# Can we write out the old VTK 4.2 file format with VTK 9?

**URL:** https://discourse.vtk.org/t/can-we-write-out-the-old-vtk-4-2-file-format-with-vtk-9/5066
**Category:** Development
**Tags:** file-formats
**Created:** [January 26, 2021, 6:34pm UTC](https://discourse.vtk.org/t/can-we-write-out-the-old-vtk-4-2-file-format-with-vtk-9/5066 "2021-01-26T18:34:18Z")
**Posts on this page:** 1
**Showing post:** 4

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### Author: ![danlipsa](https://discourse.vtk.org/user_avatar/discourse.vtk.org/danlipsa/32/390_2.png) [@danlipsa](https://discourse.vtk.org/u/danlipsa)
#### Post date: [January 26, 2021, 7:58pm UTC](https://discourse.vtk.org/t/can-we-write-out-the-old-vtk-4-2-file-format-with-vtk-9/5066/4 "2021-01-26T19:58:12Z")

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This is likely the change that caused the bump in version number and incompatibility.

[https://discourse.vtk.org/t/upcoming-changes-to-vtkcellarray/2066](https://discourse.vtk.org/t/upcoming-changes-to-vtkcellarray/2066)

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