JPEG, WebP, AVIF, or PNG: which image format should you use?
Choose an image format by content, transparency, compatibility, and editing needs—not by a blanket smallest-file rule.
The best format is the one that meets the delivery requirement at an acceptable visual quality. File size matters, but so do transparency, browser and workflow support, repeated editing, and the cost of encoding on the visitor’s device.
Start with what the image contains
Photographs contain gradients, texture, and many neighboring colors. Lossy photographic codecs can remove detail that is difficult to see and usually outperform lossless storage for this material. JPEG remains a dependable delivery format, while WebP and AVIF can produce smaller alternatives at comparable viewing quality.
Logos, interface captures, diagrams, and illustrations behave differently. Hard edges and flat color make compression artifacts easier to notice. These images may need lossless PNG or WebP, or a carefully quantized PNG that preserves the shapes and transparency while reducing the number of stored colors.
What each format is good at
JPEG is widely understood and efficient for opaque photographs, but it does not preserve transparency. WebP supports both lossy and lossless modes plus alpha transparency, making it a flexible web asset. AVIF is a high-efficiency option for photographic material, though encoding can take longer and every downstream tool should be tested before it becomes the only copy.
PNG is lossless by default and is a strong source or delivery format for graphics, text, and transparency. Its files can be large when a full-color image is stored without palette reduction. JPEG XL is available in Ziply as a local lossless Premium output, but destination support is not universal, so it should not replace a compatible master until the receiving workflow has been verified.
Choose for the destination, not just the benchmark
A website can offer a modern format while retaining a fallback through its image pipeline. A marketplace, email platform, content-management system, or print vendor may accept a narrower set. Check the actual destination before converting an entire library.
Keep the original when it is the editing master. Compression and conversion should create a delivery copy, not silently erase the source. Ziply downloads a new local file and does not replace the selected file on disk.
- Product photos: compare WebP and AVIF against the JPEG source at the intended display size.
- Logos with alpha: use PNG, lossless WebP, or a tested quantized PNG.
- Email attachments: favor formats the recipients and mail clients are known to handle.
- Archives: retain the source plus any converted delivery versions.
A reliable local comparison workflow
Run one representative image before processing a batch. Compare fine hair, foliage, text edges, gradients, and transparent boundaries at 100% zoom. Then compare the output byte size with the original. A smaller file that visibly damages the subject is not an optimization; a larger output is usually not useful unless format conversion itself was the goal.
Ziply detects the encoders available in the current browser and keeps the work on the device. Capability can differ by browser and release, so the interface—not a static compatibility promise—should be the final authority for what can be encoded in that session.