AVIF can reduce image file sizes and may help images load sooner, but it does not guarantee faster pages, better rankings, or more revenue. The useful question is whether AVIF makes your actual images smaller at acceptable visual quality—and whether the resulting performance change improves outcomes enough to justify implementation and operating costs.
What AVIF can—and cannot—do for website performance
AVIF is an open, royalty-free image format based on AV1. It supports lossy and lossless compression, as well as wide color gamut and HDR features. Depending on the image and encoding settings, it may produce smaller files than JPEG or PNG, and sometimes WebP. There is no reliable universal savings percentage: image content, dimensions, quality settings, and the comparison format all matter. web.dev’s AVIF guidance recommends comparing compression levels and inspecting rendered output rather than assuming one setting suits every asset.
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Smaller image transfers can reduce the time needed to download an image. That may help Largest Contentful Paint (LCP) when a prominent image is the LCP element or otherwise contributes materially to page loading. It cannot, by itself, fix delays caused by server response, render-blocking resources, JavaScript, layout, or other bottlenecks. A format change is one optimization to measure, not a promise of a site-wide speed or business gain.
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What published size figures mean
In 2023, web.dev reported figures from Imgix’s AVIF announcement of 60% smaller files than JPEG and 35% smaller than WebP. Those figures describe the announcement’s reported results, not a controlled guarantee for every image set or website. In a separate 2023 exercise, web.dev reported approximately 86% median size savings against original GIFs and approximately 73% against animated JPEG XL files. That was a simple benchmark on 15 GIF samples using specified libavif/libaom and libjxl versions; it should not be generalized to all animation workloads. The article describes those limits and context.
These figures can motivate a test, but your own assets and quality requirements determine the result. Smaller bytes also do not automatically translate into a measurable LCP change if the images are not on the critical path.
Choose formats by image type and requirements
Compare formats at the visual quality acceptable for each asset, not just at a nominal encoder setting. Photographs often tolerate lossy compression better than line art, screenshots, or high-contrast text. Sharp edges and colored text on flat backgrounds can make compression artifacts especially noticeable.
| Format or approach | Where it may fit | What to evaluate |
|---|---|---|
| AVIF | Photographs or other assets where its compression and supported features suit the page. | Bytes at acceptable quality, visible artifacts, encoding and decoding cost, transparency or color requirements, and audience support. It supports lossy and lossless modes, wide color gamut, and HDR features. |
| WebP | A modern alternative worth comparing with AVIF for image delivery. | Actual bytes and appearance for the same asset and quality target; format performance can vary by content and settings. |
| JPEG | A widely used comparison or fallback for photographic assets. | Whether AVIF or WebP reduces bytes enough to warrant added delivery complexity, and whether the JPEG output remains the preferred quality or compatibility choice. |
| PNG | A comparison for assets whose image characteristics or workflow call for it. | Whether a modern format preserves required appearance and transparency while reducing transfer size. |
| SVG | Vector artwork such as suitable icons or diagrams. | Whether the content is genuinely vector artwork; it is not a like-for-like replacement for a photograph. |
| Video (for large animation) | Large animated material where video delivery is appropriate. | Playback behavior and the needs of the page. Chrome for Developers recommends considering MPEG-4 or WebM for large animations, and PNG or WebP for static images, rather than converting every GIF to AVIF. |
Historical tests also illustrate why there is no single winner across every metric. An AVIF team comparison page, updated in 2022, reported that WebP decoded faster than AVIF in tests using Chrome 110 development builds on a specified Windows laptop and a 2021 MacBook Pro. Its Kodak image set found AVIF behind WebP and JPEG XL for lossless file size. Those are dataset- and setup-specific observations, not a current or universal ranking. See the comparison’s test data and methods.
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- Choose representative pages and assets. Start with large, visible images, including hero images, and identify which actually contribute meaningful bytes or are involved in LCP. Include a range of photographs, graphics, and text-heavy images rather than testing one unusually favorable file.
- Record the baseline. For each selected asset, note its delivered format, dimensions, transfer size, and visual appearance. Record relevant page-level LCP results using a consistent measurement method and conditions.
- Make a controlled AVIF candidate. Encode the same source at suitable dimensions and several quality settings. Record output bytes and inspect the image at its actual display size for artifacts. Keep the chosen quality threshold based on what the page can accept, not on file size alone.
- Test delivery in context. Serve the candidate through the implementation you intend to maintain, including responsive selection and any CDN or cache behavior. Verify which format and dimensions the browser actually receives.
