Which Image Formats Each Platform Accepts

Modern commerce platforms accept WebP and increasingly AVIF, print and legal workflows accept neither, and email clients sit awkwardly in between. JPEG and PNG remain the only 2 formats accepted everywhere without a caveat.

Accepting a format and preserving it are different things. Several platforms take your WebP file and re-encode it to JPEG behind the scenes, which means you carry the compatibility risk without receiving the size benefit. Knowing which platforms do this changes what you should upload.

Format support by platform

Check the last column before choosing an upload format, because a platform that re-encodes everything makes your format choice irrelevant. Support changes over time, so confirm against current documentation before a large migration.

The pattern in that table is consistent. Systems built recently for the web accept modern formats, and systems built for print, compliance or legacy compatibility do not. Age of the system predicts format support better than the size of the company running it.

Browsers are not the problem any more

Every current browser supports WebP, including Chrome, Firefox, Safari and Edge on desktop and mobile. Safari added support in 2020, which ended the last serious compatibility argument against the format.

AVIF sits a step behind, with support in all major browsers but less consistent behaviour in older versions and some embedded viewers. For a public website, WebP is safe without a fallback and AVIF is safe with one. The remaining problems are outside browsers entirely.

Why platforms re-encode your uploads

Platforms re-encode to control their own delivery costs and to serve the right size to each device. A marketplace showing an image in 6 different layouts needs 6 variants, and generating them from one upload is simpler than asking sellers to supply them.

Re-encoding has a consequence worth understanding. Uploading a heavily compressed file gives the platform a damaged source to work from, and the damage carries into every variant. Where a platform re-encodes, upload a high quality file at correct dimensions and let the platform handle the compression, rather than compressing twice.

Where WebP genuinely helps

WebP helps most on sites you control, where the file you upload is the file a visitor downloads. Your own website, a self hosted store and a documentation site all fall into that category.

• Your own website. Full benefit, since nothing re-encodes the file.
• Self hosted stores. Full benefit, and page speed affects conversion directly.
• Content systems that generate variants. Partial benefit, because the platform decides the output.
• Marketplaces. No benefit, since uploads are re-encoded regardless of what you send.
• Social networks. No benefit, as every network converts to its own format.

Where WebP causes problems

Avoid WebP anywhere a human will download the file and open it in software outside a browser. Design tools, office software and print workflows still handle the format poorly.

The most common failure is a press kit or a media pack. A journalist downloading a WebP logo may be unable to place it in their layout software, and the request goes unanswered rather than returned. Government upload forms are the second common failure, where validation refuses the format outright with an error that rarely names the cause.

How to decide which format to upload

To choose correctly, answer these 4 questions in order.

1. Will the file be downloaded and opened outside a browser? If yes, use JPG or PNG.
2. Does the platform re-encode uploads? If yes, upload high quality JPG or PNG and let the platform decide.
3. Do you control delivery of the file? If yes, use WebP, with AVIF on your heaviest images.
4. Does the image need transparency? If yes, use PNG or WebP, since JPEG has no transparency channel.

Those 4 questions resolve almost every case without needing a compatibility table. The underlying principle is simple: modern formats belong where you control the pipeline, and universal formats belong everywhere else.

Serving modern formats safely on your own site

Use a picture element listing AVIF first, WebP second and a JPEG fallback in the img tag. The browser takes the first format it understands, so newer browsers get the small file and older ones still get an image.

The markup costs a few lines per image and removes compatibility risk entirely. Most content systems and site builders now generate the pattern automatically on upload, so check what your platform already does before writing it by hand. Converting the images takes a couple of minutes, while writing the markup usually takes longer.

How to check what a platform really accepts

Upload one test file and inspect what the platform serves back, since documentation is frequently out of date. The answer takes 2 minutes and is more reliable than any published list.

Upload a WebP image, view the published page, right click the image and open it in a new tab. The file extension in the address bar shows what the platform is actually serving. A .jpg extension means your WebP file was converted, while a .webp extension means it was preserved. Repeat the test after any major platform update.

Formats that are quietly disappearing

BMP, TIFF and animated GIF still work almost everywhere and are the wrong choice in nearly every case. Each survives because old software produced it, rather than because it does anything well.

BMP stores images with almost no compression, so a screenshot can weigh 20 times its PNG equivalent. TIFF remains standard in printing and scanning and is unusable on the web. Animated GIF is limited to 256 colours and frequently weighs more than a short video of the same clip. Converting these 3 formats on receipt, rather than storing them, avoids carrying the weight through a whole workflow.

Planning a format migration

Convert a copy of the library rather than the originals, and keep the originals until the new files are live and verified. Format migrations are one of the few image tasks that can lose work permanently.

Work in 4 stages. Audit which images are actually used, since most libraries carry files no page references. Convert a copy to the target format at correct dimensions. Publish the new files alongside a fallback so nothing breaks during the switch. Only remove the originals once the pages have been checked on a phone, a desktop browser and any client system that consumes the images.

What about AVIF

AVIF compresses roughly 20 to 30 percent harder than WebP on large photographs and encodes far more slowly. The format is worth the extra effort on hero images and photography heavy pages.

Below about 10 KB a WebP file is often smaller, because AVIF carries more container overhead than tiny images can justify. Use AVIF on your largest images, WebP everywhere else on the site, and keep a JPEG fallback for both. Platform support outside browsers is still thin, so AVIF belongs on sites you control rather than on files you hand to other people.

Converting a library for a specific destination

Convert once to the format the destination actually uses rather than converting repeatedly between formats. Each lossy conversion discards detail, so a file that has passed through 3 formats carries 3 generations of loss.

Decide the destination first, then convert directly from the original. Our converters handle every common pairing, including HEIC, PNG, JPG, WebP, AVIF, GIF and BMP in both directions, so there is no need to route a file through an intermediate format. Batches of up to 500 files run at once, entirely inside your browser, which means an entire image library can be prepared for a migration without a single file leaving your machine.