Chrome will remove BMP extension for embedding JPEG-or-PNG-in-BMP for the following reasons: Security ======== We have compelling evidence that surprising and rarely-used support for nesting formats is a path to security bugs. Such a possibility is especially worrying for BMP, which is otherwise considered a pretty simple format. Interoperability ================ * Today only Chrome supports this BMP extension. (Tested with Chrome 141.0.7390.134, Firefox 143.0.4 and 144.0.2, Safari 18.6) * There is no official spec. * Mozilla Developer Network advises against using BMP in general, and this BMP extension specifically (calling it only “theoretically supported”) No usage ======== No usage has been registered via UMA data (see https://crbug.com/452667935). Not just minimal usage, but no usage whatsoever. Viable alternatives =================== If our research data missed an existing usage of JPEG-or-PNG-embedded-in-BMP then we kindly ask web developers to use PNG and/or JPEG images **directly** rather than embedding them inside a BMP format.
We plan to: * Have no deprecation period (because UMA registered no usage). * Ship the removal behind a Finch kill switch / behind an enabled-by-default `base::Feature`.