What Is an AVIF File? A Plain-English Guide to the AVIF Format

So you've got a file sitting in your downloads folder with ".avif" at the end, and none of your usual apps want to open it. Or maybe a PageSpeed Insights report told you to "serve images in next-gen formats" and named AVIF specifically, and now you're wondering what that has to do with your website.

What is an AVIF file? In plain terms, it's a modern image format that squeezes a photo into a much smaller file than a JPEG or PNG, using compression technology originally built for video. You didn't choose this format. A website, an app, or your phone's camera chose it for you, which is exactly why it feels unfamiliar.

Here's what it is, how to open one today, and whether it belongs on your own site.

What Is an AVIF File, Exactly?

AVIF stands for AV1 Image File Format. The name is a bit of a mouthful, but the idea behind it is simple once you break it apart.

AV1 is a video compression format built by the Alliance for Open Media (AOMedia), a nonprofit group whose members include Google, Netflix, Mozilla, and Amazon. In 2019, AOMedia took that same compression technology and used it to encode a single still image instead of a moving one, then wrapped that image inside a HEIF container (the same type of container Apple uses for its own HEIC photos). The result is AVIF: a photo compressed with video-grade efficiency, sitting inside a standard image box (source: AOMedia, "AVIF Format"; MDN Web Docs' image file type and format guide, linked below).

Here's an analogy that might help: think of a HEIF container as a moving truck, and the compression method as the specific packing technique used to load it. A HEIC file is that truck packed the way Apple packs it. An AVIF file is that same truck, packed using AV1's method instead.

The truck looks similar either way. What's inside, and how efficiently it's arranged, is where the real difference sits. The analogy stops working if you try to open the box based on its shape alone, which is exactly why a file that ends in .avif won't always open in software built to expect a JPEG.

How do I open an AVIF file?

Here's the good news: you almost certainly already own something that opens AVIF files, whether it feels that way right now or not. Work through these in order, starting with the option that works regardless of what device you're on.

1. Open it in any modern web browser. Drag the file directly into an open browser tab, or right-click it and choose "Open with," then pick Chrome, Firefox, Edge, or Safari (version 16 or later). If it worked, the image displays exactly like any photo you'd view online.

   If nothing happens or you get a broken-image icon, your browser is probably out of date. Update it through the browser's own settings menu (look for "About" or "Help," then "Check for updates") and try again.

2. On Windows 11, just double-click it. No extra install is needed. Double-clicking should open the file in the Photos app, and you should also see a proper thumbnail preview in File Explorer rather than a generic icon.

   If neither happens, your Windows 11 installation may be missing recent updates. Check for updates under Settings, then Windows Update, and fall back to opening the file in a browser (step 1) while you wait for that to finish.

3. On Windows 10, install the free AV1 Video Extension first. Open the Microsoft Store, search for "AV1 Video Extension," and install it (despite the name, it also enables AVIF thumbnails and Photos support). Reopen the file afterward. You should now see a thumbnail in File Explorer and the Photos app should open it normally.

   If it still won't display, your build of Windows 10 may be too old to support the extension fully; the browser method from step 1 remains the most reliable fallback here.

4. On a Mac running macOS Ventura (13) or later, use Preview or Quick Look. Select the file in Finder and press the spacebar for a quick preview, or double-click to open it fully in Preview. You should see the image render normally in either case.

   If it doesn't, you're likely on macOS Monterey or an earlier version, which doesn't support AVIF natively. Opening it in a browser works around this, or you can update macOS if your Mac supports the newer version.

5. On an iPhone or iPad running iOS or iPadOS 16 or later, just tap it. Open the file from the Files app, Messages, or Mail, and it should display like any photo, with no extra steps. If it won't open, check whether your device is running an older iOS version under Settings, then General, then Software Update. Opening the attachment in Safari is a reasonable workaround if you can't update right away.

6. If you need to edit the file, not just view it, expect some friction. Design software has lagged behind browsers on this one. Photoshop's AVIF support is inconsistent depending on version, and Adobe's own community forums have active threads from users asking when full AV1 support is coming. If your goal is simply to get a JPG version for editing in an older tool, converting the file (avif to jpg) through a browser-based converter is a perfectly reasonable quick fix, even if it's not something this site's tool does for you.

Which browsers support AVIF?

All four major browsers support AVIF today, though they got there at different times. Chrome and Opera added support first, back in 2020 (from Chrome desktop version 85). Firefox followed in 2021. Safari was last, adding support in 2022 with Safari 16, tied to macOS Ventura and iOS 16, which is exactly why older Apple devices are the most common place people run into trouble opening these files.

Google's own web.dev Baseline project puts it simply: AVIF has been supported by all core browsers since January 2024 (web.dev, "Baseline 2024: more tools to help web developers"). That's a useful marker if you're trying to answer the "is this safe to use yet" question for your own site. It's not brand new and experimental anymore; it cleared that bar a couple of years ago. For the current global support percentage, which shifts slightly over time as older browser versions fall out of use, caniuse.com/avif tracks the live figure rather than a number that will go stale in an article like this one.

What AVIF format does well

Compression is the headline feature, and it's a genuinely large improvement, not a marginal one. MDN cites AVIF as producing files roughly 50% smaller than an equivalent JPEG at similar visual quality. For comparison, WebP typically manages around a 30% improvement over JPEG. AVIF generally beats WebP too, though the gap narrows depending on the type of image (source: MDN Web Docs, Image file type and format guide).

For a photo-heavy site, that translates directly into faster page loads, which matters both for visitors on slow connections and for how Google evaluates your page's loading speed. If switching formats isn't practical yet, our guide on how to reduce image file size covers compression settings that shrink the JPEGs and PNGs you already have.

