For most websites, use AVIF or WebP to reduce image downloads, but keep a JPEG or PNG fallback for broad compatibility. Choose JPEG for photographs when compatibility matters, PNG for graphics that need exact edges or transparency, and WebP or AVIF when you want modern compression plus features such as transparency or animation. The best choice depends on the image, audience, and delivery path—not just its file extension.
JPEG, PNG, WebP, and AVIF at a glance
| Format | Compression | Best fit | Transparency | Animation | Progressive rendering |
|---|---|---|---|---|---|
| JPEG | Lossy | Photographs and continuous-tone still images | No alpha channel | No | Supported by progressive JPEG encodings |
| PNG | Lossless | Screenshots, diagrams, logos, text, line art, and exact edges | Full alpha transparency | No | Interlaced PNG is available |
| WebP | Lossy or lossless | Photographs and graphics where size, transparency, or animation matter | Yes | Yes | Not a general progressive-rendering choice |
| AVIF | Lossy or lossless | Bandwidth-sensitive images and modern image features | Yes | Yes | No |
JPEG remains a dependable photograph format and a useful fallback. PNG preserves image data exactly and supports transparent pixels. WebP is a practical modern option with both lossy and lossless modes. AVIF adds strong compression and features such as HDR and wide color gamut, but its browser history is shorter than JPEG or PNG’s. MDN’s format guide describes AVIF as an open, royalty-free format that carries AV1 bitstreams in the HEIF container: MDN’s image format guide.
How to choose by image type
Photographs
For a photograph without transparency, JPEG is the safe choice when you need broad compatibility or a straightforward file. For modern browsers, test WebP and AVIF versions at the quality level that looks right for your image. Use a fallback if your site serves clients whose format support you cannot assume.
Screenshots, diagrams, logos, and text
Use PNG when faithful reproduction matters: sharp text, thin lines, flat colors, and crisp boundaries can show artifacts when compressed lossily. WebP lossless or AVIF lossless may cut the download size, but compare the decoded result and file size before replacing PNG. Logos that need transparent backgrounds also require an alpha-capable format; JPEG cannot provide that transparency.
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Transparent images and composites
Use WebP or AVIF when you need transparency and want a modern, compact asset. PNG is a robust alternative when lossless compatibility is more important than minimizing bytes. For transparent photographs, inspect edges against both light and dark backgrounds; compression artifacts around semi-transparent pixels may be visible.
Animation
WebP and AVIF support animation. Choose based on the actual browsers and devices your audience uses, and test the animation in those environments. If the animation is essential and older clients are in scope, supply an appropriate fallback rather than assuming every client decodes the same format.
What file-size savings should you expect?
MDN reports that lossy WebP images are typically 25–35% smaller than visually similar JPEG images, and lossless WebP images are typically 26% smaller than equivalent PNG images. MDN also reports that lossy AVIF images are around 50% smaller than JPEG images at visually similar compression levels and generally compress better than WebP. These are typical comparisons, not guarantees for an individual asset.
Results vary with the source image, encoder, quality setting, chroma subsampling, and metadata. A simple illustration, a detailed photograph, and a screenshot can respond very differently to the same settings. Measure the files you will actually ship, and compare at a similar visual quality—not merely at matching quality-slider numbers. References: MDN and Google’s WebP documentation.
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Serve modern formats with a fallback
The HTML <picture> element lets a browser select among supplied image sources. Put preferred modern formats first, then use the <img> element as the fallback. The browser selects a source it can use; the fallback also provides the image’s alternative text and intrinsic dimensions.
<picture>
<source srcset="hero.avif" type="image/avif">
<source srcset="hero.webp" type="image/webp">
<img src="hero.jpg" alt="Descriptive alternative text" width="1200" height="800">
</picture>Use a PNG fallback instead of JPEG when the image needs transparency or exact lossless detail. Make sure each URL points to a file encoded in the declared format, and retain meaningful alternative text and dimensions. MDN documents this delivery pattern at the picture element reference.
Check support and rendering needs
Google lists native WebP support in Chrome, Safari, Firefox, Edge, and Opera, as well as in many tools and libraries. That breadth makes WebP a useful delivery format, but sites with unusual or older clients should still keep fallback content. AVIF has less historical browser depth than JPEG and PNG; confirm current support for the browsers and devices you serve rather than treating support as universal.
AVIF does not progressively render. If an image is essential to the first paint, or is large enough that gradual display matters, consider a progressive-capable fallback such as JPEG. JPEG can be encoded progressively, and PNG has an interlaced option. Progressive display is not a substitute for keeping image dimensions stable or optimizing delivery, but it can affect how a partially downloaded image appears.
Encode, test, and ship responsibly
- Keep an original. Store a high-quality source so you can regenerate variants when compression settings or delivery requirements change.
- Generate candidate files. Use an encoder appropriate to the format. Google provides the
cwebptool for converting images to WebP; see Google’s WebP documentation. - Compare at similar perceived quality. Inspect edges, texture, gradients, text, transparency, and animation. Check file size alongside visual quality.
- Implement fallbacks. Use
<picture>for format selection and verify that the fallback loads when a preferred source is unavailable. - Test actual pages. Confirm the browser requests the expected source, the image decodes, its alternative text is useful, and its dimensions do not cause avoidable layout shifts.
Performance, reliability, and cost trade-offs
Smaller image transfers can reduce bandwidth and improve loading, especially on image-heavy pages, but conversion is not automatically a win: maintaining multiple variants adds storage, build or CDN work, and opportunities for a bad source mapping. For a small site, a few carefully selected formats and fallbacks may be simpler than generating every format for every asset. For a larger site, an image CDN can negotiate formats or convert assets automatically; verify its output, caching behavior, and pricing before relying on it.
Do not choose a format solely because its extension sounds newer. A smaller file that visibly damages text or transparency is a poor trade. Also account for decoding support on the target devices and for the importance of progressive display on critical imagery.
Common image-format problems and fixes
The modern image does not appear
Check that the source URL exists, its bytes match the declared MIME type, and the browser supports that format. Keep a valid <img> fallback, and inspect the browser’s network and console panels for failed requests or decode errors.
A logo or screenshot looks blurry
The asset may have been encoded with lossy compression or resized below its display needs. Re-export from the source at the intended dimensions, use PNG or a lossless modern encoding, and check that the browser is not scaling a small raster beyond its natural size.
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Transparent edges show a halo
Inspect how the source was composited and encoded. Try PNG or a different WebP/AVIF encoder configuration, then test the result over both light and dark backgrounds. JPEG is not an option when transparency is required.
The page shows a blank image or fails to decode
Confirm the file was fully generated, the response is an image rather than an error page, and the server sends the correct content type. If the format is unsupported by a client, a working fallback is essential.
The image is larger than expected
Recheck whether the conversion preserved unnecessary metadata, whether the source dimensions exceed its rendered size, and whether the quality setting is appropriate. Compare alternate encodings using the same source and inspect the visual result before replacing the deployed asset.
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Frequently Asked Questions
Can I use AVIF without a fallback?
Only if your supported client set is known to decode it. For a broader or uncertain audience, provide a WebP, JPEG, or PNG fallback through <picture>.
Which format supports both lossless compression and transparency?
PNG, WebP, and AVIF can provide lossless images with transparency; JPEG cannot carry alpha transparency.
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