My htc one sv is stuck in boot loop

We might have more idea if we knew whether anything happened before this started, e.g. a software update, or whether the phone has ever got wet (water damage can cause problems some time after the incident).

Without further information the best I could suggest would be completely reflashing the software. For this you need to find the correct ROM Update Utility for your phone. Unfortunately this not only has to be for the One SV, but it must be for a One SV of the same "customer id", i.e. the region & carrier the phone was originally sold to. And the software version must be no older than what you have installed, as these things won't downgrade the software.

You can find a few of these things here, but not many I'm afraid (and only the ones starting "RUU" are candidates - "OTA" means a patch update file rather than a complete set of software). Not knowing your phone's details I don't know whether any of these will be suitable.

If one is suitable, the procedure is to download the RUU, which is a Windows .exe, onto a PC. Connect the phone via USB and put it in fastboot mode (reboot it while pressing the "volume down" key. If the screen you get says "hboot" rather than "fastboot" then select "fastboot" from the menu of options). Run the RUU .exe on the PC and follow the prompts. If the RUU is wrong for the phone it will refuse to run. Do not interrupt it if it does run, and make sure the phone is properly charged before you start (interrupting while it is reloading the phone could mess things up even worse).

Good luck.

 

Sometimes we overlook the obvious stuff. If the phone is in a case, try removing it and see if the problem persists. It's possible to trap a piece of dust or lint between the phone and case, causing one or more buttons to be partially depressed. The phone thinks the button is being held down continuously, and thus the bootloop. Even without a case it's possible. If you can, try hitting the physical buttons with a blast of compressed air. It might do nothing, but then again it could solve your problem. GL!

 

Do you have a windows PC? If yes, you can try Dr.Fone for Android. Run the software and connect your HTC to computer with a USB cable. Dr.Fone will detect your HTC and let you restart your HTC to go back to normal.