For most website graphics with transparency, save as WebP: it delivers the same see-through background at roughly a quarter to a third of the file size. Choose PNG instead when the image is a logo, icon, screenshot or line drawing with hard edges and flat color, when you need lossless pixel-perfect output, or when you still have to support very old software. Both formats are real outputs of Universal Converter, so you can convert PNG to WebP or back and compare the actual files yourself.
When to use WebP
WebP was built by Google specifically for the web, and it shows. It supports both lossy and lossless compression, an alpha channel for transparency, and animation. For photographs, gradients, soft shadows and product shots with transparent backgrounds, a lossy WebP at quality 80 typically lands 60-80% smaller than the equivalent PNG with no visible difference at normal viewing size.
Reach for WebP when:
- The graphic is a photo, hero image, or illustration with smooth gradients.
- You need transparency but the file weight matters, such as a product cut-out on a landing page.
- You are optimizing Core Web Vitals and Largest Contentful Paint, where every 100 KB counts.
- You are serving images to modern browsers. WebP is supported by every current version of Chrome, Firefox, Safari and Edge.
- You want one file to cover both transparent and non-transparent cases instead of juggling two formats.
One caveat: lossy WebP can smear thin diagonal lines and small text. If your graphic is a 40-pixel arrow icon, that softening is exactly the artifact you do not want.
When to use PNG
PNG is a lossless format, which means every pixel is stored exactly as it was authored. That makes it the better choice for anything with crisp geometry or text, and the safer choice when a file will be edited repeatedly, because lossless re-saving never compounds artifacts the way repeated lossy saves do.
Reach for PNG when:
- The image contains text, UI screenshots, charts or diagrams where edge sharpness is the whole point.
- You have flat color areas and hard-edged shapes, such as logos, icons and app assets.
- You need pixel-exact output for print preparation, mockups or design handoff.
- You are producing an image that will be opened and re-saved many times during a project.
- Compatibility is a hard requirement. PNG is supported everywhere, including in old desktop publishing tools, email clients and legacy CMS platforms where WebP may not render.
PNG also compresses flat color extremely well. A 2000-pixel-wide logo with six colors can be smaller as a PNG than as a lossy WebP, because there is almost no photographic detail for WebP's prediction model to exploit. The 'WebP is always smaller' rule breaks down exactly here.
Comparing the two formats side by side
The table above breaks down file size, transparency, compression type, animation, edge quality and browser support. The short version: WebP wins on weight for photographic content, PNG wins on fidelity for graphic content, and both handle transparency.
Why converting in the browser beats upload-based converters
Most 'convert PNG to WebP' sites work the same way: you pick a file, it travels to a server, a queue processes it, and you download the result. That model has three problems.
Privacy. Your file leaves your machine. For a client logo, an unreleased product shot, a document screenshot or anything under NDA, that is a real risk. Alvseike's converters run entirely in your browser, so the file is opened locally and never uploaded. There is no server copy to delete, because none was ever made.
Speed. A round trip to a server plus queue time is slower than converting on the hardware already in front of you, especially for large images. Local conversion starts immediately.
Watermarks and caps. Many free converters stamp output, throttle file size, or hide the uncapped version behind a subscription. Alvseike has no watermarks and no file-size caps.
What Alvseike does meter is exports: 5 runs per day without an account, 15 with a free account, and Pro at $12.99/month removes the daily limit and the per-batch file cap (free plans process up to 3 files per batch without an account, 5 with one). One plan covers all 40 Alvseike tools across images, video, audio, PDF and marketing, not just this converter. Offline use is a Pro feature. See /pricing for details.
If your graphic is a logo you want as scalable vector rather than a raster format at all, Image to SVG traces it into real vector paths locally. For framing before export, Smart Cropper crops to any ratio without uploading, and Smart Resizer hits exact pixel dimensions.
Common mistakes
Assuming WebP is always smaller. It is not. Flat-color logos and small icons often come out smaller as PNG. Always check the actual byte count on your specific file rather than trusting the general rule.
Converting a logo to lossy WebP. Lossy compression softens hard edges and can leave a faint halo around transparent shapes. If you convert a logo to WebP, use lossless mode.
Forgetting the fallback. If you still support older browsers or email clients that cannot render WebP, keep the PNG. Modern browsers are fine, but 'modern browsers' is not the same as 'everywhere my image will be pasted'.
Re-saving PNGs as JPEGs to shrink them. JPEG has no alpha channel, so your transparent background becomes a solid block. If you need smaller and transparent, WebP is the correct move, not JPEG.
Converting the same file five times. Each lossy pass degrades the image. Convert once from the original source, and export at the size you actually need rather than downscaling a converted file later.
Ignoring what the image is for. A screenshot of a dashboard should stay PNG. A photograph of the same dashboard should be WebP. The format choice follows the content, not the other way around.