"This File Type Is Not Supported": Fixing Rejected WebP Uploads

You have an image. The upload form has rejected it with some variation of "unsupported file type", possibly after making you wait for the full upload first. The file is a .webp, and the form's allowlist was written before WebP existed.

The fix is always to convert — but which format depends on what is on the other end, and the reflexive answer of "JPG" is sometimes wrong.

Application portals, job sites, government forms

Convert to PDF. These systems usually want a document, not an image, and many reject bare image uploads even in supported formats. Wrapping the image in a properly sized A4 or Letter page turns it into something they will accept — and if you have several images to submit, merging them into one paginated PDF is far more professional than a folder of separate attachments.

If the form explicitly asks for an image, use JPG.

Photo printing, kiosks, print-on-demand

Convert to JPG for consumer services, TIFF for professional ones. Retail photo kiosks and consumer print services want JPG and nothing exotic. Commercial printers, magazine prepress and print-on-demand platforms typically specify TIFF because it is lossless, carries ICC colour profiles, and holds DPI metadata reliably.

Be aware of what conversion cannot do here: a lossless TIFF wrapped around already-lossy WebP pixels does not recover quality the WebP encoder discarded, and it cannot invent the 16-bit depth or CMYK separation a true prepress file would carry. If the work is genuinely print-bound, the WebP should never have been the master in the first place.

Design tools and document software

Convert to PNG if there is any transparency, JPG otherwise. Figma, Canva, Illustrator, InDesign, Word and PowerPoint all accept PNG without argument. Crucially, PNG preserves the alpha channel — converting a transparent logo to JPG composites it onto a white box, which is almost never what you want and is surprisingly easy not to notice until it is in front of a client.

Email attachments

Convert to JPG or PNG. Do not send a .webp by email under any circumstances. Outlook renders through Word's HTML engine and will not display one inline, and enough recipients will be on software that cannot open the attachment that it is simply not worth the risk.

Marketplaces and social platforms

Convert to JPG or PNG and check the listed dimension requirements while you are at it. Etsy, eBay, Amazon Seller Central and most marketplace back-ends publish explicit format and size rules, and a rejection is as likely to be about dimensions or aspect ratio as about the format.

Legacy and internal business systems

JPG first; BMP if that fails. Industrial control panels, lab instruments, medical imaging stations and embedded systems sometimes accept only uncompressed bitmaps. BMP is enormous — often 15 to 40 times the WebP — but it is the lowest common denominator that any software from any decade can read.

A note on batches

If you are converting more than a couple of files, do it as a batch rather than one at a time. Queue the whole folder, get a single zip back, and upload from that. It is also worth converting one file first and testing the upload before committing to the full set — occasionally the rejection turns out to be about file size or dimensions rather than format, and you will have converted fifty files for nothing.