Hello World vs. Hello Apple: What Do You See When You Look at This Image?

We all remember the“What color is this dress?”phenomenon followed by“Yanny vs. Laurel . ”Now the world has a unexampled puzzle to obsess over , and it will pit Apple users against their longtime rivals .

Here ’s how it work : look atthis imageon a personal computer or Android phone ( or any other non - Apple Cartesian product ) . Then , view the same image on an Apple twist . If you were already using a Mac , iPhone , or iPad , then switch over to a different platform .

allow ’s try that again with adifferent image .

Screenshot examples of how all four variations look to different users.

Screenshot examples of how all four variations look to different users.Image: David Buchanan

Pretty neat , huh ? When viewing the first image on a PC or Android earpiece , you should have seen the message “ HELLO WORLD . ” On an Apple equipment that same image filing cabinet read “ HELLO APPLE . ” ( There is a caveat that we ’ll come up to in further detail below . )

The 2nd double is even trippier . On a non - Apple equipment , the image prove an honest-to-god IBM personal computer , but switch to an i - gimmick and you ’ll see an old Mac .

OK , so what the hell is plump on here ? Let engineer and cryptographer David Buchanan — the mastermind behind this mystifier — do the explaining :

Image: David Buchanan

Image: David Buchanan

“ I ascertain this while publish my own multi - wind PNG decoder . While excogitate my design , I realised that I had an exploitable implementation microbe , ” Buchanan wrote in ablog post . “ After learning that Apple has their own implementation of parallel - decodable PNGs , I realise that they ’d made just the same mistake ! ”

In simplified terminal figure , there are different ways to decode an ikon . You could do it in a undivided train of thought or you could do it in parallel threads demote into occlusion ( a method acting used to make programs run faster ) , as Buchanan attempted . He discovered a germ in his own project , then regain that Apple had made the same fault . He make up one’s mind that it was potential to render a PNG file cabinet where : decompress(a + b ) ! = decompress(a ) + decompress(b ) ( where ! = means not equal to ) . That is , that two piece decoded separately then put together did n’t always create the same results as those same two parts decipher together .

“ This could bump if a ends halfway through a non - compressed closure . It is , therefore , possible for an range of a function to have two possible interpretations , depending on whether a parallel or non - parallel decipherer decodes it , ” Buchanan continue .

Image: David Buchanan

Image: David Buchanan

For you skeptics out there , when I showed these images to my brother , a inquiry scientist at The University of Virginia , he hash the files ( convert them into numbers ) and confirm that they are indeed the same , demonstrate thatBuchananisn’t cutting corners by serve you different files based on the browser app or OS you ’re using .

If you ’re having bother repeat this puzzle , it may have to do with your web browser app because the john relies on Apple computer software , not computer hardware . After viewing the image on multiple devices and web internet browser , we find out that Apple products running Safari will always show HELLO APPLE while non - Apple devices using other browsers show HELLO WORLD .

But things do get puzzling once you embark on merge and matching .

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When using non - Safari web browser on Apple ’s roving twist ( iPad , iPhone ) , the HELLO APPLE subject matter appeared . queerly , using those same internet browser — Chrome , Opera , Edge , for example — on a Mac showed the HELLO WORLD message . While we ca n’t be sealed , this paint a picture internet browser apps write for the App Store are using Apple ’s PNG render persona library whereas browsers downloaded as programme on macOS use their own PNG parser .

Whatever the typeface , if you want to get in on the merriment , Buchanan posted a tool called‘Ambiguous PNG Packer’that lets anyone create images that expect different when scat through Apple software . We should caution , however , that these deviations in parsing picture file could be a security department business concern , and something Buchanan believes “ needs to be approached with care . ”

Update at 1:30p ET : We in the beginning published this article with embedded photos . alas , our CMS vary the file enough to break the phantasy . We ’ve update the article with links that will take you to photograph that should face dissimilar on Apple vs. other platforms .

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