- Compare page results. Re-measure LCP and image bytes after deployment, keeping other changes as stable as practical. Chrome for Developers’ image delivery insight can help identify opportunities to avoid unnecessary image bytes.
- Evaluate the business case separately. Track relevant conversions or revenue over an appropriate period and account for other changes that might affect them. The technical result establishes whether delivery changed; it does not alone establish a commercial return.
Deploy AVIF with responsive images and safe fallbacks
Use picture sources when the browser should select a supported format
The HTML <picture> element lets you offer AVIF and WebP alternatives before a conventional fallback image. Add width-specific candidates so smaller screens need not download a large desktop file. For example:
<picture>
<source
type="image/avif"
srcset="/images/hero-640.avif 640w, /images/hero-1280.avif 1280w"
sizes="(max-width: 700px) 100vw, 1200px"
>
<source
type="image/webp"
srcset="/images/hero-640.webp 640w, /images/hero-1280.webp 1280w"
sizes="(max-width: 700px) 100vw, 1200px"
>
<img
src="/images/hero-1280.jpg"
srcset="/images/hero-640.jpg 640w, /images/hero-1280.jpg 1280w"
sizes="(max-width: 700px) 100vw, 1200px"
width="1280"
height="720"
alt="Descriptive image text"
>
</picture>Adjust candidate widths, aspect ratio, displayed size, and alternative text to match the real image and page. The browser uses supported source types and responsive information to select an image; verify the selection in browser developer tools.
Use server-side format negotiation carefully
An image server or CDN can inspect the request’s Accept header and return an appropriate format, such as AVIF, WebP, or JPEG. If the same URL can return different image formats according to Accept, return Vary: Accept so shared caches distinguish those representations. Without that variation, a cache can serve one format to a request that should receive another. More format and dimension variants also mean more cache entries and potentially more transformation or server work, so keep the candidate set purposeful.
Choose dimensions as well as format
Use srcset and sizes or an equivalent image-delivery system to offer appropriately sized candidates. A compact AVIF file can still waste bandwidth if it is far larger in pixel dimensions than the display requires. Check both the selected dimensions and the selected format on common viewport sizes.
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Choose between a self-managed pipeline and managed delivery
A self-managed workflow gives you control over encoding, quality, filenames, and deployment, but your team must produce and maintain variants, preserve fallbacks, and verify caching. An image CDN or managed image optimization service may automate responsive transformations and format negotiation. Compare options against your current hosting and CDN capabilities, cache strategy, transformation needs, operational maintenance, and service cost. Managed delivery is not automatically financially worthwhile for every site. web.dev discusses services and conversion approaches, including image CDNs and WordPress conversion plugins; confirm current features and pricing with the provider before adopting one.
AVIF and SEO: what the evidence supports
Google Search supports AVIF in Google Images and other Google Search image surfaces. Google says no special indexing action is needed solely because an image uses AVIF. If a migration changes image filenames or extensions, Google recommends server-side redirects. Its broader guidance is not to convert a site indiscriminately: evaluate which format fits the site’s needs. Google Search Central published this guidance on August 30, 2024.
AVIF may contribute to a performance improvement when it reduces bytes for images that matter to loading, but the format alone does not establish higher rankings. Treat image delivery, accessibility, discoverability, and page performance as related but distinct concerns. Preserve descriptive alternative text and ensure changed image URLs continue to resolve through redirects where needed.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Calculate site-specific ROI, not a generic payback claim
A credible ROI estimate needs both measured benefits and costs. The published compression examples establish possible byte savings under particular conditions; they do not establish a general conversion lift, revenue increase, or payback period for AVIF. Track the technical and commercial effects separately.
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1Fix the driver behind crashes, sound loss and screen glitches2Repair Windows errors before they cause bigger problems3Scan for outdated or missing drivers - takes under a minute- Asset outcome: Compare source and delivered bytes, dimensions, format, quality settings, and visual review for the actual image set.
- Performance outcome: Compare real-page LCP and relevant lab or field measurements before and after, controlling for other changes as far as practical.
- Business outcome: Measure the conversion or revenue metric that matters to the site; do not infer it from compression percentage or LCP alone.
- Costs: Include engineering and testing time, encoding or transformation costs, CDN or service charges, cache storage, and ongoing operational maintenance.
If the change saves bytes but makes little difference to relevant page metrics—or its production and maintenance costs exceed the measured benefit—it may not be worthwhile for that site. Conversely, a targeted rollout for large, important images may be more practical than converting every file.
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