# Default behavior of system.tag.write in 8.0.x

**URL:** <https://forum.inductiveautomation.com/t/default-behavior-of-system-tag-write-in-8-0-x/38413>\
**Category:** Ignition\
**Created:** [September 4, 2020, 5:25pm UTC](https://forum.inductiveautomation.com/t/default-behavior-of-system-tag-write-in-8-0-x/38413 "2020-09-04T17:25:54Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![greg.krueger](https://avatars.discourse-cdn.com/v4/letter/g/5f9b8f/32.png) [@greg.krueger](https://forum.inductiveautomation.com/u/greg.krueger)\
**Post date:** [September 4, 2020, 5:25pm UTC](https://forum.inductiveautomation.com/t/default-behavior-of-system-tag-write-in-8-0-x/38413/1 "2020-09-04T17:25:54Z")

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With the introduction of the .writeBlocking/.writeAsync methods in 8.0, my understanding is that system.tag.write was deprecated, but we still use it in our logic and it still works (I’m assuming for backwards compatibility)…can anyone tell me which function is actually being called when you don’t explicitly call it with the Blocking or Async suffix?  
I thought it was using the Blocking one as that does not require the use of a callback (and our .write calls just have tagname and value no other arguments). But a colleague of mine saw some timestamp issues on some scripting he had and changed it from .write to .writeBlocking and says that changed the behavior of the writes.

In the user manual if you click on hyperlink references to system.tag.write it goes to the .writeAsync page. So that seems to indicate Async is the default behavior…so maybe if no callback is provided, it has a default/dummy callback it runs for you?

Any clarification is appreciated.

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**Author:** ![paul-griffith](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/paul-griffith/32/37249_2.png) [@paul-griffith](https://forum.inductiveautomation.com/u/paul-griffith)\
**Post date:** [September 4, 2020, 5:31pm UTC](https://forum.inductiveautomation.com/t/default-behavior-of-system-tag-write-in-8-0-x/38413/2 "2020-09-04T17:31:00Z")

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`writeAsync` _is_ the only implementation as of 8.0. Both `writeBlocking` and the “legacy” `write` function simply call `writeAsync`, and then block further code execution (for a specific period of time) waiting for the result to come back. All three functions go through the same code path, and as a result the actual time _for a value to be written_ should be the same no matter what.