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Fixed in 2020.3.47f1, 2021.3.22f1, 2022.2.12f1, 2023.1.0b9, 2023.2.0a6



Found in



Issue ID




[FBX-SDK] Unity Editor not responding and uses up all the memory while importing old FBX with multiple animations



Importing Old FBX files exported with FBX 6.1 (before FBX SDK 2011) and containing multiple animations will grow the memory usage exponentially with the number of animation takes in the file.

This is a bug in the latest FBX SDK (2020.3.1) and will be fixed in the upcoming update. This is out of our control (external to Unity) but is expected early March.

Temporary Workaround: Using the FBX Converter ( on the affected files to convert them from 6.x to 7.3 will avoid the issue


# Open attached project with 2023.1.0a26
# While opening project, press "Ignore" and ignore errors
# See that memory usage by Unity is increasing

Result - Notice that editor gets stuck on importing "Idl3.fbx" or other fbx file. Memory usage keeps on growing, until mac asks to shut down some programs. In logs it doesn't show anything more except importing this model

Reproducible with - 2023.1.0a25 eac607654885, 2023.1.0a26 c80c0f25543e

Not reproducible with - 2023.1.0a24 f576cc309ca2

Reproduced on MacOS 12.2 and 13.1, Windows 10. (Happens on all OS but M1 is more affected)


  1. Resolution Note (fix version 2023.2.0a6):

    Fixed in 2023.2.0a7

  2. Resolution Note (fix version 2023.1.0b9):


    Revision: 2023.1/staging 824d2f8c920d
    Built: Wed, 15 Mar 2023 02:38:28 GMT

  3. Resolution Note (fix version 2022.2.12f1):

    Fixed in 2022.2.13f1

  4. Resolution Note (fix version 2021.3.22f1):


    2021.3.22f1.git.11978065 Personal
    Revision: 2021.3/staging b6c551784ba3
    Built: Tue, 21 Mar 2023 13:41:09 GMT

Comments (1)

  1. wagenheimer

    Mar 02, 2023 17:46

    This bug has been observed to occur on all Unity LTS versions newer than 2021.3.16.

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