[_Microft]

Cameras usually include an infrared filter (also called a "hot mirror" or "IR cut") that reflects infrared radiation. Mostly because not blocking IR leads to wrong colours for scenes like sunsets where a disproportionate amount of IR radiation is there.

Many smartphones (used to?) exclude this filter on the selfie-camera because no matter how hot you think you might be, it's not going to be an issue.

If you want to check an IR remote for function, try with the selfie camera of your phone and not the normal one and make sure you are trying in a dark environment because the LED on the remote is going to be rather dim either way.

https://en.wikipedia.org/wiki/Hot_mirror

[equalsione]

As an aside, the IR filter is often removed[0] from many cameras when using them for astrophotography. Canon[1] sell dedicated astro cameras that are modified in this way, along with other modifications.

[0] - https://skyandtelescope.org/astronomy-blogs/imaging-foundati... [1] - https://www.canon.co.uk/cameras/eos-ra/