There is no single best web image format. Use JPEG (JPG) for broadly compatible photographs, PNG when transparency or exact pixel reproduction matters, SVG for scalable icons and diagrams, and WebP or AVIF when modern compression is supported by your audience. Serve newer formats with a conventional fallback, then compare real files at acceptable quality before changing an entire site.
Choose the format by image content first
Format selection starts with what the image contains, not with a universal compression ranking. A photograph, a flat-color logo and an animated illustration have different requirements.
JPEG/JPG for ordinary photographs
JPEG is a widely supported, lossy format for still photographs. Its compression discards information, so repeated editing and re-saving can create visible artifacts. It is a practical fallback when maximum compatibility matters. For photographs, also test WebP and AVIF versions at the quality level your pages can accept.
PNG for transparency and precise reproduction
PNG is useful when an alpha channel (transparent pixels) or more exact reproduction of source artwork is important. Screenshots, interface captures, text-heavy graphics and logos can show compression artifacts in JPEG. PNG files are often larger than newer alternatives, so compare a PNG with WebP or AVIF when your delivery stack supports them.
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SVG for vectors
SVG is a vector format rather than a raster format. Icons, interface elements, charts and diagrams can remain crisp at different sizes because the browser renders paths instead of enlarging a fixed pixel grid. Use a normal <img> element when you want the asset indexed as an image; Google does not index CSS background images as image content. SVG is listed among the image formats Google Search supports.
WebP for a practical modern default
WebP supports lossy and lossless compression, transparency and animation. MDN notes that WebP has broader browser support than AVIF and supports progressive rendering. It is a strong candidate for photos and transparent graphics when your audience supports it, but file size and visual quality still depend on the source and encoder settings.
AVIF when compression or advanced color features matter
AVIF supports still and animated images, transparency and higher color depth. It can compress slightly better than WebP in some cases, according to MDN, but support and decoding behavior should be checked for your actual audience. Serve a fallback if clients that cannot decode AVIF are important to you.
GIF, APNG and JPEG XL
- GIF: suitable for basic imagery or simple animation where legacy compatibility is the priority. For new animation, MDN suggests considering WebP, AVIF or APNG; for lossless indexed stills, PNG is generally preferable.
- APNG: provides lossless animation. WebP and AVIF may perform better, while support varies by audience.
- JPEG XL: offers features such as progressive decoding, HDR, wide color gamut, transparency and animation, but MDN reports that browser support is not universal. Use a
<picture>fallback when experimenting with it.
What the published compression numbers really mean
Google’s 2025 WebP documentation reports WebP lossless files averaging 26% smaller than PNG, and lossy WebP files 25–34% smaller than comparable JPEG at equivalent SSIM quality. These are Google’s published comparisons, not a guarantee for every image. Your result changes with image dimensions, texture, transparency, encoder and quality setting. Measure representative assets rather than applying the percentages to a budget or performance claim.
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Use picture with an img fallback
The safest way to offer modern alternatives is to list preferred sources first and retain a normal img with src. Google recommends always specifying a fallback URL because some browsers or crawlers may not understand picture or srcset.
<picture>
<source type="image/avif" srcset="image.avif">
<source type="image/webp" srcset="image.webp">
<img src="image.jpg" alt="Descriptive alternative text" width="1200" height="800">
</picture>The browser chooses the first source it can use. Add density or width variants when you actually generate matching files:
<picture>
<source type="image/avif" srcset="photo-800.avif 800w, photo-1600.avif 1600w" sizes="(max-width: 800px) 100vw, 800px">
<source type="image/webp" srcset="photo-800.webp 800w, photo-1600.webp 1600w" sizes="(max-width: 800px) 100vw, 800px">
<img src="photo-800.jpg" srcset="photo-800.jpg 800w, photo-1600.jpg 1600w" sizes="(max-width: 800px) 100vw, 800px" alt="Descriptive alternative text">
</picture>Do not publish a source URL unless the corresponding file exists and is encoded in the declared format. Keep the filename extension consistent with the actual bytes. Google says the HTTP Content-Type normally determines file type; an incorrect or missing header can lead to extension-based detection or reparsing. Configure your server MIME types correctly.
Browser rendering and Google Search are different checks
Google Search Central lists BMP, GIF, JPEG, PNG, WebP, SVG and AVIF as supported image formats for images referenced in an img element’s src. That is an indexing statement, not a complete browser-compatibility table. Check current audience-specific browser data before dropping a fallback. A crawler can index a format that an older client cannot render.
Use descriptive, accurate alt text, a standard img element and dimensions that prevent layout shifts. The Google Search Central Image SEO guidance explains the fallback and discoverability requirements.
A practical decision process
- Classify the asset. Choose photo, transparent/precise raster, vector, still animation or video-like animation.