What makes AVIF unusual is that it's not just good at compression. It's the only mainstream web image format that covers all of the following at once, according to AOMedia and MDN's documentation:

• Lossy compression (smaller files, some quality trade-off) and lossless compression (no quality loss at all)
• Alpha-channel transparency, the same kind of see-through background PNG offers
• Animation, similar to GIF but at a fraction of the file size
• HDR (high dynamic range) and wide color gamut, useful for photography with a lot of contrast between bright and dark areas

If your site handles product photography, illustrations with transparent backgrounds, or short looping animations, AVIF is worth a look specifically because it doesn't force you to pick a different format for each of those needs the way older formats do.

The trade-offs nobody mentions

It's not a free upgrade in every direction, and it's worth being honest about that before you switch anything.

AVIF doesn't support progressive rendering. A JPEG can load blurry and sharpen as more data arrives, so a visitor sees something on screen almost immediately. An AVIF file has to finish downloading before it displays anything at all.

MDN notes this matters less in practice than it sounds, because AVIF files are so much smaller to begin with that the whole download usually finishes quickly anyway. Still, on a genuinely slow connection, a large AVIF image can feel like it's taking longer to appear than a JPEG would, even though the total download is smaller.

There's also a decode cost. Multiple independent technical write-ups converge on the same pattern: AVIF wins clearly on file size, but WebP decodes faster and uses less processing power and battery to display. That matters more on older or lower-power mobile devices rendering a lot of images at once.

This isn't a reason to avoid AVIF outright; for most sites, the bandwidth savings outweigh the modest decode overhead. It's simply a trade-off worth knowing about rather than a hidden catch.

And as covered above, creative software support still lags noticeably behind browser support, which is the gap that trips up the most people day to day.

Is AVIF smaller than WebP?

Generally, yes. Based on MDN's figures, AVIF's roughly 50% size reduction over JPEG outpaces WebP's roughly 30% reduction over the same baseline, which puts AVIF ahead on file size for most images, with the gap narrowing on certain image types. If you want the fuller picture, including when WebP might actually be the more practical pick for your setup, our WebP vs JPEG comparison covers that ground in more depth than a rushed paragraph here could.

Should your site use AVIF? A simple checklist

Here's a short, non-vendor way to answer this for your own site, without needing to hire anyone or buy a subscription first.

• Check your CMS and host support. WordPress added native AVIF upload support in core version 6.5 (March 2024), meaning the Media Library accepts AVIF files and generates thumbnails automatically, provided your host runs PHP 8.1 or later with GD or Imagick compiled to support the format. If you're on an older WordPress version or a different platform, a plugin or manual export step may be needed instead.
• Think about your audience's devices. If a meaningful share of your visitors are on Safari versions older than 16 or on devices that haven't updated in a while, AVIF alone will leave some of them without an image at all, unless you provide a fallback.
• Check whether you're already using WebP with a fallback. If your site already serves WebP through a <picture> element with a fallback source, adding AVIF is a smaller step than it sounds. It slots in as an additional, higher-priority option in that same markup rather than requiring you to rebuild your image pipeline from scratch.

None of this requires a full rebuild. It's closer to swapping one ingredient into a recipe you're already using than starting the recipe over. And while you're auditing formats, it's a good moment to check that the images themselves are still doing their other job properly. Our alt text guide covers what to write for each kind of image, since a smaller file that nobody can describe to a screen reader is only half the win.

How to check what format your site is actually serving

Here's the part most articles on this topic skip entirely: how do you know what format your site is currently sending to visitors, right now, without guessing? A file named "photo.jpg" doesn't guarantee the server is actually sending a JPEG. Servers sometimes negotiate a different format behind the scenes, and CMS plugins occasionally mislabel files without anyone noticing.

The imagecheck.tools checker solves exactly this. Paste in a URL, and it reads each image's real format straight from its file bytes rather than trusting the file extension, then reports it alongside file size and pixel dimensions for every image on the page. It's a fast way to see, in one pass, whether your site is already serving modern formats like AVIF or WebP, or whether every image on the page is still a full-size JPEG waiting to be optimized. It also flags images sent without a Cache-Control header, so repeat visitors download them every time.

Frequently Asked Questions

What is an AVIF file?

An AVIF file is a still image compressed using AV1 video technology and stored inside a HEIF container, the same type of packaging Apple's HEIC photos use. It was released by the Alliance for Open Media in 2019 and typically produces noticeably smaller files than JPEG or PNG at a similar visual quality, which is why browsers and CMS platforms increasingly recommend it for web images.

How do I open an AVIF file?

The fastest, most reliable way is to open it in any modern web browser, including Chrome, Firefox, Edge, or Safari 16 and later, since all of them display AVIF files directly. Windows 11, macOS Ventura and later, and iOS or iPadOS 16 and later all open AVIF files natively without needing any extra software. Windows 10 needs the free AV1 Video Extension from the Microsoft Store first, and older creative tools like Photoshop may still have limited support even when your browser handles the file just fine.

Which browsers support AVIF?

Chrome and Opera added AVIF support in 2020, Firefox followed in 2021, and Safari added it in 2022 with Safari 16. According to Google's web.dev Baseline project, AVIF has been supported by all core browsers since January 2024, making it a safe, well-supported choice for most website audiences today.

Is AVIF smaller than WebP?

Generally, yes. MDN's documentation cites AVIF as producing files roughly 50% smaller than JPEG at comparable quality, compared to a typical 30% reduction for WebP over the same baseline, which puts AVIF ahead on compression for most images, though the exact gap varies by image type.