
If you still need to support very old browsers, the <picture> element makes fallbacks clean. The browser picks the first source it understands:
<picture>
<source srcset="hero.webp" type="image/webp" />
<img src="hero.jpg" alt="Description" />
</picture>
A browser that supports WebP loads hero.webp; anything older falls back to the original JPG. You get the speed benefit where it is available without breaking anyone's experience.
PNG to WebP vs JPG to WebP
The right approach depends on what you are converting. WebP handles both source types well, but for different reasons.
| Source format | Best for | Convert with | WebP benefit |
|---|---|---|---|
| PNG | Logos, icons, screenshots, graphics with transparency | Lossless WebP | Smaller files while keeping sharp edges and the alpha channel |
| JPG | Photographs and complex images | Lossy WebP | Meaningfully smaller photos at similar perceived quality |
| Existing WebP | Already optimized assets | No conversion needed | None — leave it alone |
PNG to WebP is ideal for graphics, logos, and anything with transparency. WebP supports lossless compression that preserves crisp edges and the alpha channel, so a transparent logo stays transparent and a screenshot stays pixel-accurate — just in a smaller package. Use the PNG to WebP Converter for these.
JPG to WebP shines on photographs. Photos rarely need a transparent background, so lossy WebP is the right tool: it squeezes photographic detail into fewer bytes than JPG can. Reach for the JPG to WebP Converter when your source is a photo or a screenshot saved as JPG.
When WebP is not worth it
WebP is not a universal upgrade, and forcing it everywhere wastes effort. Skip it when:
- The image is already tiny. A 2 KB icon will not get meaningfully smaller, and the conversion adds maintenance overhead for nothing.
- You need a format a specific platform demands. Some email clients, older content systems, or third-party tools still expect JPG or PNG. Print workflows almost always want the original.
- The file will be edited again. If you are mid-project and the image will be re-exported, convert at the end, not in the middle.
- You are duplicating work. If your CMS or CDN already serves WebP automatically, converting by hand is redundant.
For most public-facing website images, though, WebP is a straightforward win. And if a file is still larger than you would like after conversion, pair it with the Image Compressor to squeeze it further, or use the Image Resizer to scale oversized images down to the dimensions you actually display.
How WebP conversion works in your browser
You do not need a server, an account, or an upload to convert images to WebP. Modern browsers can do it natively. When you load an image into a <canvas> element, the browser holds the raw pixel data in memory. The canvas then exposes a toBlob() method that re-encodes those pixels into whatever format you ask for:
canvas.toBlob(
(blob) => {
// blob is now a WebP file, ready to download
},
"image/webp",
0.8 // quality, from 0 to 1
)
The second argument selects the WebP format, and the third controls quality on a scale from 0 to 1. A value around 0.8 keeps photos looking clean while still cutting file size; for lossless PNG-style conversion the encoder preserves full detail. Because every step happens on the canvas inside your browser, the image never leaves your device.
That is the privacy advantage. Your files are processed entirely on your own machine — nothing is uploaded to a server, queued in a cloud bucket, or retained anywhere. You can batch-convert an entire folder of product photos or brand assets without any of them ever crossing the network. For confidential mockups, unreleased designs, or client work under NDA, local conversion is not just convenient; it removes the risk of leaking files to a third party entirely.
How to convert PNG or JPG to WebP
- Open the PNG to WebP Converter in your browser. For photographs, use the JPG to WebP Converter instead.
- Drag in your images, or click to select them. You can add several at once for batch conversion.
- Adjust the quality setting if the tool offers one. Higher quality means larger files; lower quality means smaller files. Around 80 percent is a good starting point for photos.
- Let the conversion run. Everything happens locally in your browser, so even large batches finish quickly without an upload.
- Download your WebP files and drop them into your site, ideally inside a
<picture>element with a fallback for maximum compatibility.
The bottom line
Converting your PNG and JPG images to WebP is one of the simplest, highest-impact changes you can make for site speed. You ship fewer bytes, your largest images paint sooner, and your Core Web Vitals improve — all without sacrificing visible quality. Use lossless WebP for logos and graphics, lossy WebP for photos, keep a fallback for the rare old browser, and skip conversion only where it genuinely adds nothing. Best of all, you can do the entire job privately, right in your browser, with no files ever leaving your device.