- Set the visual requirement. Decide whether minor texture loss is acceptable, whether transparency is mandatory and whether wide-gamut or high-bit-depth output is needed.
- Encode candidates. Create JPEG/PNG fallbacks and WebP or AVIF alternatives. For vectors, keep the original SVG.
- Compare real files. Inspect text edges, gradients, skin tones, transparency and animation at the display size. Record byte size and an acceptable quality setting.
- Check clients. Use current browser data for your visitors, not a generic worldwide assumption. Keep
img srcwhen any meaningful audience needs it. - Deliver efficiently. Use responsive
srcset, correct MIME headers, dimensions, caching and lazy loading for below-the-fold images. - Recheck after changes. A new encoder, crop or quality setting can change the best format. Repeat the comparison for representative asset classes.
Common mistakes and fixes
Using JPEG for a transparent logo
JPEG has no transparency channel. Use PNG, WebP or AVIF with alpha, or an SVG logo when the artwork is vector-based.
Converting every PNG to JPEG
Text and flat edges can develop halos and ringing. Retain PNG or test lossless WebP/AVIF where precise reproduction matters.
Serving AVIF without a fallback
A client that cannot decode AVIF may show a broken image. Put AVIF first in picture, then WebP, then a conventional img src, as shown above.
Declaring the wrong MIME type
A file named .webp but served as another type can fail or be misinterpreted. Align bytes, extension and Content-Type.
Expecting a published average on every file
Google’s 26% and 25–34% figures are comparative averages under stated quality conditions. They are not a promise. Test your own assets.
Putting important images only in CSS
Google says CSS background images are not indexed as image content. Use an img element for content images and provide meaningful alternative text.
Best Value
Generating and checking files locally
Google’s WebP documentation provides cwebp and dwebp. A typical conversion workflow is:
cwebp -q 82 source.jpg -o source.webp
dwebp source.webp -o decoded.pngThe quality value is an example, not a universal recommendation. Compare the output visually and numerically, and retain the source master so you can re-encode later. For AVIF, use an encoder appropriate to your build pipeline and verify that the output decodes in your supported clients.
Or skip the browser setup
If your goal is a clean screenshot of a page rather than selecting an image format manually, ScreenshotNeo is a website screenshot API and MCP server for developers. One GET request returns PNG, JPEG, WebP or PDF. Before capture it accepts consent banners and removes more than 60 known consent platforms, newsletter popups and chat widgets; each step can be disabled. Bot checks/CAPTCHAs, blank pages, timeouts, failed loads and cache hits are not billed, and response headers identify the page verdict and billing result.
Use the API documentation at screenshotneo.com/docs/ for all options, including full-page and element captures, device and viewport settings, retina scale, custom CSS and JavaScript, waits, headers, cookies, blocking rules, geolocation, PDF controls, caching, signed links, asynchronous jobs, webhooks, bulk capture and usage reporting.
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curl -G "https://api.screenshotneo.com/v1/shot" -d access_key=YOUR_API_KEY --data-urlencode url=https://stripe.com -o shot.webpimport requests
r = requests.get("https://api.screenshotneo.com/v1/shot", params={"access_key": "YOUR_API_KEY", "url": "https://stripe.com"}, timeout=90)
open("shot.webp", "wb").write(r.content)const q = new URLSearchParams({ access_key: 'YOUR_API_KEY', url: 'https://stripe.com' });
const res = await fetch(`https://api.screenshotneo.com/v1/shot?${q}`);ScreenshotNeo includes an MCP server with take_screenshot, get_page_info and capture_pdf for Claude, Cursor and other MCP clients. The Free plan includes 1,000 shots per month with no card; paid plans start at $5 for 3,000 shots. Sign up free.
Cost, reliability and operational notes
- Generate variants during your build or image-processing pipeline, not on every request, unless you have a measured reason to do so.
- Cache immutable image URLs and set long-lived cache headers when filenames change on replacement.
- Monitor failed decodes, unexpected MIME types and fallback frequency in real clients.
- Keep source files and encoding settings under version control so a conversion can be reproduced.
- For screenshot services, inspect verdict and billing headers, retry transient timeouts, and avoid treating a cached response as a fresh page load.
Frequently Asked Questions
Should I use WebP or AVIF by default?
Choose by measured output and audience support. AVIF may compress better; WebP generally offers broader support and progressive rendering. Keep a fallback when required.
Can Google Search index WebP and AVIF?
Yes. Google Search Central lists WebP and AVIF among supported formats, but Search indexing support does not prove every browser can render them.
Is SVG better than PNG?
For scalable icons, interface artwork and diagrams, SVG stays crisp at different sizes. PNG is appropriate for raster screenshots, transparency and pixel-specific imagery.
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