The Verge:

Bryner is among the many high school students around the country who completed Advanced Placement tests online last week but were unable to submit them at the end. The culprit: image formats.

A screenshot of the AP testing portal informing a student that they weren’t able to submit their responses. Screenshot: College Board For the uninitiated: AP exams require longform answers. Students can either type their response or upload a photo of handwritten work. Students who choose the latter option can do so as a JPG, JPEG, or PNG format according to the College Board’s coronavirus FAQ.

But the testing portal doesn’t support the default format on iOS devices and some newer Android phones, HEIC files. HEIC files are smaller than JPEGs and other formats, thus allowing you to store a lot more photos on an iPhone. Basically, only Apple (and, more recently, Samsung) use the HEIC format — most other websites and platforms don’t support it. Even popular Silicon Valley-based services, such as Slack, don’t treat HEICs the same way as standard JPEGs.

If they had tried testing it with the most commonly used devices they would have noticed this bug instead of only discovering it after rollout.