JPEG vs WebP vs AVIF: Which Format Should You Use in 2026?

Written and reviewed by the Compress To KB editorial team. Last updated September 24, 2026. We build and maintain the compressor this guide refers to, so what we say about how it behaves comes from its actual code and from day-to-day use, not from guesswork.

Ask three developers which image format to use and you will probably get three confident answers. The honest one is: it depends on where the image is going. JPEG, WebP and AVIF each solve the same problem, storing a picture in as few bytes as possible, but they make different trade-offs around size, compatibility, speed and features. This guide compares them as they stand in 2026 and ends with a decision table you can use without reading anything else.

JPEG: Old, Boring and Everywhere

JPEG dates from the early 1990s and remains the default format for photographs. It is decoded by every browser, phone, printer, email client, content management system and government upload form ever made. That universality is its main advantage. Technically it works by cutting the image into 8×8 blocks and rounding off fine detail, as we describe in our guide to lossy and lossless compression. The weaknesses are equally well known: it has no transparency, it produces visible blocks and speckles when pushed to very small sizes, and it is less efficient than newer formats, so the same visual quality costs more kilobytes.

WebP: The Practical Upgrade

Google released WebP in 2010, built on the intra-frame technology from its VP8 video codec. According to Google's own published comparisons, lossy WebP files are commonly 25–34% smaller than JPEGs of similar quality, though results vary by image. It supports lossless compression, transparency (in both lossy and lossless modes) and animation, which lets one format replace JPEG, PNG and GIF in many situations. Support is now effectively universal in current versions of Chrome, Edge, Firefox and Safari; you can confirm the details on Can I use. The remaining gaps are outside the browser: some older desktop software, email clients and upload forms still reject it.

AVIF: The Size Champion

AVIF stores images using the key-frame technology of the AV1 video codec, developed by the Alliance for Open Media. In most comparisons it produces the smallest files of the three, often around half the size of an equivalent JPEG in favourable cases, and it handles smooth gradients and low-bitrate images noticeably better than the older formats. It also supports transparency, high bit depth and HDR. The costs are slower encoding, a slightly more complicated ecosystem and more uneven support outside browsers. Current browsers decode it (see Can I use for versions), but decoding and encoding are different things: a browser that can display AVIF may not be able to produce it, so tools that run in the browser have to check what the visitor's browser can actually output.

Side by Side

What "Auto" Does in Our Tool

Because you choose a target size on each page, the compressor has to pick a format for you unless you say otherwise. In Auto mode it follows a simple sequence. If the image contains real transparency, it prefers WebP. Otherwise, for targets of 75KB or less, it uses AVIF when your browser is able to encode it. For everything else it uses WebP when supported, and falls back to JPG (or PNG for an original PNG). That logic is why the same page can return different formats in different browsers, and why the small tiers such as the 20KB and 50KB pages are where AVIF makes the biggest difference. If you need a specific format, use the Output Format dropdown and the tool will honour it, falling back to a supported alternative only if your browser cannot produce the format you asked for.

When You Must Use JPEG

Compatibility beats efficiency whenever someone else's system decides. Exam and government portals overwhelmingly specify JPG or JPEG and will reject anything else, so choose JPG explicitly, as we explain in our guide to passing photo upload validators. Email newsletters should also use JPEG, because a few desktop clients render WebP and AVIF poorly or not at all. The same goes for images you will hand to a printer or an unknown recipient, and for any workflow that ends in a program you have not tested.

When WebP Is the Sensible Default

For images you publish on your own website or store, WebP is usually the best balance: clearly smaller than JPEG, supported by all current browsers and quick to encode. Blog images, product thumbnails, social graphics and anything with a transparent background all suit it. The 100KB, 150KB and 200KB pages (100KB, 150KB, 200KB) are typical places for it in Auto mode. If you run an online shop, our guide to e-commerce image optimisation shows how to combine format and target size by image role.

When AVIF Earns Its Extra Complexity

Choose AVIF when bytes are scarce and you control the delivery: hero images on mobile-first pages, image-heavy landing pages, or any case where trimming a further 20–30% off an already optimised WebP will visibly improve loading. Pair it with a fallback. On a site you manage, the HTML picture element lets you list AVIF first, WebP second and JPEG last, and each browser picks the first one it understands. That is the approach we would suggest to anyone chasing the Largest Contentful Paint scores we discuss in our Core Web Vitals guide.

What About HEIC and Other Formats?

Photos from recent iPhones may be saved as HEIC, another modern format with strong compression but very limited browser support. Compress To KB does not accept HEIC files directly. If your phone offers it, change the camera format to "Most Compatible" or export the image as JPG before uploading it to the tool. GIF and BMP inputs are accepted, and you can convert them to JPG, PNG, WebP or AVIF through the output dropdown.

Quality Is Not the Same as Size

One more misconception is worth clearing up. "AVIF is smaller" does not mean "AVIF looks worse". At a given file size, the newer formats usually look better than JPEG, because their encoders are smarter about where to spend bytes. But at any format, an image forced into a very small target will show artifacts, and no format rescues a blurry original. If your result looks too soft, choose a higher target rather than a different format.

Decision Table

If you are unsure, start with a JPG, then try WebP and compare the file sizes and appearance on your own picture. A few minutes of testing on your actual images beats any general rule, ours included.

Why the "Best" Format Keeps Changing

It is worth remembering that this comparison is a snapshot of 2026, not a permanent ranking. JPEG's dominance lasted for decades because no format offered enough of an improvement to justify the compatibility cost of switching. WebP crossed that bar for the web a few years after its release, once every major browser could decode it. AVIF is still completing that journey: encoding tools, content management systems and some downstream software are gradually catching up to what browsers can already display. A format's real-world usefulness depends less on its technical ceiling and more on how completely the rest of the ecosystem, including the app you are uploading to, has adopted it. Revisit this choice every year or two rather than assuming today's answer is permanent.

Testing Formats on Your Own Images

The comparisons above are general tendencies, not guarantees for every photo. The fastest way to know what works best for a specific image is to compress it as JPG, then again as WebP, at the same target size, and look at both side by side at the resolution they will actually be displayed. Pay particular attention to any fine text, thin lines or subtle gradients in the picture, since that is where differences between formats show up first. Keep whichever result looks cleaner to your own eyes; the "average" advantage of one format over another will not matter if your specific photo happens to compress better in the other one.