# Will FMOD callbacks always happen on the main thread?

**URL:** <https://qa.fmod.com/t/will-fmod-callbacks-always-happen-on-the-main-thread/17703>\
**Category:** FMOD Engine\
**Created:** [September 22, 2021, 5:31pm UTC](https://qa.fmod.com/t/will-fmod-callbacks-always-happen-on-the-main-thread/17703 "2021-09-22T17:31:53Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![wills](https://yyz2.discourse-cdn.com/flex036/user_avatar/qa.fmod.com/wills/32/2641_2.png) [@wills](https://qa.fmod.com/u/wills)\
**Post date:** [September 22, 2021, 5:31pm UTC](https://qa.fmod.com/t/will-fmod-callbacks-always-happen-on-the-main-thread/17703/1 "2021-09-22T17:31:53Z")

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[The docs say](https://www.fmod.com/resources/documentation-api?version=2.02&page=white-papers-threads.html#fmod-callback-types):

FMOD Callback Types  
FMOD File and memory callbacks can possibly be called from an FMOD thread. Remember that if you specify file or memory callbacks with FMOD, to make sure that they are thread safe. FMOD may call these callbacks from other threads.

Does this mean that **all other callback types** (including `FMOD_CHANNELCONTROL_CALLBACK_END`) will always be called from the main thread?

In my experiments, `FMOD_CHANNELCONTROL_CALLBACK_END` _is_ called on the main thread.

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<div class="post-metadata">

**Author:** ![mathew](https://yyz2.discourse-cdn.com/flex036/user_avatar/qa.fmod.com/mathew/32/431_2.png) [@mathew](https://qa.fmod.com/u/mathew)\
**Post date:** [September 22, 2021, 11:31pm UTC](https://qa.fmod.com/t/will-fmod-callbacks-always-happen-on-the-main-thread/17703/2 "2021-09-22T23:31:31Z")

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All the ChannelControl callbacks will fire from the main (calling) thread, unless you are using the Studio API, in which case they will fire from the Studio Update Thread (in default / async mode) or the main (calling) thread in synchronous mode.

I’ve scheduled a task to have this information added to the documentation for all callbacks.